Compound semiconductor device and manufacturing method

A compound semiconductor device comprising:

• an electron transit layer;
• an electron supply layer formed over the electron transit layer;
• a first recessed portion and a second recessed portion formed in the electron supply layer;
• a chemical compound semiconductor layer including impurities that buries the first recessed portion and the second recessed portion and covers over the electron supply layer;
• a gate electrode formed over the electron supply layer between the first recessed portion and the second recessed portion;
• a source electrode formed over the chemical compound semiconductor layer which buries the first recessed portion;
• and
• a drain electrode formed over the chemical compound semiconductor layer which buries the second recessed portion,
• wherein, in the chemical compound semiconductor layer under the source electrode and the drain electrode, a concentration of impurities near the first and second recess portion is higher than a concentration of impurities near the gate electrode, and
• an insulating film is formed directly above the electron supply layer and directly below the chemical compound semiconductor layer.