. "The lower P-type semiconductor region 14 is formed in the P???-type semiconductor substrate 15 and the N???-type semiconductor region 21 by diffusing a P-type dopant, such as boron (B), or gallium (Ga) in the surface region of the P???-type semiconductor region 15 to form a region, and then diffusing the P-type dopant toward the N???-type semiconductor region 21 at the time of epitaxial growth of" . . .