Integrated gate assisted turn-off, amplifying gate thyristor with narrow lipped turn-off diode

Claim 1

An integrated amplifying gate thyristor with gate assist turn-off capability comprising: A. main and pilot thyristors disposed in a semiconductor body having first and second major surfaces, each thyristor having four impurity regions extending through the body between the major surfaces, said impurity regions of alternate conductivity-type disposed alteratively with PN junctions formed between adjacent regions, the two regions interior being cathode-base and anode-base regions, and the two regions adjoining the first and second major surfaces and adjoining the cathode-base and anode-base regions being cathode-emitter and anode-emitter regions, respectively; B. the cathode-base, anode-base and anode-emitter regions of the main and pilot thyristors being common to both thyristors; C. said common cathode-base region adjoining the first major surface between the cathode-emitter regions of the main and pilot thyristors such that the cathode-emitter regions thereof are spaced apart: D. a diode disposed in the semiconductor body adjacent the main thyristor formed by a cathode impurity region in the body adjoining the first major surface adjacent to and spaced from the separate cathode-emitter regions of the main and pilot thyristors and from the common cathode-base regions of the thyristors, said diode and said cathode-base region at the diode forming a transistor structure having a current gain less than the ratio of I FB /I g , where I FB is the forward anode current triggering the main thyristor into low impedance conducting state by applying a threshold negative gate assist current and an operating anode-cathode load potential, and I g is a specified gate assist turn-off current to turn-off the main thyristor; and said cathode region of said diode having a shallow impurity lip extending toward the cathode-emitter region of the main thyristor, said shallow lip having an area larger than the remainder of the cathode region and a depth less than about one-half of the remainder of the cathode region: E. cathode and anode electrodes positioned on said first and second major surfaces, respectively, to make ohmic contact with the cathode-emitter region of the main thyristor and the common anode-emitter region of the main and pilot thyristors; F. a gate electrode positioned on said first major surface to make ohmic contact with the common cathode-base region adjacent to and spaced from the cathode-emitter region of the pilot thyristor, and with the cathode region of the diode; and G. a floating electrode positioned on said first major surface adjacent to and spaced from the gate electrode to make ohmic contact with the common cathode-base region between the thyristors and the cathode-emitter region of the pilot thyristor.