Semiconductor device with improved field plate

A method of forming a transistor device comprising:

• providing a semiconductor body;
• providing a spacer layer over at least a portion of a surface of the semiconductor body;
• and
• providing a field plate over at least a portion of the spacer layer, wherein providing the field plate comprises:
• providing a first current carrying layer;
• providing a refractory metal interposer layer over the first current carrying layer;
• and
• providing a second current carrying layer over the refractory metal interposer layer.

A transistor device comprising:

• a substrate;
• a nucleation layer over the substrate;
• a buffer layer over the nucleation layer;
• a barrier layer over the buffer layer;
• a spacer layer over at least a portion of the barrier layer;
• and
• a field plate over at least a portion of the spacer layer, wherein the field plate comprises:
• a first current carrying layer;
• a refractory metal interposer layer over the first current carrying layer;
• and
• a second current carrying layer over the refractory metal interposer layer.