Patent ID: 8618602

Claim:
A semiconductor device comprising: a semiconductor substrate having an active region and first and second grooves, each of the first and second grooves extending across the active region, the first groove being wider in width than the second groove; a word line in the first groove, the word line comprising: a first gate insulating film covering inside walls of the first groove; and a first conductive film in the first groove, the first conductive film being separated by the first gate insulating film from the semiconductor substrate; an isolation region in the second groove, the isolation region being narrower in width than the word line and comprising: a second gate insulating film covering inside walls of the second groove; and a second conductive film in the second groove, the second conductive film being separated by the second gate insulating film from the semiconductor substrate; and a diffusion region in the active region, the diffusion region being between the first and second grooves, wherein the second conductive film is substantially the same in its top surface level as the first conductive film, and wherein the top surface levels of the first and second conductive film are shallower than a bottom surface level of the diffusion region.