Semiconductor device with a field plate having a recessed region and an overhanging portion and method of fabrication therefor

A method of forming a semiconductor device, the method comprising:

• forming source and drain electrodes over an upper surface of a semiconductor substrate that includes a channel, wherein the source and drain electrodes are electrically coupled to the channel, and the channel extends between the source and drain electrodes;
• depositing a passivation layer over the upper surface of the semiconductor substrate by depositing a lower passivation sub-layer on the upper surface of the semiconductor substrate, and depositing an upper passivation sub-layer over the lower passivation sub-layer, wherein the lower passivation sub-layer is formed from a first dielectric material, and the upper passivation sub-layer is formed from a second dielectric material that is different from the first dielectric material;
• forming a first dielectric layer over the passivation layer;
• forming a first opening at least partially through the first dielectric layer and through the passivation layer between the source and drain electrodes;
• depositing a gate electrode over the semiconductor substrate between the source and drain electrodes, wherein the gate electrode includes a lower portion that extends into the first opening in the passivation layer to contact the semiconductor substrate;
• forming a second opening through the upper passivation sub-layer adjacent to the gate electrode, wherein the second opening does not extend through the lower passivation sub-layer, and the second opening is shallower than the first opening;
• and
• forming a conductive field plate adjacent to the gate electrode, wherein the conductive field plate includes a first portion with a recessed region that extends through the upper passivation sub-layer but does not extend through the lower passivation sub-layer, and an overhanging portion that extends over an upper surface of the first dielectric layer.