Semiconductor device and method manufacturing the same

A semiconductor device includes: an n− type layer disposed on a first surface of a substrate; an n+ type region disposed on the n− type layer; a trench disposed on the n− type layer; a p type region disposed adjacent to a side surface of the trench and extending to a part under a lower surface of the trench; an auxiliary n+ type region disposed under the lower surface of the trench and disposed in the p type region; an auxiliary electrode disposed at the lower surface of the trench; a gate electrode separated from the auxiliary electrode and disposed on the lower surface of the trench; a source electrode disposed on the n+ type region; and a drain electrode disposed at a second surface of the substrate.