We report a novel chemical vapor deposition (CVD) process for epitaxial growth of Ge film on GaAs substrate. The resultant layer exhibits device level quality, as shown by high-resolution transmission electron microscopy (HRTEM), Raman spectroscopy, high-resolution X-ray diffraction (HRXRD). In addition, atomic force microscopy (AFM) scanning indicates low RMS surface roughness of 5 Å. Secondary ion mass spectrometry (SIMS) reveals negligible out-diffusion of Ga and As into the Ge epilayer. By employing silane passivation, Ge p-MOSFET with TaN/HfO2 gate stack was fabricated on Ge/GaAs heterostructure for the first time, showing excellent output and pinch-off characteristics. A GaAs channel n-MOSFET was also fabricated, using similar SiH4 treatment during gate stack formation. These results reveal a potential solution to integrate Ge p-channel and GaAs n-channel MOSFET for advanced CMOS applications.