Semiconductor device

A semiconductor device, comprising:

• a substrate;
• a first semiconductor layer arranged above the substrate;
• a second semiconductor layer arranged on the first semiconductor layer to generate a two-dimensional electronic gas in the first semiconductor layer in a vicinity of an interface between the second semiconductor layer and the first semiconductor layer;
• a source electrode and a drain electrode arranged on the second semiconductor layer and electrically connected to the two-dimensional electronic gas;
• a third semiconductor layer arranged on the second semiconductor layer between the source electrode and the drain electrode and including an acceptor impurity;
• a gate electrode arranged on the third semiconductor layer;
• and
• a guard ring arranged on the second semiconductor layer, wherein
• the second semiconductor layer defines a boundary between an element region in which a field-effect transistor is formed and an element separation region surrounding the element region,
• the field-effect transistor is formed of the first semiconductor layer, the second semiconductor layer, the third semiconductor layer, the gate electrode, the source electrode, and the drain electrode, and
• the guard ring is arranged in a peripheral part of the element region and includes
• a fourth semiconductor layer arranged on the second semiconductor layer and including an acceptor impurity, and
• a first electrode arranged on the fourth semiconductor layer and electrically connected to the source electrode or the two-dimensional electronic gas.