In the structure of a semiconductor device of the present invention, a
first source electrode is connected to a conductive substrate through a
via hole, and a second source electrode is formed. Thus, even if a high
reverse voltage is applied between a gate electrode and a drain
electrode, electric field concentration likely to occur at an edge of the
gate electrode closer to the drain electrode can be effectively dispersed
or relaxed. Moreover, the conductive substrate is used as a substrate for
forming element formation layers, so that a via hole penetrating the
substrate to reach the backside thereof does not have to be formed in the
conductive substrate. Thus, with the strength necessary for the
conductive substrate maintained, the first source electrode can be
electrically connected to a backside electrode.