A simplified manufacturing process stably produces a semiconductor device with high electrical characteristics, wherein platinum acts as an acceptor. Plasma treatment damages the surface of an oxide film formed on a n− type drift layer deposited on an n+ type semiconductor substrate. The oxide film is patterned to have tapered ends. Two proton irradiations are carried out on the n− type drift layer with the oxide film as a mask to form a point defect region in the vicinity of the surface of the n− type drift layer. Silica paste containing 1% by weight platinum is applied to an exposed region of the n− type drift layer surface not covered with the oxide film. Heat treatment inverts the vicinity of the surface of the n− type drift layer to p-type by platinum atoms which are acceptors. A p-type inversion enhancement region forms a p-type anode region.