Patent ID: 7262478

Claim:
A semiconductor device comprising: a single-crystal semiconductor substrate of a first conductivity type; a first insulator film selectively covering a first principal surface of the substrate, the first insulator film having an opening; a first semiconductor region of the first conductivity type in contact with the substrate in the opening of the first insulator film; a second semiconductor region of a second conductivity type on the first insulator film outside the opening thereof; a third semiconductor region of the first conductivity type in the second semiconductor region; a second insulator film covering the first semiconductor region, the second semiconductor region, and the third semiconductor region; a polycrystalline semiconductor region on the second insulator film; a first electrode in contact with both the second semiconductor region and the third semiconductor region; a third insulator film between the first electrode and the polycrystalline semiconductor region; a fourth semiconductor region of the second conductivity type along a second principal surface of the substrate; and a second electrode in contact with the fourth semiconductor region.