A dielectric structure for a nitride semiconductor device and a method of forming the same. A semiconductor device includes at least one semiconductor layer. The at least one semiconductor layer includes a gallium nitride semiconductor material. The semiconductor device also includes an oxidized layer disposed over the at least one semiconductor layer. The oxidized layer includes an oxidized form of the gallium nitride semiconductor of the at least one semiconductor layer. A silicon oxide layer is disposed over the oxidized layer. A gate is disposed over the silicon oxide layer.