Patent ID: 7446009

Claim:
A method for manufacturing a semiconductor device, the method comprising: a first step of forming a conductive layer and a silicon film functioning as a base layer on a semiconductor substrate including an active region surrounded by an isolation film; a second step of forming an emitter electrode containing a first impurity on the silicon film above the active region; a third step of partially etching the silicon film using the emitter electrode as a mask; a fourth step of forming an insulative film entirely covering the semiconductor substrate and then etching back the insulative film to form a side wall film covering a side surface of the emitter electrode; a fifth step of introducing a second impurity into the conductive layer and the silicon film so that the second impurity reaches the active region to form an impurity region containing the second impurity in part of the conductive layer and part of the silicon film; and a sixth step of diffusing the first impurity contained in the emitter electrode into a surface of the silicon film to form in the silicon film a first region containing the first impurity and a second region free of the first impurity; wherein the third step includes forming the silicon film to have a reversed T-shape so that a contact surface between the first region and the emitter electrode is located above a lower surface of the side wall film when the fourth step is completed; and the sixth step includes forming the first and second regions in the silicon film so that at least part of the second region is positioned between the conductive layer and the side wall film and is in contact with both the conductive layer and the side wall film.