A semiconductor device has a first wiring extending in a first direction on a nitride semiconductor layer. A source electrode is electrically connected to the first wiring and extends in a second direction. A drain electrode extends in the second direction and includes a first and second portion extending in the second direction, spaced from each other in the first direction. An element isolation region is in the second nitride semiconductor layer between the first and second portions. A third portion extends in the second direction on the first and second portions. A gate electrode extends in the second direction on the second nitride semiconductor layer between the source electrode and the drain electrode. The portion includes holes therein aligned with each other along the second direction with the spacing between adjacent holes in the second direction increasing with increasing distance in the second direction from the first wiring.