An anode electrode and a cathode electrode formed on a silicon semiconductor substrate, p-type layer formed next to the anode electrode, an n-type layer formed next to the cathode electrode by a V-group element being diffused, an n− layer formed between the p-type layer and the n-type layer, and an n-buffer layer formed between the n− layer and the n-type layer and containing oxygen are provided and an oxygen concentration in an area of a width of at least 30 μm from a surface on a side of the n-type layer of the cathode electrode toward the anode electrode is set to 1×1017 cm−3 or more and also the oxygen concentration of the n− layer in a position in contact with the p-type layer is set to less than 3×1017 cm−3.