Semiconductor device

A semiconductor device having an active region and an inactive region that surrounds the active region, and comprising:

• a lateral switching device disposed in the active region and including
• a channel forming layer that is disposed on a substrate, includes a heterojunction structure having a first semiconductor layer made of a first GaN-based semiconductor forming a drift region and a second semiconductor layer made of a second GaN-based semiconductor having a band gap energy higher than a band gap energy of the first GaN-based semiconductor, and has a recessed portion provided in the second semiconductor layer,
• a gate structure portion that includes a gate insulating film disposed in the recessed portion and a MOS gate electrode disposed on the gate insulating film and serving as a gate electrode of a MOS structure,
• a source electrode and a drain electrode which are disposed on the second semiconductor layer in such a manner that the gate structure portion is interposed between the source electrode and the drain electrode,
• a third semiconductor layer that is disposed on the second semiconductor layer at a position away from the drain electrode between the gate structure portion and the drain electrode, and is made of a third GaN-based semiconductor not doped with an impurity,
• a fourth semiconductor layer that is disposed on the third semiconductor layer and is made of a fourth GaN-based semiconductor having a p-type, and
• a junction gate electrode that is brought into contact with the fourth semiconductor layer;
• a gate pad disposed in the inactive region and connected to the MOS gate electrode through a gate wire;
• a source pad disposed in the inactive region and connected to the source electrode through a source wire;
• and
• a drain pad disposed in the inactive region and connected to the drain electrode through a drain wire, wherein
• the junction gate electrode is electrically connected to the source electrode to have a same potential as a potential of the source electrode, and is disposed only in the active region.