In this study, the rare earth erbium oxide (Er2O3) was deposited using an electron beam onto an AlGaN/GaN heterostructure to fabricate metal-oxide-semiconductor high-electron-mobility transistors (MOS-HEMTs) that exhibited device performance superior to that of a conventional HEMT. Under similar bias conditions, the gate leakage currents of these MOS-HEMT devices were four orders of magnitude lower than those of conventional Schottky gate HEMTs. The measured sub-threshold swing (SS) and the effective trap state density (N-t) of the MOS-HEMT were 125 mV/decade and 4.3x10(12) cm(-2), respectively. The dielectric constant of the Er2O3 layer in this study was 14, as determined through capacitance-voltage measurements. In addition, the gate-source reverse breakdown voltage increased from -166 V for the conventional HEMT to -196 V for the Er2O3 MOS-HEMT. (C) 2013 Elsevier B.V. All rights reserved.