We report the room temperature growth of hafnium silicate by ultra-violet/ozone oxidation of hafnium silicide. Hafnium silicide was deposited by magnetron sputtering on hydrogen terminated (100) Si. The film was then exposed to UV radiation while in an O-2 ambient. Hafnium silicate films are obtained with no detectable SiOx interfacial layer as characterized by X-ray photoelectron spectroscopy and high-resolution transmission electron microscopy.