Patent ID: 8058131

Claim:
A method of producing a semiconductor integrated circuit device, comprising the steps of: (a) forming a semiconductor structure comprising a tunnel insulating film covering a memory cell region of a substrate and a gate insulating film covering a logic device region of the substrate; (b) depositing a silicon film on the semiconductor structure formed in said step (a) so that the silicon film covers the tunnel insulating film in the memory cell region and the gate insulating film in the logic device region; (c) forming a first gate electrode in the memory cell region by selectively patterning the silicon film with the silicon film being left in the logic device region; (d) forming a protection oxide film so that the protection oxide film covers the first gate electrode in the memory cell region and the silicon film in the logic device region; (e) forming diffusion regions on both sides of the first gate electrode in the memory cell region by performing ion implantation of an impurity element into the substrate with the first gate electrode and the silicon film being employed as masks; (f) forming a second gate electrode in the logic device region by patterning the silicon film; and (g) forming diffusion regions in the logic device region by performing ion implantation with the second gate electrode being employed as a mask, whereby a nonvolatile memory device is formed in the memory cell region and a semiconductor device is formed in the logic device region.