Patent ID: 8193591

Claim:
A method for forming a semiconductor device on a substrate having a principal surface, the method comprising: forming a semiconductor layer on the principal surface of the substrate, wherein the semiconductor layer has an outer surface opposite the substrate; forming a first passivation layer on the outer surface of the semiconductor layer opposite the substrate by providing a layer comprising silicon and nitrogen; locally etching away portions of the first passivation layer and the semiconductor layer to thereby form a device mesa above the principal surface of the substrate, wherein the device mesa has an upper surface still covered by the first passivation layer and wherein the device mesa further has exposed lateral edges where the first passivation layer and the semiconductor layer has been removed; after the etching step, forming a second passivation layer at least over the first passivation layer on the upper surface of the device mesa and the exposed lateral edges of the device mesa, wherein the second passivation layer is a single and substantially contiguous layer that continuously extends across the entire upper surface of the device mesa and that also completely covers the exposed lateral edges of the device mesa; after forming the second passivation layer, providing source-drain vias and a gate via through the first and second passivation layers to the upper surface of the semiconductor layer on the device mesa; and forming conductors in the vias so as to provide ohmic contact to the semiconductor layer in the source-drain vias and a Schottky contact to the semiconductor layer in the gate via.