Patent ID: 7429506

Claim:
A method of forming a compound semiconductor device comprising: forming a gate insulator layer overlying a compound semiconductor substrate; defining an active device region within the compound semiconductor substrate; forming ohmic contacts to the compound semiconductor substrate proximate opposite sides of the active device region, the ohmic contacts having portions thereof that overlap with portions of the gate insulator layer within the active device region, the overlapping portions ensuring avoidance of an undesirable gap formation between an edge of the ohmic contact and a corresponding edge of the gate insulator layer; and forming a gate metal contact electrode on the gate insulator layer in a region between the ohmic contacts, wherein subsequent to forming the ohmic contacts and prior to forming the gate metal contact electrode, the method further comprising annealing the gate insulator layer/compound semiconductor interface with a water vapor anneal to reduce a density of interface states (D it ) therein to a desired level, the method further comprising: forming a protective layer overlying the gate insulator layer subsequent to formation of the gate insulator layer and prior to defining the active device region, wherein forming ohmic contacts proximate opposite sides of the active device region further includes the ohmic contacts having a portion thereof that overlaps with the protective layer and the gate insulator layer; the method further comprising: removing the protective layer in a region substantially between the ohmic contacts to expose the gate insulator layer subsequent to formation of the ohmic contacts and prior to annealing with the water vapor anneal, wherein a portion of the protective layer remains under the ohmic contacts in the overlapping regions of the ohmic contacts; and forming a replacement protective layer, subsequent to the annealing with the water vapor anneal, in the region substantially between the ohmic contacts to cover the gate insulator layer previously exposed by the protective layer removal, wherein the gate metal contact electrode is formed through an opening in the replacement protective layer at a desired location of the gate metal contact electrode.