Patent ID: 7105910

Claim:
A semiconductor device comprising: a semiconductor substrate including a first semiconductor layer, an insulation layer and a second semiconductor layer, which are laminated in this order; a trench penetrating both of the second semiconductor layer and the insulation layer and reaching the first semiconductor layer; a third semiconductor layer; and first and second electrodes, wherein the second semiconductor layer is disposed on a principal surface of the substrate, and the first semiconductor layer is disposed on a backside of the substrate, wherein the trench has a ring shape on the principal surface so that a part of the second semiconductor layer and a part of the insulation layer are surrounded with the trench, wherein the third semiconductor layer is disposed in the trench through a first insulation film disposed on a sidewall of the trench so that the third semiconductor layer contacts the first semiconductor layer at a bottom of the trench, wherein the first electrode is disposed on the principal surface of the substrate through a second insulation film, and electrically connects to the third semiconductor layer through a contact hole, and wherein the second electrode is disposed on the principal surface of the substrate through the second insulation film, and electrically connects to the part of the second semiconductor layer surrounded by the trench through another contact hole.