A semiconductor device capable of suppressing the occurrence of a punch-through phenomenon is provided. A first n-type conductive layer (2′) is formed on a substrate (1′). A p-type conductive layer (3′) is formed thereon. A second n-type conductive layer (4′) is formed thereon. On the under surface of the substrate (1′), there is a drain electrode (13′) connected to the first n-type conductive layer (2′). On the upper surface of the substrate (1′), there is a source electrode (11′) in ohmic contact with the second n-type conductive layer (4′), and a gate electrode (12′) in contact with the first n-type conductive layer (2′), p-type conductive layer (3′), the second n-type conductive layer (4′) through an insulation film (21′). The gate electrode (12′) and the source electrode (11′) are alternately arranged. The p-type conductive layer (3′) includes In.