The MOS technologies are making rapid progress in their performance and scale, and the EOT (Equivalent Oxide Thickness) will be needed to decrease to less than 1 nm at the 65 nm generation. Since silicon oxide gate dielectric materials that are extended with use of nitrization have nearly reached their leakage limits, the high-k gate dielectric material is now required. The series of materials consisting of hafnium are the most promising ones in high-k dielectric. It is well known that impurities in the high-k gate dielectric films influence the performance of the MOS devises. Therefore, it is very important to control the amount of impurities. Although SIMS is a very powerful tool for depth profiling, it is very difficult to do quantification for correct distribution of impurity in these materials because of their variable composition. We discuss the problems such as change in sensitivity and the sputtering rate due to the variation in the composition, and describe how we have made an effort for those challenges.