A method of manufacturing a semiconductor device includes forming a dummy gate wiring layer having a side surface and an upper surface on a first area of one major surface of a substrate, the major surface of the substrate including the first area and a second area, thereafter, forming a semiconductor film on the second area of the major surface of the substrate by using epitaxial growth, the semiconductor film having a thickness smaller than a thickness of the dummy gate wiring layer, and forming, on the semiconductor film, a gate sidewall which is made of an insulator and covers the side surface of the dummy gate wiring layer.