A semiconductor device having an alternating conductivity type layer improves
the
tradeoff between the on-resistance and the breakdown voltage and facilitates increasing
the current capacity by reducing the on-resistance while maintaining a high breakdown
voltage. The semiconductor device includes a semiconductive substrate region, through
which a current flows in the ON-state of the device and that is depleted in the
OFF-state. The semiconductive substrate region includes a plurality of vertical
alignments of n-type buried regions 32 and a plurality of vertical alignments
of p-type buried regions. The vertically aligned n-type buried regions and the
vertically aligned p-type buried regions are alternately arranged horizontally.
The n-type buried regions and p-type buried regions are formed by diffusing respective
impurities into highly resistive n-type layers 32a laminated one
by one epitaxially.