An oxide-based high-kappa gate dielectric stack for GaAs has been developed using molecular beam epitaxy. A template layer of Ga2O3, initially deposited on a GaAs(001) surface, serves to unpin 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. The 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 k congruent to 20 are determined using electrical measurements. Metal oxide semiconductor field effect transistor layer structures were produced by replacing the GaAs cap layer in a pseudomorphic high electron mobility transistor-type layer structure with the high-kappa gate dielectric stack. (c) 2006 American Vacuum Society.