Conductivity-modulation metal oxide semiconductor field effect transistor

Abstract

A conductivity-modulation MOSFET employs a substrate of an N type conductivity as its N base. A first source layer of a heavily-doped N type conductivity is formed in a P base layer formed in the N base. A source electrode electrically conducts the P base and the source. A first gate electrode insulatively covers a channel region defined by the N.sup.+ source layer in the P base. A P drain layer is formed on an opposite substrate surface. An N.sup.+ second source layer is formed in a P type drain layer by diffusion to define a second channel region. A second gate electrode insulatively covers the second channel region, thus providing a voltage-controlled turn-off controlling transistor. A drain electrode of the MOSFET conducts the P type drain and second source. When the turn-off controlling transistor is rendered conductive to turn off the MOSFET a 'shorted anode structure' is temporarily formed wherein the N type base is short-circuited to the drain electrode, whereby case, the flow of carriers accumulated in the N type base into the drain electrode is facilitated to accelerate dispersion of carriers upon turn-off of the transistor.