US Patent 9379191 High electron mobility transistor including an isolation region

A high electron mobility transistor (HEMT) includes a first III-V compound layer. A second III-V compound layer is disposed on the first III-V compound layer and is different from the first III-V compound layer in composition. A carrier channel is located between the first III-V compound layer and the second III-V compound layer. A source feature and a drain feature are disposed on the second III-V compound layer. A p-type layer is disposed on a portion of the second III-V compound layer between the source feature and the drain feature. A gate electrode is disposed on the p-type layer. The gate electrode includes a refractory metal. A depletion region is disposed in the carrier channel and under the gate electrode.