Patent ID: 7456487

Claim:
A semiconductor device, comprising: a first base layer of a first conductivity type; a plurality of second base layers of a second conductivity type, provided on a part of a first surface of the first base layer; trenches formed on each side of the second base layers, and formed to be deeper than the second base layers; an emitter layer formed along the trench on a surface of the second base layers; a collector layer of the second conductivity type, provided below a second surface of the first base layer opposite to the first surface; an insulating film formed on an inner wall of the trench, the insulating film being thicker on a bottom of the trench than on a side surface of the trench; a gate electrode formed within the trench, and isolated from the second base layers and the emitter layer by the insulating film; a space section provided between the second base layers adjacent to each other; bottom semiconductor layers respectively provided below bottoms of the trenches, each bottom semiconductor layer covering a whole of the bottom surface of the corresponding trench, the bottom semiconductor layers having the first conductivity type higher in impurity concentration than the first base layer, a width between the bottom semiconductor layers adjacent to each other being smaller than a width between the trenches adjacent to each other so as to accumulate carriers in the first base layer.