Patent ID: 7659173

Claim:
A method for manufacturing an insulated-gate type field effect transistor, comprising the steps of: preparing a semiconductor substrate of which at least a part of one main surface has a first conductivity type; forming an isolation region for demarcating an element arrangement region corresponding to the part of one main surface of the semiconductor substrate; forming a gate insulating film on a semiconductor surface in the element arrangement region; forming a conductive material layer on the gate insulating film; forming a hard mask material layer above the gate insulating film via the conductive material layer; forming a resist layer on the hard mask material layer by a photolithography process in accordance with a desired gate electrode pattern; performing an etching process using the resist layer as a mask to the hard mask material layer to form a hard mask composed of a part of the hard mask material layer remaining in accordance with the gate electrode pattern; performing an anisotropic etching process using the resist layer as a mask to the conductive material layer to remain a part of the conductive material layer in accordance with the gate electrode pattern; removing the resist layer; performing an isotropic etching process using the hard mask as a mask to decrease a width of a remaining part of the conductive material layer so as to form a gate electrode layer composed of the remaining part of the conductive material layer of which width is decreased; and forming a source and a drain regions having a second conductivity type opposite to the first conductivity type respectively in one and another side of the gate electrode layer by performing an impurity ion doping process using a lamination of the gate insulating film, the gate electrode film and the hard mask and the isolation region as a mask, wherein an ion doping depth in a first part of each of the source and the drain regions under the mask where the hard mask is not overlapped with the gate electrode layer is shallower than an ion doping depth in a second part of each of the source and the drain regions that is not covered by the mask by doping the impurity ions to the first part of each of the source and the drain regions via the mask where the hard mask is not overlapped with the gate electrode layer.