Dynamic type semiconductor memory device

Claim 2

A dynamic type semiconductor memory device comprising: a plurality of memory cells each consisting of a MOS transistor and a capacitor; plural pairs of bit lines each pair of which consists of first and second bit lines for supplying data to said plurality of memory cells; a first sense amplifier, arranged for each of said plural pairs of bit lines, for amplifying a bit line signal; a pair of data input/output lines, consisting of first and second data input/output lines, for extracting data from said plural pairs of bit lines; a second sense amplifier, arranged for each of said plural pairs of bit lines and consisting of first and second driver MOS transistors gates of which are connected to a pair of bit lines and a third activating MOS transistor rendered conductive simultaneously when or immediately after said first sense amplifier is activated, for amplifying signals of said pair of data input/output lines in a data reading operation; first and second column selecting transistors which are inserted between said pair of data input/output lines and said second sense amplifier and gates of which are connected to a column selecting line; a first write transistor one current path of which is connected to said first bit line and the other current path of which is connected to one output terminal of said second sense amplifier, said first write transistor being turned on in a data writing operation; and a second write transistor one current path of which is connected to said second bit line and the other current path of which is connected to the other output terminal of said second sense amplifier, said second write transistor being turned on in a data writing operation.

Claim 3

The memory device according to claim 1, wherein said first sense amplifier for amplifying a bit lin signal is a CMOS sense amplifier including a first flip-flop consisting of two n-channel MOS transistors and a second flip-flop consisting of two p-channel MOS transistors, said first and second driver MOS transistors of said second sense amplifier for amplifying a data input/output line signal and said third activating MOS transistor are n-channel MOS transistors, said first and second column selecting transistors are n-channel MOS transistors, and said first and second write MOS transistors are n-channel MOS transistors.

Claim 4

The memory device according to claim 1, wherein said first sense amplifier for amplifying a bit line a signal is a CMOS sense amplifier including a first flip-flop consisting of two n-channel MOS transistors and a second flip-flop consisting of two p-channel MOS transistors, said first and second MOS transistors of said second sense amplifier for amplifying a data input/output line signal and the third activating MOS transistor are p-channel MOS transistors, said first and second column selecting transistors are p-channel MOS transistors, and said first and second write transistors are p-channel MOS transistors

Claim 5

A dynamic type semiconductor memory device comprising: a plurality of memory cells each consisting of a MOS transistor and a capacitor; plural pairs of bit lines each pair of which consists of first and second bit lines for supplying data to said plurality of memory cells; a first sense amplifier, arranged for each of said plural pairs of bit lines, for amplifying a bit line signal; a pair of data input/output lines, consisting of first and second data input/output lines, for extracting data from said pairs of bit lines; a second sense amplifier, arranged for each of said plural pairs of bit lines and consisting of first and second driver LOS transistors gates of which are connected to a pair of bit lines, activated simultaneously when or immediately after said first sense amplifier is activated, for amplifying signals of said pair of data input/output lines; first and second column selecting transistors which are inserted between said pair of data input/output lines and said second sense amplifier and gates of which are connected to a column selecting line; a first write transistor one current path of which is connected to said first bit line and the other current path of which is connected to one output terminal of said second sense amplifier, said first write transistor being turned on in a data writing operation; and a second write transistor one current path of which is connected to said second bit line and the other current path of which is connected to the other output terminal of said second sense amplifier, said second write transistor being turned on in a data writing operation.

Claim 6

A dynamic type semiconductor memory device comprising: a plurality of memory cells each consisting of a MOS transistor and a capacitor; plural pairs of bit lines each pair of which consists of first and second bit lines for supplying data to said plurality of memory cells; a first sense amplifier, arranged for each of said plural pairs of bit lines, for amplifying a bit line signal; a pair of data input/output lines, consisting of first and second data input/output lines, for extracting data from said pairs of bit lines; a second sense amplifier, arranged for each of said plural pairs of bit lines and consisting of first and second driver LOS transistors gates of which are connected to a pair of bit lines, activated simultaneously when or immediately after said first sense amplifier is activated, for amplifying signals of said pair of data input/output lines; first and second column selecting transistors which are inserted between said pair of data input/output lines and said second sense amplifier and gates of which are connected to a column selecting line; a first write transistor one current path of which is connected to said first bit line and the other current path of which is connected to one output terminal of said second sense amplifier, said first write transistor being turned on in a data writing operation; and a second write transistor one current path of which is connected to said second bit line and the other current path of which is connected to the other output terminal of said second sense amplifier, said second write transistor being turned on in a data writing operation.

Claim 7

The memory device according to claim 4, wherein said first sense amplifier is a CMOS sense amplifier including a first flip-flop consisting of two n-channel MOS transistors and a second flip-flop consisting of two p-channel MOS transistors, and first and second driver MOS transistors of said second sense amplifier are n-channel MOS transistors sources of which are connected to each other, the common source of said n-channel MOS transistors being connected to a signal line for activating said first flip-flop.

Claim 8

The memory device according to claim 4, wherein said first sense amplifier is a CMOS sense amplifier including a first flip-flop consisting of two n-channel MOS transistors and a second flip-flop consisting of two p-channel MOS transistors, and first and second driver MOS transistors, of said second sense amplifier are p-channel MOS transistors sources of which are connected to each other, the common source of said n-channel MOS transistors being connected to a signal line for activating said second flip-flop.

Claim 9

A dynamic type semiconductor memory device comprising: a plurality of memory cells each consisting of a MOS transistor and a capacitor; plural pairs of bit lines each pair of which consists of first and second bit lines for supplying data to said plurality of memory cells; a first sense amplifier, arranged for each of said plural pairs of bit lines, for amplifying a bit line signal; a pair of data input/output lines, consisting of first and second data input/output lines, for extracting data from said plural pairs of bit lines a second sense amplifier, arranged for each of said plural pairs of bit lines and consisting of first and second driver MOS transistors gates of which are connected to a pair of bit lines, third and fourth load MOS transistors, and a fifth activating MOS transistor rendered conductive simultaneously when or immediately after said first sense amplifier is activated, for amplifying signals of said pair of data input/output lines in a data reading operation; first and second column selecting transistor which are inserted between said pair of data input/output lines and said second sense amplifier and gates of which are connected to a column selecting line; a first write transistor one current path of which is connected to said first bit line and the other current path of which is connected to one output terminal of said second sense amplifier, said first write transistor being turned on in a data writing operation; and a second write transistor one current path of which is connected to said second bit line and the other current path of which is connected to the other output terminal of said second sense amplifier, said second write transistor being turned on in a data writing operation.

Claim 10

A dynamic type semiconductor memory device comprising: a plurality of memory cells each consisting of a MOS transistor and a capacitor; plural pairs of bit lines each pair of which consists of first and second bit lines for supplying data to said plurality of memory cells; a first sense amplifier, arranged for each of said plural pairs of bit lines, for amplifying a bit line signal; a pair of data input/output lines, consisting of first and second data input/output lines, for extracting data from said plural pairs of bit lines a second sense amplifier, arranged for each of said plural pairs of bit lines and consisting of first and second driver MOS transistors gates of which are connected to a pair of bit lines, third and fourth load MOS transistors, and a fifth activating MOS transistor rendered conductive simultaneously when or immediately after said first sense amplifier is activated, for amplifying signals of said pair of data input/output lines in a data reading operation; first and second column selecting transistor which are inserted between said pair of data input/output lines and said second sense amplifier and gates of which are connected to a column selecting line; a first write transistor one current path of which is connected to said first bit line and the other current path of which is connected to one output terminal of said second sense amplifier, said first write transistor being turned on in a data writing operation; and a second write transistor one current path of which is connected to said second bit line and the other current path of which is connected to the other output terminal of said second sense amplifier, said second write transistor being turned on in a data writing operation.

Claim 11

The memory device according to claim 7, wherein said first sense amplifier is a CMOS sense amplifier including a first flip-flop consisting of two n-channel MOS transistors and a second flip-flop consisting of two p-channel MOS transistors, said first and second driver MOS transistors and said fifth MOS transistor of the second sense amplifier are n-channel MOS transistors, and said third and fourth MOS transistors are p-channel MOS transistors, said column selecting transistors are n-channel transistors, and said pair of write transistors are n-channel MOS transistors.

Claim 12

The memory device according to claim 7, wherein said first sense amplifier is a CMOS sense amplifier including a first flip-flop consisting of two n-channel MOS transistors and a second flip-flop consisting of two p-channel MOS transistors, said first and second driver transistors and said fifth activating MOS transistor of said second sense amplifier are p-channel MOS transistors, and said third and fourth load MOS transistors are n-channel MOS transistors, said column selecting transistors are p-channel MOS transistors, and said pair of write transistors are p-channel MOS transistors.

Claim 13

The memory device according to claim 7, wherein said first sense amplifier is a CMOS sense amplifier including a first flip-flop consisting of two n-channel MOS transistors and a second flip-flop consisting of two p-channel MOS transistors, said first and second driver MOS transistors and said fifth activating MOS transistor of said second sense amplifier are n-channel MOS transistors, and said third and fourth transistors which are p-channel MOS transistors constitute a current mirror circuit, said column selecting transistors are n-channel MOS transistors, and said pair of write transistors are n-channel MOS transistors

Claim 14

The memory device according to claim 1, wherein said first sense amplifier is a CMOS sense amplifier including a first flip-flop consisting of two n-channel MOS transistors and a second flip-flop consisting of two p-channel MOS transistors, said first and second driver MO transistors and said fifth activating MOS transistor of said second sense amplifier are n-channel MOS transistors, and said third and fourth MOS transistors which are p-channel MOS transistors constitute a current mirror circuit, said column selecting transistors are p-channel MOS transistors, and said pair of write transistors are p-channel MOS transistors.

Claim 15

The memory device according to claim 7, wherein said first sense amplifier is a CMOS sense amplifier including a first flip-flop consisting of two n-channel MOS transistors and a second flip-flop consisting of two p-channel MOS transistors, said first and second driver MOS transistors and said fifth activating MOS transistor of said second sense amplifier are p-channel MOS transistors, and said third and fourth load MOS transistors which are n-channel MOS transistors constitute a current mirror circuit, said column selecting transistors are n-channel MOS transistors, and said pair of write transistors are n-channel MOS transistors.

Claim 16

The memory device according to claim 7, wherein said first sense amplifier is a CMOS sense amplifier including a first flip-flop consisting of two n-channel MOS transistors and a second flip-flop consisting of two p-channel MOS transistors, said first and second driver MOS transistors and said fifth activating MOS transistor of said second sense amplifier are p-channel MOS transistors, said third and fourth load MOS transistors which are n-channel MOS transistors constitute a current mirror circuit, said column selecting transistors are p-channel MOS transistors, and said pair of write transistors are p-channel MOS transistors.

Claim 17

A dynamic type semiconductor memory device comprising: a plurality of memory cells each consisting of a MOS transistor and a capacitor; plural pairs of bit lines each pair of which consists of first and second bit lines for supplying data to said plurality of memory cells; a first sense amplifier, arranged for each of said plural pairs of bit lines, for amplifying a bit line signal; a pair of data input/output lines, consisting of first and second data input/output lines, for extracting data from said plural pairs of bit lines; a second sense amplifier, arranged for each of said plural pairs of bit lines and consisting of first and second driver MOS transistors and third and fourth MOS transistors, for amplifying a signal of said pair of data input/output lines in a data reading operation; a through current suppressing MOS transistor inserted between a power source terminal and a current path of one of said first and second driver MOS transistors of said second sense amplifier for amplifying a data signal; a gate circuit for forming an AND signal of a signal of a column selecting line and a signal for defining a timing of activating a signal of a column selecting line, said gate circuit controlling said through current suppressing transistor to be rendered conductive on the basis of the AND signal; first and second column selecting transistors which are inserted between said pair of data input/output lines and said second sense amplifier and gates of which are connected to a column selecting line; a first write transistor one current path of which is connected to said first bit line and the other current path of which is connected to one output terminal of said second sense amplifier, said first write transistor being turned on in a data writing operation; and a second write transistor one current path of which is connected to said second bit line and the other current path of which is connected to the other output terminal of said second sense amplifier, said second write transistor being turned on in a data writing operation.

Claim 18

A dynamic type semiconductor memory device comprising: a plurality of memory cells each consisting of a MOS transistor and a capacitor; plural pairs of bit lines each pair of which consists of first and second bit lines for supplying data to said plurality of memory cells; a first sense amplifier, arranged for each of said plural pairs of bit lines, for amplifying a bit line signal; a pair of data input/output lines, consisting of first and second data input/output lines, for extracting data from said plural pairs of bit lines; a second sense amplifier, arranged for each of said plural pairs of bit lines and consisting of first and second driver MOS transistors and third and fourth MOS transistors, for amplifying a signal of said pair of data input/output lines in a data reading operation; a through current suppressing MOS transistor inserted between a power source terminal and a current path of one of said first and second driver MOS transistors of said second sense amplifier for amplifying a data signal; a gate circuit for forming an AND signal of a signal of a column selecting line and a signal for defining a timing of activating a signal of a column selecting line, said gate circuit controlling said through current suppressing transistor to be rendered conductive on the basis of the AND signal; first and second column selecting transistors which are inserted between said pair of data input/output lines and said second sense amplifier and gates of which are connected to a column selecting line; a first write transistor one current path of which is connected to said first bit line and the other current path of which is connected to one output terminal of said second sense amplifier, said first write transistor being turned on in a data writing operation; and a second write transistor one current path of which is connected to said second bit line and the other current path of which is connected to the other output terminal of said second sense amplifier, said second write transistor being turned on in a data writing operation.

Claim 19

A dynamic type semiconductor memory device comprising: a plurality of memory cells each consisting of MOS transistor and a capacitor; plural pairs of bit lines each pair of which consists of first and second bit lines for supplying data to said plurality of memory cells; a first sense amplifier, arranged for each of said plural pairs of bit lines, for amplifying a bit line signal; a pair of data input/output lines consisting of first and second data input/output lines for extracting data from said plural pairs of bit lines; a second sense amplifier, arranged for each of said plural pairs of bit lines and consisting of first and second driver MOS transistors gates of which are connected to a pair of bit lines, for amplifying a signal of said pair of data input/output lines in data reading operation; a column selecting line for enabling a signal from said first sense amplifier simultaneously when or immediately after said first sense amplifier is activated; a pair of column selecting transistors which ar inserted between said pair of data input/output lines and said second sense amplifier and gates of which are connected to said column selecting line; and a pair of write transistors which are inserted between said pair of data input/output lines and said pair of bit lines and turned on in a data writing operation.

Claim 20

A dynamic type semiconductor memory device comprising: a plurality of memory cells each consisting of MOS transistor and a capacitor; plural pairs of bit lines each pair of which consists of first and second bit lines for supplying data to said plurality of memory cells; a first sense amplifier, arranged for each of said plural pairs of bit lines, for amplifying a bit line signal; a pair of data input/output lines consisting of first and second data input/output lines for extracting data from said plural pairs of bit lines; a second sense amplifier, arranged for each of said plural pairs of bit lines and consisting of first and second driver MOS transistors gates of which are connected to a pair of bit lines, for amplifying a signal of said pair of data input/output lines in data reading operation; a column selecting line for enabling a signal from said first sense amplifier simultaneously when or immediately after said first sense amplifier is activated; a pair of column selecting transistors which ar inserted between said pair of data input/output lines and said second sense amplifier and gates of which are connected to said column selecting line; and a pair of write transistors which are inserted between said pair of data input/output lines and said pair of bit lines and turned on in a data writing operation.

Claim 21

A dynamic type semiconductor memory device comprising: a plurality of memory cells each consisting of a MOS transistor and a capacitor; plural pairs of bit lines each pair of which consists of first and second bit lines for supplying data to said plurality of memory cells; a first sense amplifier, arranged for each of said plural pairs of bit lines, for amplifying a bit line signal; a pair of data input/output lines, consisting of first and second data input/output lines, for extracting data from said pair of bit lines; a second sense amplifier, arranged for each of said plural pairs of bit lines and consisting of first and second driver MOS transistors gates of which are connected to a pair of bit lines, for amplifying a signal of said pair of data input/output lines simultaneously when said first sense amplifier is activated in a data reading operation, first and second column selecting transistors which are inserted between said pair of data input/output lines and said second sense amplifier and gates of which are connected to a column selecting line; a first write transistor one current path of which is connected to said first bit line and the other current path of which is connected to one output terminal of said second sense amplifier, said first write transistor being turned on in a data writing operation; and a second write transistor one current path of which is connected to said second bit line and the other current path of which is connected to the other output terminal of said second sense amplifier, said second write transistor being turned on in a data writing operation.

Claim 22

A dynamic type semiconductor memory device comprising: a plurality of memory cells each consisting of a MOS transistor and a capacitor; plural pairs of bit lines each pair of which consists of first and second bit lines for supplying data to said plurality of memory cells; a first sense amplifier, arranged for each of said plural pairs of bit lines, for amplifying a bit line signal; a pair of data input/output lines, consisting of first and second data input/output lines, for extracting data from said pair of bit lines; a second sense amplifier, arranged for each of said plural pairs of bit lines and consisting of first and second driver MOS transistors gates of which are connected to a pair of bit lines, for amplifying a signal of said pair of data input/output lines simultaneously when said first sense amplifier is activated in a data reading operation, first and second column selecting transistors which are inserted between said pair of data input/output lines and said second sense amplifier and gates of which are connected to a column selecting line; a first write transistor one current path of which is connected to said first bit line and the other current path of which is connected to one output terminal of said second sense amplifier, said first write transistor being turned on in a data writing operation; and a second write transistor one current path of which is connected to said second bit line and the other current path of which is connected to the other output terminal of said second sense amplifier, said second write transistor being turned on in a data writing operation.

Claim 23

A dynamic type semiconductor memory device comprising: `a plurality of memory cells each pair of which consist MOS transistor and a capacitor; plural pairs of bit lines each pair of which consist of first and second bit lines for supplying data to said plurality of memory cells; a first sense amplifier arranged for each of said pairs of bit lines, for amplifying a bit line signal; a pair of data input/output lines consisting of first and second data input/output lines, for extracting data from said pairs of bit lines; a second sense amplifier arranged for each of said plural pairs of bit lines and consisting of first and second driver MOS transistors gates of which are connected to be cross-coupled to said first and second bit lines, for extracting charges from said pair of data input/output lines in a data reading operation, and for amplifying a data input/output line signal; bit line pair selecting means, connected to gates of said first and second driver MOS transistors, for selecting one pair of bit lines from said plural pairs of bit lines in accordance with an address; first and second column selecting transistors which are inserted between said pair of data input/output lines and said second sense amplifier and gates of which are connected to a column selecting line; a first write transistor one current path of which is connected to one input terminal of said bit line pair selecting means and the other current path of which is connected to one output terminal of said second sense amplifier, said first write transistor being turned on in a data writing operation; and a second write transistor one current path of which is connected to the other input terminal of said bit line pair selecting means and the other current path of which is connected to the other output terminal of said second sense amplifier, said second write transistor being turned on in the data writing operation.

Claim 24

A dynamic type semiconductor memory device comprising: `a plurality of memory cells each pair of which consist MOS transistor and a capacitor; plural pairs of bit lines each pair of which consist of first and second bit lines for supplying data to said plurality of memory cells; a first sense amplifier arranged for each of said pairs of bit lines, for amplifying a bit line signal; a pair of data input/output lines consisting of first and second data input/output lines, for extracting data from said pairs of bit lines; a second sense amplifier arranged for each of said plural pairs of bit lines and consisting of first and second driver MOS transistors gates of which are connected to be cross-coupled to said first and second bit lines, for extracting charges from said pair of data input/output lines in a data reading operation, and for amplifying a data input/output line signal; bit line pair selecting means, connected to gates of said first and second driver MOS transistors, for selecting one pair of bit lines from said plural pairs of bit lines in accordance with an address; first and second column selecting transistors which are inserted between said pair of data input/output lines and said second sense amplifier and gates of which are connected to a column selecting line; a first write transistor one current path of which is connected to one input terminal of said bit line pair selecting means and the other current path of which is connected to one output terminal of said second sense amplifier, said first write transistor being turned on in a data writing operation; and a second write transistor one current path of which is connected to the other input terminal of said bit line pair selecting means and the other current path of which is connected to the other output terminal of said second sense amplifier, said second write transistor being turned on in the data writing operation.

Claim 25

A dynamic type semiconductor memory device comprising: a plurality of memory cells each consisting of a MOS transistor and a capacitor; plural pairs of bit lines each pair of which consist of first and second bit lines, for supplying data to said plurality of memory cells; a first sense amplifier arranged for each of said pairs of bit lines, for amplifying a bit line signal; a pair of data input/output lines consisting of first and second data input/output lines, for extracting data from said pairs of bit lines; a second sense amplifier arranged for each of said plural pairs of bit lines and consisting of first and second load MOS transistors and first and second driver MOS transistors gates of which are connected to be cross-coupled to said first and second bit lines, for extracting charges from said pair of data input/output lines in a data reading operation, and for amplifying a data input/output line signal; bit line pair selecting means, connected to gates of said first and second driver MOS transistors, for selecting one pair of bit lines from said plural pairs of bit lines in accordance with an address; first and second column selecting transistors which are inserted between said pair of data input/output lines and said second sense amplifier and gates of which are connected to a column selecting line; a first write transistor one current path of which is connected to one input terminal of said bit line pair selecting means and the other current path of which is connected to one output terminal of said second sense amplifier, said first write transistor being turned on in a data writing operation; and a second write transistor one current path of which is connected to the other input terminal of said bit line pair selecting means and the other current path of which is connected to the other output terminal of said second sense amplifier, said second write transistor being turned on in the data writing operation.

Claim 26

A dynamic type semiconductor memory device comprising: a plurality of memory cells each consisting of a MOS transistor and a capacitor; plural pairs of bit lines each pair of which consist of first and second bit lines, for supplying data to said plurality of memory cells; a first sense amplifier arranged for each of said pairs of bit lines, for amplifying a bit line signal; a pair of data input/output lines consisting of first and second data input/output lines, for extracting data from said pairs of bit lines; a second sense amplifier arranged for each of said plural pairs of bit lines and consisting of first and second load MOS transistors and first and second driver MOS transistors gates of which are connected to be cross-coupled to said first and second bit lines, for extracting charges from said pair of data input/output lines in a data reading operation, and for amplifying a data input/output line signal; bit line pair selecting means, connected to gates of said first and second driver MOS transistors, for selecting one pair of bit lines from said plural pairs of bit lines in accordance with an address; first and second column selecting transistors which are inserted between said pair of data input/output lines and said second sense amplifier and gates of which are connected to a column selecting line; a first write transistor one current path of which is connected to one input terminal of said bit line pair selecting means and the other current path of which is connected to one output terminal of said second sense amplifier, said first write transistor being turned on in a data writing operation; and a second write transistor one current path of which is connected to the other input terminal of said bit line pair selecting means and the other current path of which is connected to the other output terminal of said second sense amplifier, said second write transistor being turned on in the data writing operation.

Claim 27

A dynamic type semiconductor memory device comprising: a plurality of memory cells each consisting of a MOS transistor and a capacitor; plural pairs of bit lines each pair of which consist of first and second bit lines, for supplying data to said plurality of memory cells; a first sense amplifier arranged for each of said pairs of bit lines, for amplifying a bit line signal; a pair of data input/output lines consisting of first and second data input/output lines, for extracting data from said pairs of bit lines; a second sense amplifier arranged for each of said plural pairs of bit lines and consisting of first and second load MOS transistors and first and second driver MOS transistors gates of which are connected to be cross-coupled to said first and second bit lines, for extracting charges from said pair of data input/output lines in a data reading operation, and for amplifying a data input/output line signal; bit line pair selecting means, connected to gates of said first and second driver MOS transistors, for selecting one pair of bit lines from said plural pairs of bit lines in accordance with an address; a through current suppression MOS transistor arranged between one current path of said first and second driver MOS transistors of said second sense amplifier for amplifying a data signal and a power source terminal; first and second column selecting transistors which are inserted between said pair of data input/output lines and said second sense amplifier and gates of which are connected to a column selecting line; a first write transistor one current path of which is connected to one input terminal of said bit line pair selecting means and the other current path of which is connected to one output terminal of said second sense amplifier, said first write transistor being turned on in a data writing operation; and a second write transistor one current path of which is connected to the other terminal of said bit line pair selecting means and the other current path of which is connected to the other output terminal of said second sense amplifier, said second write transistor being turned on in the data writing operation.

Claim 28

A dynamic type semiconductor memory device comprising: a plurality of memory cells each consisting of a MOS transistor and a capacitor; plural pairs of bit lines each pair of which consist of first and second bit lines, for supplying data to said plurality of memory cells; a first sense amplifier arranged for each of said pairs of bit lines, for amplifying a bit line signal; a pair of data input/output lines consisting of first and second data input/output lines, for extracting data from said pairs of bit lines; a second sense amplifier arranged for each of said plural pairs of bit lines and consisting of first and second load MOS transistors and first and second driver MOS transistors gates of which are connected to be cross-coupled to said first and second bit lines, for extracting charges from said pair of data input/output lines in a data reading operation, and for amplifying a data input/output line signal; bit line pair selecting means, connected to gates of said first and second driver MOS transistors, for selecting one pair of bit lines from said plural pairs of bit lines in accordance with an address; a through current suppression MOS transistor arranged between one current path of said first and second driver MOS transistors of said second sense amplifier for amplifying a data signal and a power source terminal; first and second column selecting transistors which are inserted between said pair of data input/output lines and said second sense amplifier and gates of which are connected to a column selecting line; a first write transistor one current path of which is connected to one input terminal of said bit line pair selecting means and the other current path of which is connected to one output terminal of said second sense amplifier, said first write transistor being turned on in a data writing operation; and a second write transistor one current path of which is connected to the other terminal of said bit line pair selecting means and the other current path of which is connected to the other output terminal of said second sense amplifier, said second write transistor being turned on in the data writing operation.