A field effect transistor includes a semiconductor stack formed on a substrate, and having a first nitride semiconductor layer and a second nitride semiconductor layer. A source electrode and a drain electrode are formed on the semiconductor stack so as to be separated from each other. A gate electrode is formed between the source electrode and the drain electrode so as to be separated from the source electrode and the drain electrode. A hole injection portion is formed near the drain electrode. The hole injection portion has a p-type third nitride semiconductor layer, and a hole injection electrode formed on the third nitride semiconductor layer. The hole injection electrode and the drain electrode have substantially the same potential.