Hetero junction field effect transistor and method of fabricating the same

A hetero junction field effect transistor, comprising:

• a channel layer of a nitride based, group III-V compound semiconductor;
• a hetero characteristic improvement layer of a nitride based, group III-V compound semiconductor overlying and physically contacting said channel layer;
• a first layer of a nitride based, group III-V compound semiconductor, overlying and physically contacting said hetero characteristic improvement layer;
• a second layer of a nitride based, group III-V compound semiconductor containing a rare earth element, overlying and physically contacting said first layer;
• a pair of third layers of a nitride based, group III-V compound semiconductor, overlying and physically contacting said second layer, said third layers being spaced from each other;
• a two dimensional electron gas layer provided between said channel layer and said hetero characteristic improvement layer;
• a gate electrode disposed between said third layers on at least a region of said second layer;
• and
• a source electrode overlying one of said third layers and a drain electrode overlying an other of said third layers.