Field effect transistor

A field effect transistor, comprising:

• a non-doped diamond layer having a hydrogen-terminated surface;
• first and second p+ diamond layers formed on the non-doped diamond layer and sandwiching a hydrogen-terminated region;
• a source electrode formed on the first p+ diamond layer and made of metal;
• a drain electrode formed on the second p+ diamond layer and made of metal;
• an insulating layer formed on the hydrogen-terminated region of the non-doped diamond layer;
• and
• a gate electrode formed on the insulating layer,
• a mutual conductance being equal to or higher than 0.5 mS/mm at room temperatures, even after an X-ray is applied with a dosage of 1 kGy,
• wherein the field effect transistor further comprises a recovery electrode, which is an independent electrode different from the source electrode, the drain electrode, and the gate electrode, and is configured to recover circuit characteristics of the field effect transistor.