We have investigated changes of the structure for HfSiO and HfSiON film with different annealing temperature by photoelectron spectroscopy. Core level photoelectron spectra have revealed the mechanism of metallization reaction at the bottom interface between the HfSiO(N) film and Si substrate under vacuum annealing. Silicidation action occurs by annealing at 850 and 900 degrees C for HfSiO and HfSiON film, respectively, indicating the incorporation of nitrogen enhances the thermal stability. By annealing at 900 degrees C, metallization reaction is rapidly promoted for the HfSiO film. For HfSiON film, Hf-nitride clusters or Hf-nitride layer and metal-silicide are formed at the bottom and upper interface, respectively, upon annealing at 950 degrees C. (C) 2011 Elsevier B.V. All rights reserved.