US Patent 7821035 ED inverter circuit and integrate circuit element including the same

A second semiconductor layer of a second nitride-based compound semiconductor with a wider bandgap formed on a first semiconductor layer of a first nitride-based compound semiconductor with a smaller bandgap includes an opening, on which a gate insulating layer is formed at a portion exposed through the opening. A first source electrode and a first drain electrode formed across a first gate electrode make an ohmic contact to the second semiconductor layer. A second source electrode and a second drain electrode formed across a second gate electrode that makes a Schottky contact to the second semiconductor layer make an ohmic contact to the second semiconductor layer.