Nitride semiconductor device

A nitride semiconductor device comprising:

• a semiconductor layer including a nitride semiconductor;
• a source electrode provided on a major surface of the semiconductor layer and forming ohmic contact with the semiconductor layer;
• a drain electrode provided on the major surface, forming ohmic contact with the semiconductor layer and separated from the source electrode;
• a first gate electrode provided on the major surface between the source electrode and the drain electrode, the first gate electrode being configured to operate in a normally-on mode in receiving an AC bias voltage;
• and
• a second gate electrode provided on the major surface between the source electrode and the first gate electrode.

A nitride semiconductor device comprising:

• a semiconductor layer;
• a source electrode provided on a major surface of the semiconductor layer and forming ohmic contact with the semiconductor layer;
• a drain electrode provided on the major surface, forming ohmic contact with the semiconductor layer and separated from the source electrode;
• a first gate electrode provided on the major surface between the source electrode and the drain electrode, the first gate electrode being configured to operate in a normally-on mode in receiving an AC bias voltage;
• and
• a second gate electrode provided on the major surface between the source electrode and the first gate electrode,
• the semiconductor layer including:
• a carrier running layer;
• and
• a carrier supply layer provided on the carrier running layer and supplying carriers to the carrier running layer,
• a polarization charge amount in the carrier supply layer being larger than a doping amount in the carrier supply layer, and
• the source electrode, the drain electrode, the first gate electrode, and the second gate electrode being provided on the carrier supply layer.