Patent ID: 8501549

Claim:
A method of manufacturing a reverse blocking insulated gate bipolar transistor comprising: forming a ring-shaped diffusion layer of a second conductivity type composing a part of an isolation layer in a region of a first principal surface side of a semiconductor substrate of a first conductivity type; forming a main front surface structure including a MOS gate structure region and a voltage withstanding structure region in a region surrounded by the ring-shaped diffusion layer of the first principal surface side region; forming a tapered groove with a depth at least reaching a bottom surface of the ring-shaped diffusion layer from a second principal surface opposing the ring-shaped diffusion layer; forming a second conductivity type region on a side wall surface of the tapered groove; and forming a collector layer of the second conductivity type on the second principal surface to connect the second principal surface to the first principal surface through the second conductivity region, the tapered groove being formed by an anisotropic alkali etching process leaving the semiconductor substrate with a thickness of at least 60 μm between the bottom of the tapered groove and the first principal surface.