A semiconductor device has a first conductivity-type semiconductor substrate, second conductivity-type channel regions, and second conductivity-type thinning-out regions. The channel regions and the thinning-out regions are formed adjacent to a substrate surface of the semiconductor substrate. Further, a hole stopper layer is formed in each of the thinning-out regions to divide the thinning-out region into a first part adjacent to the substrate surface and a second part adjacent to a bottom of the thinning-out region. The hole stopper layer has an area density of equal to or less than 4.0×1012 cm−2 to permit a depletion layer to punch through the hole stopper layer, thereby to restrict breakdown properties from being decreased.