Patent ID: 7374983

Claim:
A manufacturing method of a semiconductor device, comprising the steps of: forming a gate insulating film over an island-like semiconductor layer; forming a first conductive film to be a first gate electrode over the gate insulating film; forming a second conductive film to be a second gate electrode over the first conductive film; forming a tapered resist over the second conductive film; forming the second gate electrode to have a tapered shape by etching the resist and the second conductive film; doping an impurity element of one conductivity type at a first concentration to the semiconductor layer; etching the second gate electrode perpendicularly using the resist as a mask; doping the impurity element of one conductivity type at a lower concentration than the first concentration to the semiconductor layer; removing the resist; forming a silicon compound film over the second gate electrode; forming sidewalls on opposite sides of the second gate electrode by etching the silicon compound film; and forming the first gate electrode by etching the first conductive film using the second gate electrode and the sidewall as a mask.