Enhancement mode, high electron mobility PHEMT-based metal oxide semi conductor field effect transistor (MOSFET) devices have been fabricated using an oxide high-kappa gate dielectric stack developed using molecular beam epitaxy. A template layer of Ga2O3, initially deposited on the surface of the III-V device unpins the GaAs Fermi level while the deposition of a bulk ternary (GdxGa1-x)(2)O-3 layer forms the highly resistive layer to reduce leakage current through the dielectric stack. The use of molecular beam epitaxy allows for the control and uniformity of the oxide layers along the growth direction and deposition conditions were optimized for oxide surface morphology and interface quality. A midgap interface state density for the high-kappa stack on GaAs of congruent to 2 x 10(11) cm(-2) eV(-1) and a dielectric constant Of kappa congruent to 20 are determined using electrical measurements. Enhancement-mode n-channel MOSFETs with a gate length of 1 mu m and a source-drain spacing of 3 mu m show a threshold voltage, saturation current, transconductance, and on-resistance of 0.11 V, 380 mA mm(-1), 250 mS mm(-1), and 4.5 Omega mm, respectively. (c) 2006 Elsevier B.V. All rights reserved.