There is provided a semiconductor device structured so as to be mounted jointly
with other devices on one chip, and capable of controlling a large current in spite
of a small device area while having small on-resistance, thereby enabling a high
voltage resistance to be obtained. In the case of NLDMOS, the semiconductor device
comprises an N well layer, formed on a p-type semiconductor substrate, a P well
layer formed in the N well layer, a source electrode formed in a source trench
cavity within the P well layer, a gate electrode formed in at least one of gate
trench cavities within the P well layer, through the intermediary of an oxide film,
and a drain electrode formed in a drain trench cavity within the N well layer,
and further, N+ diffused layers are formed, around the source trench cavity, the
drain trench cavity, respectively.
