The thickness of HfO(2) and hafnium silicate Hf(x)Si(1-x)O(y) thin films with a range of compositions are investigated using three complementary analytical techniques. We compare results obtained from Medium Energy Ion Scattering spectroscopy, spectroellipsometry and high-resolution Transmission Electron Microscopy. Our results demonstrate that the thickness of the silicate layers decreases with the Hf content. (C) 2008 Published by Elsevier B.V.