In order to get more insight into the growth mechanism of polycrystalline silicon deposited by hot-wire chemical vapor deposition on Coming glass, spectroscopic and kinetic ellipsometry studies have been performed. Spectroscopic ellipsometry measurements have been performed on layers, deposited using different levels of hydrogen dilution. From this study, it followed that the crystallinity of the films becomes higher with higher hydrogen dilution. Kinetic ellipsometry measurements have been performed during the deposition of profiled layers, starting with a seed layer deposited at high hydrogen dilution. This study showed that by using a seed layer, highly crystalline layers could be deposited using a lower hydrogen dilution. Without the use of the seed layer, this lower hydrogen dilution yields amorphous silicon layers. (C) 2003 Published by Elsevier Science B.V.