GaN metal oxide semiconductor diodes were demonstrated utilizing Sc2O3 as the gate oxide. Sc2O3 was grown at 100degreesC on MOCVD grown n-GaN layers in a molecular beam epitaxy system, using a scandium elemental source and an electron cyclotron resonance oxygen plasma. Ar/Cl-2 based discharges were used to remove Sc2O3, to expose the underlying n-GaN for ohmic metal deposition in an inductively coupled plasma system. Electron beam deposited Ti/Al/Pt/Au and Pt/Au were utilized as ohmic and gate metallizations, respectively. An interface trap density of 5 x 10(11) eV(-1) cm(-2) was obtained with the Terman method. Conductance-voltage measurements were also used to estimate the interface trap density and a slightly higher value was obtained as compared to the Terman method. Results of capacitance measurements at elevated temperature (up to 300degreesC) indicated the presence of deep states near the interface. (C) 2002 The Electrochemical Society.