A first insulator (710) having an opening within a central region (551)
is formed on a main surface (61S) of an epitaxial layer (610). Then,
p-type impurities are ion implanted through the opening of the first insulator
(710) and then heat treatment is carried out, thereby to form a p base layer
(621) in the main surface (61S). An insulating film is formed to
fill in the opening and then etched back, thereby to form a second insulator (720)
on a side surface (71W) of the first insulator (710). Under conditions
where the second insulator (720) is present, n-type impurities are ion implanted
through the opening and then heat treatment is carried out, thereby to form an
n+ source layer (630) in the main surface (61S) of the
p base layer (621).
