Patent ID: 8809939

Claim:
A semiconductor device, comprising, on a substrate: a semiconductor region including at least three semiconductor layers of different dielectric constants; a gate insulating film which covers the semiconductor region; and a gate electrode formed on the gate insulating film, wherein the dielectric constants of the at least three semiconductor layers are set to become larger in order from the substrate side, wherein one of the semiconductor layers forming a channel region is in contact with the gate insulating film, wherein an intermediate layer of the semiconductor layers including silicon germanium as a main component thereof has a film thickness of 30 nm or less, wherein the semiconductor layer forming the channel region has a film thickness of 3 to 40 nm so as to allow carriers to run on only the semiconductor layer including silicon germanium as the main component, and wherein the semiconductor layer having a maximum dielectric constant includes silicon germanium as a main component thereof, the intermediate semiconductor layer includes silicon germanium having a lower germanium concentration than that of the semiconductor layer having the maximum dielectric constant as a main component thereof, and the semiconductor layer closest to the substrate includes silicon as a main component thereof.