Insulated gate bipolar transistor, semiconductor device, method of manufacturing insulated-gate bipolar transistor, and method of manufacturing semiconductor device

Abstract

An insulated gate bipolar transistor, a semiconductor device using such a transistor, and manufacturing methods of these. The transistor, device, and method eliminate the necessity of connection to a freewheel diode used for bypassing a circulating current. In the transistor, device, and method the concentration of impurities of an N+ buffer layer that forms a junction with a P+ collector layer is increased so that it is possible to reduce an avalanche breakdown voltage of a parasitic diode formed by an N base layer and the P+ collector layer. Thus, the reverse voltage resistance of an IGBT is lowered to not more than 5 times the collector-emitter saturated voltage.