Abstract
A nitride-based semiconductor device includes first and second nitride-based semiconductor layers, source and drain electrodes, and a gate structure. The gate structure includes at least one conductive layer and two or more doped nitride-based semiconductor layers. The at least one conductive layer includes a metal and is in contact with the second nitride-based semiconductor layer to form a metal-semiconductor junction therebetween. The two or more doped nitride-based semiconductor layers are in contact with the second nitride-based semiconductor layer and adjoin the conductive layer so as to form a contact interface with the second nitride-based semiconductor layer adjoining the metal-semiconductor junction.