Abstract: The composition and impurity concentration within thin films is strongly dependent on the deposition technique used in their preparation. In the present study we have prepared Tungsten silicide thin films by rf cathodic sputtering of a composite target WSi2.7 and studied the surface and composition of these samples using Auger Electron Spectrometry (AES) and X-ray Phototoelectron Spectrometry (XPS), the spectra show that the surfaces of the annealed thin films are covered by a thin layer of silicon dioxyde (SiO2), while the depth profile investigation gives evidence that oxygen is present at the silicide-substrate interface. We also measured the impurity profiles of our thin films using Secondary Ion Mass Spectrometry (SIMS), which is a more sensitive probe and found the following impurities, potassium, chlorine, fluorine, sodium, hydrogen. These impurities originate from the sputtering chamber and the sputtered target.