Mask-ROM manufacturing method

Claim 1

A mask-ROM manufacturing method characterized by comprising: a step (a) of insulatively forming a first conduc­tive layer on a semiconductor substrate of a first con­ductivity type; a step (b) of forming a first material film which is inactive on said first conductive layer; a step (c) of forming a second material film which is active on said first material film; a step (d) of patterning said second material film; a step (e) of increasing the volume of said second material film by altering the material of said second material film patterned; a step (f) of patterning said first material film with said second material film having an increased volume as a mask and forming windows for doping first impurity in said first material film; a step (g) of selectively doping impurity of a second conductivity type from said first impurity doping window into said substrate through said first conductive layer; a step (h) of selectively altering the material of the surface of said first conductive layer with said patterned first material film used as a mask to selec­tively form a material altered region on the surface of said first conductive layer; a step (i) of patterning said first conductive layer with said material altered region used as a mask to form first-layered gates and form second impurity doping windows in said first conductive layer; a step (j) of selectively doping impurity of the second conductivity type from said second impurity doping window into said substrate; a step (k) of insulatively forming a second conductive layer over said first conductive layer and substrate; and a step (l) of patterning said second conductive layer to form second-layered gates.