Patent ID: 7709324

Claim:
A method of manufacturing a semiconductor device, comprising: covering second and third portions of a semiconductor layer with first and second stack structures, respectively, the first stack structure including a first gate insulating film and a first gate electrode material layer on the first gate insulating film, and the second stack structure including a second gate insulating film and a second gate electrode material layer on the second gate insulating film; selectively forming a trench in a first portion of the semiconductor layer after said covering the second and third portions; forming a third gate electrode material layer in the trench with an intervention of a third gate insulating film therebetween while covering the second and third portions of the semiconductor layer respectively with first and second stack structures; forming a fourth gate electrode material layer in contact respectively with the first, second and third gate electrode materials; and selectively removing the first, second and fourth gate electrode material layers to form first, second and third gate electrodes respectively on the first, second and third portions of the semiconductor layer, the first gate electrode comprising the third gate electrode material layer and a first part of the fourth gate electrode material layer, the second gate electrode comprising a part of the first gate electrode material layer and a second part of the fourth gate electrode material layer, and the third gate electrode comprising a part of the second gate electrode material layer and a third part of the fourth gate electrode material layer.