Patent ID: 8587033

Claim:
A transistor device, comprising: a high electron mobility field effect transistor (HEMT) having a source, a drain, a gate, and a first insulator separating the gate from a compound semiconductor body of the transistor device, the HEMT operable to switch on and conduct current from the source to the drain when a voltage applied to the gate exceeds a threshold voltage of the HEMT; and a protection device monolithically integrated with the HEMT so that the protection device shares the source and the drain with the HEMT and further comprises a gate electrically connected to the source and a second insulator separating the gate of the protection device from the compound semiconductor body, the protection device operable to conduct current from the drain to the source when the HEMT is switched off and a reverse voltage between the source and the drain exceeds a threshold voltage of the protection device, the threshold voltage of the protection device being less than the difference of the threshold voltage of the HEMT and a gate voltage used to turn off the HEMT, wherein the first insulator is thinner under the gate of the HEMT than the second insulator under the gate of the protection device.