A diode 10 comprises an SOI substrate in which are stacked a semiconductor substrate 20, an insulator film 30, and a semiconductor layer 40. A bottom semiconductor region 60, an intermediate semiconductor region 53, and a surface semiconductor region 54 are formed in the semiconductor layer 40. The bottom semiconductor region 60 includes a high concentration of n-type impurity. The intermediate semiconductor region 53 includes a low concentration of n-type impurity. The surface semiconductor region 54 includes p-type impurity.