A semiconductor device, including a semiconductor layer of a first conductivity type, and a parallel pn layer formed on a surface of the semiconductor layer. The parallel pn layer includes a plurality of first semiconductor regions of the first conductivity type, and a plurality of second semiconductor regions of a second conductivity type. The first and second semiconductor regions are alternatingly arranged in a direction parallel to the surface of the semiconductor layer. Each second semiconductor region has at least one first region that is a region having a group 18 element introduced therein.