A first semiconductor layer extends from the element region to the element-termination region, and functions as a drain of the MOS transistor. A second semiconductor layer extends, below the first semiconductor layer, from the element region to the element-termination region. A third semiconductor layer extends from the element region to the element-termination region, and is in contact with the second semiconductor layer to function as a drift layer of the MOS transistor. A distance between a boundary between the first semiconductor layer and the field oxide film, and the end portion of the third semiconductor layer on the fifth semiconductor layer side in the element region is smaller than that between a boundary between the first semiconductor layer and the field oxide layer and an end portion of the third semiconductor layer on the fifth semiconductor layer side in the element-termination region.