Patent ID: 7564075

Claim:
A semiconductor device comprising: a semiconductor substrate; a collector layer arranged on the semiconductor substrate; a conductive layer, arranged on the collector layer, for functioning as a base layer; a silicon film arranged on the conductive layer; an emitter electrode arranged on the silicon film and having a side surface; and a first film, having a lower surface, for covering the side surface of the emitter electrode, the first film provided as a diffusion barrier that prevents diffusion of impurities from the emitter electrode to the silicon film in a lateral direction, wherein: the silicon film includes a diffusion layer as a first region of the silicon film that contacts the emitter electrode and functions as an emitter layer, and a second region that is a region other than the diffusion layer; a contact surface between the diffusion layer and the emitter electrode is located at a level that is higher than that of the lower surface of the first film; and at least part of the second region of the silicon film is located between the conductive layer and the first film and is in contact with the conductive layer and the first film.