A semiconductor device according to an embodiment includes: a substrate; a first semiconductor layer formed on the substrate and having a strain; a second and a third semiconductor layers formed at a distance from each other on the first semiconductor layer, and having a different lattice constant from a lattice constant of the first semiconductor layer; a gate insulating film formed on a first portion of the first semiconductor layer, the first portion being located between the second semiconductor layer and the third semiconductor layer; and a gate electrode formed on the gate insulating film. At least one of outer surface regions of the second semiconductor layer and a second portion of the first semiconductor layer is a first silicide region, and at least one of outer surface regions of the third semiconductor layer and a third portion of the first semiconductor layer is a second silicide region, the second and third portions being located immediately below the second and third semiconductor layers respectively.