Conductive modulated MOSFET

Claim 1

A conductivity modulated metal oxide semiconductor field effect transistor, comprising: a first conductivity type region having a first surface; a high resistance semiconductor region of a second conductivity type having a second surface; a second conductivity type region provided between said first conductivity type region and said high resistance semiconductor region and having an impurity concentration higher than that of said high resistance semiconductor region; a base region of the first conductivity type which is formed in the second surface of said high resistance semiconductor region; a source region of the second conductivity type which is formed in said base region; a gate electrode formed at least on a gate insulating film which is formed on a channel region formed in said base region between said high resistance semiconductor region and said source region; a source electrode ohmic-contacting said source and base regions; and a drain electrode formed on said first surface of the first conductivity type region; wherein when a total channel width within a unit area (1 cm 2 ) of an active region is W(μm), an area of said high resistance semiconductor region which is formed beneath said gate electrode and is in direct contact with the gate insulating film within said unit area of the active region is SG(μm 2 ), a perimeter of said base region in contact with the high resistance semiconductor region, i.e., the perimeter of SG, within the 1 cm 2 unit area of the active region, in μm, is T(μm), a channel length is l(μm) and a thickness of said gate insulating film is d(μm), a condition (W·SG)/(T·l·d)<1.46×10 8 is satisfied; and wherein said active region is defined as a region including the base and source regions contacting the source electrode and the high resistance semiconductor region under the gate electrode.