HfO 2 thin films were prepared by reactive DC magnetron sputtering technique on (100) p-Si substrate. The effects of O 2 /Ar ratio, substrate temperature, sputtering power on the structural properties of HfO 2 grown films were studied by Spectroscopic Ellipsometer (SE), X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectrum, and X-ray photoelectron spectroscopy (XPS) depth profiling techniques. The results show that the formation of a SiO x suboxide layer at the HfO 2 /Si interface is unavoidable. The HfO 2 thickness and suboxide formation are highly affected by the growth parameters such as sputtering power, O 2 /Ar gas ratio during sputtering, and substrate temperature. XRD spectra show that the deposited films have (111) monoclinic phase of HfO 2 , which is also supported by FTIR spectra. XPS depth profiling spectra shows that highly reactive sputtered Hf atoms consume some of the oxygen atoms from the underlying SiO 2 to form HfO 2 , leaving Si-Si bonds behind.