Gallium arsenide metal oxide semiconductor field effect transistors (GaAs MOSFETs) were successfully demonstrated with a specially formulated gallium oxide/gadolinium oxide as the gate dielectric material. For the fabrication of MOSFETs, dry and wet etching of Ga2O3 (Gd2O3) has been investigated. The content of Gd2O3 in the oxide is dependent on the deposition conditions and can vary from 10 to approximately 44%. The etching characteristics of the Ga2O3(Gd2O3) film is affected by the content of Gd. An HCl based wet etch shows smooth surface morphologies of Ga2O3(Gd2O3) and would not attack the underlying GaAs. She etch rate of Ga2O3(Gd2O3) is linearly proportional to the concentration of HCl. Furthermore, the etching was determined to be a reaction-limited process, For dry etching, the rates for both SF6 and BCl3 based discharges are very low due to the incorporation of Gd and the lack of etch selectivity to the GaAs substrate.