Oxide semiconductor device, and, method for manufacturing oxide semiconductor device

The object of the present invention is to improve the resistance to pressure when applying a reverse voltage, while preventing the diffusion of a different material in a discharge key interface. An oxide semiconductor device is provided with an epitaxial layer of n-type gallium oxide (2), a p-type oxide semiconductor layer (5) consisting of an oxide of a material which is different from a material for the epitaxial layer of gallium oxide, a layer of dielectric material (7) which is formed to cover at least a portion of a side surface of the semi layer an oxide conductor, an anode electrode (4) and a cathode electrode (3), a pn heterojunction being formed between a lower surface of the oxide semiconductor layer and the substrate of gallium oxide (1) or between a lower surface of the oxide semiconductor layer (5a) and the gallium oxide epitaxial layer (2).