Patent ID: 8304858

Claim:
A semiconductor device comprising: a supporting substrate; a semiconductor layer of a first conductivity type above a main surface of said supporting substrate; a first base region of a second conductivity type in a surface of said semiconductor layer; a buffer region of the first conductivity type spaced apart from said first base region in a lateral direction; an emitter region of the first conductivity type in a surface of said first base region; a collector region of the second conductivity type in a surface of said buffer region; a base contact diffusion region of the second conductivity type in the surface of said first base region; a gate insulating film on said semiconductor layer; and a gate electrode on said gate insulating film; wherein said first base region under said emitter region and at an end of said gate electrode has a point where an impurity concentration of the second conductivity type becomes maximum, and a length in a lateral direction from said point to an end of said first base region is not smaller than a length in the vertical direction from said point to an underside portion of said base region.