NITRIDE SEMICONDUCTOR DEVICE

A nitride semiconductor device includes an electron transit layer, formed above a substrate, and an electron supply layer formed on the electron transit layer and having a larger band gap than the electron transit layer. A gate layer is formed on the electron supply layer and contains an acceptor impurity. A gate electrode is formed on the gate layer. A source electrode and a drain electrode are located at opposite sides of the gate layer and contact the electron supply layer. The gate electrode has a greater length than the gate layer in a first direction in which the source electrode, the gate layer, and the drain electrode are arranged. The gate electrode contacts an entire upper surface of the gate layer and extends from the gate layer toward at least one of the source electrode and the drain electrode.