PROBLEM TO BE SOLVED: To provide a semiconductor device having a high breakdown voltage.SOLUTION: The semiconductor device comprises: a first electrode; a first semiconductor layer of a first conductivity type; a second semiconductor layer of the first conductivity type, having a lower impurity concentration than that of the first semiconductor layer; a first semiconductor region of a second conductivity type, provided on a part of the second semiconductor layer; a second semiconductor region of the second conductivity type, being in contact with the first semiconductor region; a third semiconductor region of the second conductivity type, provided on a part of the first semiconductor region; and a second electrode provided on the first semiconductor region, the second semiconductor region, and the third semiconductor region. The impurity concentration in a surface in contact with the second electrode in the third semiconductor region is higher than that in the first semiconductor region and that in a surface in contact with the second electrode in the second semiconductor region. The thickness of the second semiconductor layer sandwiched between the first semiconductor region and the first semiconductor layer is thinner than the thickness of the second semiconductor layer sandwiched between the second semiconductor region and the first semiconductor layer.