Patent ID: 8610168

Claim:
A semiconductor device comprising: an epitaxial layer of a first general conductivity type having a top surface and a bottom surface; a drift layer of the first general conductivity type formed in the epitaxial layer; a trench formed in the epitaxial layer so as to penetrate the epitaxial layer; a buffer layer of the first general conductivity type formed in the epitaxial layer so as to be at a sidewall of the trench and the bottom surface of the epitaxial layer; an embedded collector layer of a second general conductivity type covering the buffer layer an embedded insulation film disposed at a top portion of the trench, extending down along the sidewall of the trench and covering the collector layer on the bottom surface of the epitaxial layer; a polysilicon film covering the embedded insulation film so as to fill the trench at least partially; an insulation film covering the polysilicon film; and a semiconductor substrate attached to the polysilicon film through the insulation film.