A semiconductor device according to an embodiment includes: a normally-off transistor having a first source, a first drain, and a first gate; a normally-on transistor having a second source electrically connected to the first drain, a second drain, and a second gate; a first capacitor having a first end and a second end, wherein the second end is electrically connected to the second gate; a first diode having a first anode electrically connected between the second end and the second gate, and a first cathode; a gate drive circuit electrically connected to the first gate and the first end; and a switch having a third end and a fourth end, wherein the third end is electrically connected to the first end.