A semiconductor device, which is a diode, includes the following: an n cathode layer, which is an n-type region, disposed in a surface layer of a semiconductor substrate; a p cathode layer, which is a p-type region, disposed in the surface layer; and a cathode electrode, which is a metal electrode, in contact with both of the n cathode layer and the p cathode layer. The cathode electrode includes a first metal layer in contact with both of the n cathode layer and the p cathode layer, and a second metal layer disposed on the first metal layer. A contact surface between the first metal layer and the second metal layer has an oxygen concentration lower than the oxygen concentration of a contact surface between the first metal layer, and the n cathode layer and the p cathode layer.