Patent ID: 8497553

Claim:
A semiconductor device, comprising: a first transistor that is a heterojunction field effect transistor (HFET) having a first ohmic electrode, a first gate electrode, and a second ohmic electrode; and a first protecting element that is connected between the first gate electrode and the first ohmic electrode, and establishes a current path that passes a current therethrough when an overvoltage is applied to the first gate electrode, wherein: the first protecting element includes a second transistor that is a normally-off HFET having a first protecting element ohmic electrode, a first protecting element gate electrode and a second protecting element ohmic electrode, the second protecting element ohmic electrode is connected to the first gate electrode, the first protecting element ohmic electrode is connected to the first ohmic electrode, and the first protecting element include a first threshold voltage adjusting circuit connected between the first protecting element gate electrode and the first protecting element ohmic electrode, the first threshold voltage adjusting circuit being configured to adjust a threshold voltage of the second transistor.