A semiconductor device and method of manufacturing the same includes an n−-single crystal silicon substrate, with an oxide film selectively formed thereon. On the oxide film, gate polysilicon is formed. The surface of the gate polysilicon is covered with a gate oxide film whose surface is covered with a cathode film doped in an n-type with an impurity concentration higher than that of the substrate as an n−-drift layer. In the cathode film, a section in contact with the substrate becomes an n+-buffer region with a high impurity concentration, next to which a p-base region is formed. Next to the p-base region, an n+-source region is formed. On the cathode film, an interlayer insulator film is selectively formed on which an emitter electrode is formed. A semiconductor device such as an IGBT is obtained with a high rate of acceptable products, an excellent on-voltage to turn-off loss tradeoff and an excellent on-voltage to breakdown voltage tradeoff.