Gallium Nitride-Based Device with Step-Wise Field Plate and Method Making the Same

A semiconductor structure, comprising:

• a first III-V compound layer on a substrate;
• a second III-V compound layer directly on the first III-V compound layer, the second III-V compound layer being different from the first III-V compound layer in composition and further including aluminum;
• a gate stack on the second III-V compound layer;
• a source feature and a drain feature disposed on the second III-V compound layer;
• and
• a field plate disposed over the gate stack and electrically connected to the source feature, wherein the field plate includes at least three segments with a step-wise structure.

A method, comprising:

• forming a first III-V compound layer on a substrate;
• forming a second III-V compound layer on the first III-V compound layer, wherein the second III-V compound layer is different from the first III-V compound layer in composition and further includes aluminum;
• forming a gate stack on the second III-V compound layer;
• forming a source feature and a drain feature on the second III-V compound layer and interposed by the gate stack;
• and
• forming a field plate over the gate stack and electrically connected to the source feature, wherein the field plate includes at least three segments configured in a step-wise structure.