Interfacial reactions and electrical properties of RF sputter deposited HfTaO x high-k gate dielectric films on Si 1−x Ge x (x=19%) are investigated. X-ray photoelectron spectroscopic analyses indicate an interfacial layer containing GeO x , Hf silicate, SiO x (layer of Hf–Si–Ge–O) formation during deposition of HfTaO x . No evidence of Ta-silicate or Ta incorporation was found at the interface. The crystallization temperature of HfTaO x film is found to increase significantly after annealing beyond 500°C (for 5min) along with the incorporation of Ta. HfTaO x films (with 18% Ta) remain amorphous up to about 500°C anneal. Electrical characterization of post deposition annealed (in oxygen at 600°C) samples showed; capacitance equivalent thickness of ~4.3–5.7nm, hysteresis of 0.5–0.8V, and interface state density=1.2–3.8×10 12 cm −2 eV −1 . The valence and conduction band offsets were determined from X-ray photoelectron spectroscopy spectra after careful analyses of the experimental data and removal of binding energy shift induced by differential charging phenomena occurring during X-ray photoelectron spectroscopic measurements. The valence and conduction band offsets were found to be 2.45±0.05 and 2.31±0.05eV, respectively, and a band gap of 5.8±05eV was found for annealed samples.