A semiconductor device includes a first semiconductor layer of a first conductivity type, a second semiconductor layer formed in contact with the first semiconductor layer, and a third semiconductor layer of a second conductivity type formed in contact with the second semiconductor layer, the first semiconductor layer provided with a first semiconductor region at a given distance from an interface between the first semiconductor layer and the second semiconductor layer, and an impurity concentration of the first semiconductor region higher than an impurity concentration of the first semiconductor layer except where the first semiconductor region is formed.