A semiconductor device includes: a base layer of a first conductivity type, a
barrier
layer of a first conductivity type formed on the base layer, a well layer of a
second conductivity type formed on the barrier layer; a trench formed from the
surface of the well layer to such a depth as to reach a region in the vicinity
of a junction surface between the barrier layer and the base layer, a gate electrode
formed in the trench via a gate insulating film, a contact layer of the second
conductivity type selectively formed in a surface portion of the well layer, a
source layer of the first conductivity type selectively formed in the surface portion
of the well layer so as to contact a side wall of the gate insulating film in the
trench and the contact layer, and a first main electrode formed so as to contact
the contact layer and the source layer, wherein assuming that a total sum of impurity
densities in the region of the barrier layer between the trenches is Qn, the Qn
has a relation of the following equation: Qn21012 cm-2.
