Patent ID: 7723171

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; forming a first gate insulating film on a pair of opposing side surfaces of the first projection; depositing a first gate electrode material on the mask material and device isolation insulating film; planarizing the first gate electrode material by using the mask material and device isolation insulating film as stoppers; etching away the mask material formed in the second region; forming a second gate insulating film in the first and second regions; and removing the second gate insulating film formed in the first region.