Nitride semiconductor device and method for fabricating the same

1. A nitride semiconductor FET comprising:

a first nitride semiconductor layer formed over a substrate;

a second nitride semiconductor layer formed on the first nitride semiconductor layer and having a wider band gap than the first nitride semiconductor layer;

a third nitride semiconductor layer which is formed on the second nitride semiconductor layer and which includes a control region doped with magnesium and high resistive region formed around the control region and containing hydrogen combined with magnesium;

a gate electrode formed on the control region;

a source electrode formed on a first side of the gate electrode; and

a drain electrode formed on a second side of the gate electrode which is different from the first side of the gate electrode,

wherein the control region and the high resistive region contain a group III element, and an amount of the group III element in the control region is substantially the same as amount of the group III element in the high resistive region, and

the high resistive region is disposed between the gate electrode and the source electrode, and between the gate electrode and the drain electrode.

2. The nitride semiconductor FET of claim 1 , further comprising:

the high resistive region is thinner than the control region.

3. The nitride semiconductor FET of claim 1 , wherein the control region has p-type conductivity.