COMPOSITE HIGH-K METAL GATE STACK FOR ENHANCEMENT MODE GAN SEMICONDUCTOR DEVICES

摘要

Enhancement mode gallium nitride (GaN) semiconductor devices having a composite high-k metal gate stack and methods of fabricating such devices are described. In an example, a semiconductor device includes a gallium nitride (GaN) channel region disposed above a substrate. A gate stack is disposed on the GaN channel region. The gate stack includes a composite gate dielectric layer disposed directly between the GaN channel region and a gate electrode. The composite gate dielectric layer includes a high band gap Group III-N layer, a first high-K dielectric oxide layer, and a second high-K dielectric oxide layer having a higher dielectric constant than the first high-K dielectric oxide layer. Source/drain regions are disposed on either side of the GaN channel region.