Claimed and disclosed is a method of manufacturing a semiconductor device, the method comprising the steps of forming a dummy gate on a semiconductor substrate, forming a source-drain diffusion region by introducing an impurity into the semiconductor substrate having the dummy gate as a mask, removing the dummy gate to form an opening, and forming a gate electrode within the opening with a gate insulating film formed below the gate electrode. The dummy gate is further formed by coating the semiconductor substrate with a polymer having a higher carbon content than hydrogen content so as to form a polymer film, forming a photoresist pattern on the polymer film, and transferring the pattern shape of the photoresist pattern onto the polymer film.