Patent ID: 7244972

Claim:
A semiconductor device, comprising at least one field effect transistor, the field effect transistor including: a first semiconductor layer; a first active layer provided on the first semiconductor layer, an uppermost portion of the first active layer being a nitride-containing layer and a main portion of the first active layer being a second semiconductor layer having a composition expressed as Si 1−x−y Ge x C y (0<x<1, 0≦y<1, x+y<0); and a gate electrode provided on the first active layer; wherein the nitride-containing layer is made of at least one material selected from carbon nitride (CN), aluminum nitride (AlN) gallium nitride (GaN), germanium nitride (GeN), silicon carbon nitride (SiCN) and germanium carbon nitride (GeCN), wherein the first semiconductor layer has a composition expressed as Si 1−x−y Ge x C y (0≦x<1, 0≦y<1); and the second semiconductor layer has a composition expressed as Si 1-y C y (0<y<1).