Abstract: According to one embodiment, a semiconductor device includes a semiconductor layer of a first conductivity type, first semiconductor pillar regions of the first conductivity type and second semiconductor pillar regions of a second conductivity type, a semiconductor region of the first conductivity type, a base region of the second conductivity type, a source region, a first main electrode, a second main electrode and a control electrode. The second semiconductor pillar region includes a plurality of semiconductor regions of the second conductivity type. A difference is provided between peak values of impurity concentration profiles of an uppermost and a lowermost semiconductor regions of the plurality of semiconductor regions, and in the alternately arranging direction of the first and second semiconductor pillar regions, maximum width of the uppermost semiconductor region is generally equal to or narrower than maximum width of the lowermost semiconductor region.