We report the use of chemical vapor deposition (CVD) for tungsten silicide (WSi2) gate deposition on an Al2O3/GaAs substrate for the realization of III-V metal-oxide-semiconductor capacitor stacks. The as-deposited capacitor shows smooth and abrupt interfaces and exhibits good capacitance-voltage (C-V) characteristics with low frequency dispersion at flatband voltage and accumulation. A lower dielectric constant for Al2O3 (Keff similar to 6.4) is reported due to fluorine incorporation from the precursor during the CVD process. The work function of the as-deposited WSi2 metal gate is determined to be similar to 4.2 eV and increases to similar to 4.4 eV after thermal annealing at 600 degrees C as observed from the C-V measurement due to hexagonal-tetragonal WSi2 phase transformation. (C) 2010 The Electrochemical Society. [DOI: 10.1149/1.3460300] All rights reserved.