A semiconductor device of an embodiment includes a first region including a first portion of a semiconductor layer having first and second planes, a first trench, a first gate electrode, a first source electrode and a drain electrode; a second region adjacent to the first region in a first direction and including a second portion of the semiconductor layer, a second trench, a second gate electrode, a second source electrode on the first plane side, and the drain electrode; a third region adjacent to the first region in a second direction crossing the first direction and including a third portion of the semiconductor layer, a third trench, a third gate electrode, a third source electrode on the first plane side, and the drain electrode; a first gate electrode pad connected to the first gate electrode; and a second gate electrode pad connected to the second and third gate electrodes.