Patent ID: 8188511

Claim:
A semiconductor device comprising: a substrate; a drift layer of a first conductivity type on the substrate with a first insulator film therebetween; a base layer of a second conductivity type in the drift layer; a first layer of the first conductivity type in the base layer; a gate electrode over the surface of the base layer, between the drift layer and the first layer with a gate insulator film therebetween; a second insulator film, a portion of the second insulator film disposed on a surface of the drift layer; a first electrode electrically connected to both the base layer and the first layer, a portion of the first electrode being disposed on the second insulator film; a buffer layer of the first conductivity type in the drift layer and spaced apart from the base layer; a second layer of one of the first or second conductivity type in the buffer layer; a second electrode electrically connected to the second layer; and a trench between the base layer and the second layer, wherein the trench is filled with the second insulator film, and wherein the distance between the bottom of the trench and the insulator film on the substrate being 1 μm or more and 75% or less of the thickness of the drift layer; wherein the first layer is an emitter layer, the second layer is a collector layer of the second conductivity type, the first electrode is an emitter electrode, and the second electrode is a collector electrode; wherein the emitter electrode extends from one side of the trench, over and across the trench, to the other side of the trench; and wherein the emitter electrode is not directly electrically connected to the drift layer and the emitter electrode is not directly electrically connected to the buffer layer.