Compound semiconductor device and method of manufacturing the same

A power supply apparatus comprising

• a compound semiconductor device, which comprises:
• a substrate;
• a compound semiconductor stacked structure formed over the substrate;
• and
• a gate electrode, a source electrode and a drain electrode formed on or above the compound semiconductor stacked structure, wherein the compound semiconductor stacked structure comprises:
• an electron channel layer;
• and
• a nitride semiconductor layer which comprises an electron supply layer formed over the electron channel layer, and
• an indium (In) fraction at a surface of the nitride semiconductor layer in each of a region between the gate electrode and the source electrode and a region between the gate electrode and the drain electrode is lower than an indium (In) fraction at a surface of the nitride semiconductor layer in a region below the gate electrode.

An amplifier comprising

• a compound semiconductor device, which comprises:
• a substrate;
• a compound semiconductor stacked structure formed over the substrate;
• and
• a gate electrode, a source electrode and a drain electrode formed on or above the compound semiconductor stacked structure, wherein the compound semiconductor stacked structure comprises:
• an electron channel layer;
• and
• a nitride semiconductor layer which comprises an electron supply layer formed over the electron channel layer, and
• an indium (In) fraction at a surface of the nitride semiconductor layer in each of a region between the gate electrode and the source electrode and a region between the gate electrode and the drain electrode is lower than an indium (In) fraction at a surface of the nitride semiconductor layer in a region below the gate electrode.

A method of manufacturing a compound semiconductor device comprising:

• forming a compound semiconductor stacked structure over a substrate;
• and
• forming a gate electrode, a source electrode and a drain electrode on or above the compound semiconductor stacked structure;
• wherein
• the forming the compound semiconductor stacked structure further comprises:
• forming an electron channel layer;
• and
• forming a nitride semiconductor layer which comprises an electron supply layer over the electron channel layer, and
• an indium (In) fraction at a surface of the nitride semiconductor layer in each of a region between the gate electrode and the source electrode and a region between the gate electrode and the drain electrode is lower than an indium (In) fraction at a surface of the nitride semiconductor layer in a region below the gate electrode.