Semiconductor device with self-aligned gate and field plate and method of fabrication therefor

A semiconductor device comprising:

• a semiconductor substrate comprising an upper surface and a channel;
• one or more lower dielectric layers disposed on the upper surface of the semiconductor substrate, wherein a source opening, a drain opening, a gate opening, and a field plate opening extend through the one or more lower dielectric layers to the semiconductor substrate, wherein the gate opening is between the source opening and the drain opening, and the field plate opening is between the gate opening and the drain opening;
• a conformal dielectric layer disposed over the one or more lower dielectric layers and into at least the gate opening and the field plate opening, wherein the conformal dielectric layer includes first portions formed on sidewalls of the gate opening, second portions formed on sidewalls of the field plate opening, and a third portion formed on the semiconductor substrate at a bottom extent of the field plate opening;
• gate spacers disposed on the first portions of the conformal dielectric layer;
• a gate electrode disposed in the gate opening in contact with the gate spacers and the semiconductor substrate;
• and
• a field plate disposed in the field plate opening in contact with the second and third portions of the conformal dielectric layer.