Compound semiconductor device and method of manufacturing the same

A method of manufacturing a compound semiconductor device, the compound semiconductor device comprising:

• a substrate;
• an electron transit layer formed above the substrate;
• an electron supply layer formed above the electron transit layer;
• and
• a source electrode, a drain electrode, and a gate electrode formed between the source electrode and the drain electrode, which are formed above the electron supply layer,
• wherein a first insulating film is formed, at least, directly in contact with a first side surface of the drain electrode which faces the gate electrode and a second insulating film is formed, at least, directly in contact with a second side surface of the gate electrode which faces the drain electrode, and the first insulating film is not in contact with the second side surface, and
• wherein a two-dimensional electron gas concentration at a portion corresponding to below the second insulating film is made lower than a two-dimensional electron gas concentration at a portion corresponding to below the first insulating film between the electron transit layer and the electron supply layer.