Recently, the high-k materials (Al2O3, Ta2O5, HfO2, ZrO2,...,etc.), which are alternative dielectrics to silicon dioxide for memory and logic devices, come into notice. We have applied SIMS to the characterization of the ultra-thin HfO2 films. SIMS with low energy primary ion has proven to be a beneficial technique to see depth profiles of impurities and their behaviors due to annealing. As for Si substrate without native oxide, Si diffusion as well as the formation of amorphous HfxSi1-xOy layer at HfO2/Si interface seem to occur during growth of HfO2 film, which has been confirmed by SIMS and other analytical techniques. Furthermore, it is found that ion yield of carbon in HfO2 is larger than that in SiO2 by more than two orders of magnitude. (C) 2002 Elsevier Science B.V. All rights reserved.