Semiconductor device and method of manufacturing the semiconductor device

A semiconductor device comprising:

• a substrate;
• a semiconductor multilayer structure supported by the substrate;
• a first nitride transistor provided in a first area of the semiconductor multilayer structure;
• and
• a second nitride transistor provided in a second area different from the first area in the semiconductor multilayer structure, wherein:
• the semiconductor multilayer structure comprises:
• a first nitride semiconductor layer;
• a second nitride semiconductor layer;
• a third nitride semiconductor layer having a band gap narrower than a band gap of the second nitride semiconductor layer;
• a fourth nitride semiconductor layer having an electric resistance value larger than an electric resistance value of the third nitride semiconductor layer, and
• a semi-insulating nitride semiconductor layer located between the substrate and the first nitride semiconductor layer,
• the first nitride semiconductor layer is located between the substrate and the second nitride semiconductor layer,
• the third nitride semiconductor layer is located between the second nitride semiconductor layer and the fourth nitride semiconductor layer,
• the second nitride semiconductor layer and the third nitride semiconductor layer are located between the first nitride semiconductor layer and the fourth nitride semiconductor layer,
• the first nitride transistor comprises:
• part of the first nitride semiconductor layer, part of the second nitride semiconductor layer, part of the third nitride semiconductor layer, and part of the fourth nitride semiconductor layer, the parts of the first to fourth semiconductor layers being located in the first area of the semiconductor multilayer structure;
• a first gate electrode electrically connected to the part of the first nitride semiconductor layer;
• a first source electrode electrically connected to one of two portions in the third nitride semiconductor layer, and a first drain electrode electrically connected to the other one of the two portions in the third nitride semiconductor layer, the two portions being spaced by a predetermined distance;
• and
• a first substrate electrode electrically connected to the part of the fourth nitride semiconductor layer,
• the second nitride transistor comprising:
• part of the first nitride semiconductor layer, part of the second nitride semiconductor layer, part of the third nitride semiconductor layer, and part of the semi-insulating nitride semiconductor layer, the parts of the first to third nitride semiconductor layers being located in the second area of the semiconductor multilayer structure;
• a second substrate electrode electrically connected to the part of the semi-insulating nitride semiconductor layer;
• a second source electrode electrically connected to one of two portions in the first nitride semiconductor layer, and a second drain electrode electrically connected to the other one of the two portions in the first nitride semiconductor layer, the two portions being spaced by a predetermined distance;
• and
• a second gate electrode electrically connected to the part of the third nitride semiconductor layer, and
• the second nitride semiconductor layer has the band gap wider than a band gap of the first nitride semiconductor layer.