A method of manufacturing a semiconductor device includes forming a trench in an interlayer dielectric film on the semiconductor substrate, the trench reaching a semiconductor substrate and having a sidewall made of silicon nitride film; depositing a gate insulation film made of a HfSiO film at a temperature within a range of 200 degrees centigrade to 260 degrees centigrade, so that the HfSiO film is deposited on the semiconductor substrate which is exposed at a bottom surface of the trench without depositing the HfSiO film on the silicon nitride film; and filling the trench with a gate electrode made of metal.