A semiconductor device includes an active layer having a first side surface, a
second side surface perpendicular to the first side surface and a third side surface
opposite to the second side surface, a first gate electrode arranged on the first
side surface with a first gate insulating film disposed therebetween, a second
gate electrode formed of a material different from that of the first gate electrode
and arranged on the second side surface with a second gate insulating film disposed
therebetween, and a third gate electrode formed of a material different from that
of the first gate electrode and arranged on the third side surface with a third
gate insulating film disposed therebetween.
