A semiconductor device includes a field effect transistor and a strain generating layer to apply a stress to a channel region of the field effect transistor. The strain generating layer contains at least one of oxygen and nitrogen of 1.0×1018 cm−3 to 5.0×1019 cm−3, or alternatively, the strain generating layer contains self-interstitial atoms and/or vacancies of 1.0×1018 cm−3 to 5.0×1019 cm−3. In the latter case, at least a portion of the self-interstitial atoms and/or the vacancies exist as a cluster.