Semiconductor device

A semiconductor device comprising:

• a semiconductor layer disposed on a surface of a substrate and causing an oxidation reaction and a reduction reaction when irradiated with light;
• an oxidation catalyst layer that is disposed on part of a surface of the semiconductor layer, forms along with the semiconductor layer a Schottky junction, and oxidizes an oxidation target substance;
• a reduction catalyst layer that is disposed on part of the surface of the semiconductor layer where the oxidation catalyst layer is not disposed so as to be separated from the oxidation catalyst layer, forms along with the semiconductor layer an ohmic junction, and reduces a reduction target substance;
• and
• an insulation layer that is disposed on entirety of the surface of the semiconductor layer where none of the oxidation catalyst layer and the reduction catalyst layer is disposed so as to be in contact with the oxidation catalyst layer and the reduction catalyst layer, and transmits the light with which the semiconductor layer is irradiated,
• wherein the insulation layer comprises an oxide is configured to cover portions of the semiconductor layer not covered by the oxidation catalyst layer and the reduction layer and is configured to suppress a deterioration reaction in the semiconductor layer without preventing the semiconductor layer from absorbing the light,
• wherein the surface of the semiconductor layer is entirely coated with the oxidation catalyst layer, the reduction catalyst layer, and the insulation layer, and
• wherein the reduction catalyst layer is a layer that is a laminate of a 25 nm platinum thin film that is layered on a 25 nm titanium thin film.