Semiconductor integrated circuit device including a semiconductor device having a stable threshold characteristic

Abstract

A semiconductor integrated circuit device includes a substrate, a nonvolatile memory device formed in a memory cell region of the substrate, and a semiconductor device formed in a device region of the substrate. The nonvolatile memory device has a multilayer gate electrode structure including a tunnel insulating film and a floating gate electrode formed thereon. The floating gate electrode has sidewall surfaces covered with a protection insulating film. The semiconductor device has a gate insulating film and a gate electrode formed thereon. A bird's beak structure is formed of a thermal oxide film at an interface of the tunnel insulating film and the floating gate electrode, the bird's beak structure penetrating into the floating gate electrode along the interface from the sidewall faces of the floating gate electrode, and the gate insulating film is interposed between the substrate and the gate electrode to have a substantially uniform thickness.