Gate turn-off device with high turn-off gain

Claim 1

A monolithically integrated turn-off semiconductor switch device comprising: a pair of main terminals for carrying load current; a control terminal which enables said device to be turned ON by a signal current of one polarity and turned OFF by a signal current of opposite polarity; first non-regenerative switch means comprising a power transistor formed vertically in a substrate by first, second, and third regions of alternating conductivity types; a diode formed by fourth and fifth regions of opposite conductivity types in series with the aforementioned regions of said vertical transistor but separated therefrom by a sixth region of said substrate doped to provide low minority carrier lifetimes therein and prevent vertical regenerative action between said diode and said vertical transistor; said fourth region of said diode being disposed on a bottom surface of said substrate and ohmically connected to one of said main terminals and; said third region of said vertical transistor being disposed on the top surface of said substrate and ohmically connected to the other of said main terminals; second non-regenerative switching means comprising a transistor of opposite conductivity type to said vertical transistor laterally formed in said substrate by said first region of said vertical transistor, and by a seventh and an eighth regions of alternating conductivity types, said seventh region being disposed on the top surface of said substrate and ohmically connected to said one of said main terminals, and said eighth region also being disposed on the top surfaces of said substrate; said first and second individually non-regenerative switching means being parasitically isolated from each other on said substrate, but regeneratively coupled to supply each other's base drive current and form a regenerative current loop therebetween, and said control terminal being connected to said regenerative coupling such that application of signal current of said one polarity initiates regenerative loop current between said first and second individually non-regenerative switching means; and third non-regenerative switching means comprising a third transistor monolithically integrated laterally in said substrate and parasitically isolated from said vertical and lateral transistors and said diode and comprising ninth, tenth and eleventh regions of alternating conductivity types, said third switching means having ohmic connections to said regenerative loop and said other of said main terminals such that upon application of base drive signal current thereto being rendered conducting to shunt current from said regenerative loop to thereby render said first switching means non-conductive to turn off said device.