A process for manufacturing a semiconductor device, wherein a semiconductor layer is formed on a body of semiconductor material; a first mask is formed on the semiconductor layer; a first conductive region is implanted in the body using the first mask; a second mask is formed laterally and complementarily to the first mask, at least in a projection in a plane parallel to the surface of the body; a second conductive region is implanted in the body using the second mask, in an adjacent and complementary position to the first conductive region; spacers are formed on the sides of the second mask region, to form a third mask aligned to the second mask; and, using the third mask, portions of the semiconductor layer are removed to form a gate region.