Nitride semiconductor device

A nitride semiconductor device comprising:

• a substrate;
• a first nitride semiconductor layer above the substrate;
• a first p-type nitride semiconductor layer above the first nitride semiconductor layer;
• a first opening penetrating through the first p-type nitride semiconductor layer to the first nitride semiconductor layer;
• an electron transport layer and an electron supply layer provided in stated order from a substrate side, the electron transport layer and the electron supply layer covering an upper portion of the first p-type nitride semiconductor layer and the first opening;
• a gate electrode above the electron supply layer and covering the first opening;
• a source electrode away from the gate electrode and in contact with the electron supply layer;
• a second opening penetrating through the electron supply layer and the electron transport layer to the first p-type nitride semiconductor layer;
• a potential fixing electrode in contact with the first p-type nitride semiconductor layer at a bottom part of the second opening;
• and
• a drain electrode below the substrate,
• wherein the potential fixing electrode includes a material in Schottky contact with the first p-type nitride semiconductor layer.

A nitride semiconductor device comprising:

• a substrate;
• a first nitride semiconductor layer above the substrate;
• a first p-type nitride semiconductor layer above the first nitride semiconductor layer;
• a first opening penetrating through the first p-type nitride semiconductor layer to the first nitride semiconductor layer;
• an electron transport layer and an electron supply layer provided in stated order from a substrate side, the electron transport layer and the electron supply layer covering an upper portion of the first p-type nitride semiconductor layer and the first opening;
• a gate electrode above the electron supply layer and covering the first opening;
• a source electrode away from the gate electrode and in contact with the electron supply layer;
• a second opening penetrating through the electron supply layer and the electron transport layer to the first p-type nitride semiconductor layer;
• a potential fixing electrode in contact with the first p-type nitride semiconductor layer at a bottom part of the second opening;
• and
• a drain electrode below the substrate, wherein:
• a contact portion of the first p-type nitride semiconductor layer which is in contact with the potential fixing electrode has a thickness greater than or equal to 50 percent of a thickness of a non-contact portion of the first p-type nitride semiconductor layer which is not in contact with the potential fixing electrode,
• the thickness of the non-contact portion is greater than or equal to 400 nm, and
• the potential fixing electrode includes a material in Schottky contact with the first p-type nitride semiconductor layer.