Provided is a technique of securing reliability of a gate insulating film, as much as in a Si power MOSFET, in a semiconductor device in which a semiconductor material having a larger band gap than silicon is used, and which is typified by, for example, an SiC power MOSFET. In order to achieve this object, in the in the SiC power MOSFET, the gate electrode GE is formed in contact with the gate insulating film GOX, and is formed of the polycrystalline silicon film PF1 having the thickness equal to or smaller than 200 nm, and the polycrystalline silicon film PF2 formed in contact with the polycrystalline silicon film PF1, and having any thickness.