Patent ID: 7371644

Claim:
A semiconductor device fabrication method, comprising: depositing a mask material on a semiconductor substrate; patterning the mask material and forming a trench in a surface portion of the semiconductor substrate by etching, thereby forming a first projection in a first region, and a second projection wider than the first projection in a second region; burying a device isolation insulating film in the trench; etching away a predetermined amount of the device isolation insulating film formed in the first region; etching away the mask material formed in the second region; forming a first gate insulating film on a pair of opposing side surfaces of the first projection, and a second gate insulating film on an upper surface of the second projection; depositing a first gate electrode material on the device isolation insulating film, mask material, and second gate insulating film; planarizing the first gate electrode material by using as stoppers the mask material formed in the first region and the device isolation insulating film formed in the second region; depositing a second gate electrode material on the mask material, first gate electrode material, and device isolation insulating film; and patterning the first and second gate electrode materials, thereby forming a first gate electrode in the first region, and a second gate electrode in the second region.