A semiconductor device includes a first conduction-type semiconductor substrate, a first semiconductor region of a first conduction-type formed on the semiconductor substrate, a second semiconductor region of a second conduction-type formed on a surface of the first semiconductor region, a third semiconductor region of the second conduction-type formed to be separated from the second semiconductor region on the surface of the first semiconductor region, a fourth semiconductor region of the second conduction-type formed to be separated from the second semiconductor region and the third semiconductor region on the surface of the first semiconductor region, and a first electrode connected to the second semiconductor region and the third semiconductor region.