Patent ID: 9013006
Filing Date: 2015-04-21
Classification: H01L

Abstract:
1. A method for manufacturing a semiconductor device including a field-effect transistor, comprising steps of: (a) forming a trench in a semiconductor substrate; (b) forming a first insulating film in the trench; (c) forming an intrinsic polycrystalline silicon film over the first insulating film; (d) introducing impurities of a first conductivity type into the intrinsic polycrystalline silicon film to form a first conductive film; (e) after the step (d), etching the first conductive film so as to provide a portion of the first conductive film in a lower part of the trench, thereby to form a first gate electrode of the field-effect transistor; (f) forming a second insulating film in the trench, wherein the second insulating film is disposed above the first insulating film and the first gate electrode; (g) forming a doped polycrystalline silicon film of the first conductivity type, having higher impurity concentration than the first gate electrode, over the second insulating film; and (h) etching the doped polycrystalline silicon film so as to provide a portion of the doped polycrystalline silicon film in an upper part of the trench, thereby to form a second gate electrode of the field-effect transistor.