Ultra thin tungsten nitride film growth by chemical vapor deposition was explored on thermally grown SiO2. In situ X-ray photoelectron spectroscopy (XPS) and low energy ion scattering spectroscopy are used to establish the minimum equivalent film thickness needed to fully cover the dielectric substrate. Three-dimensional tungsten nitride growth is suggested in the initial nucleation stage by the non-linear relationship of substrate ion scattering features and the XPS-based nitride film thickness. Both higher deposition temperature and predeposition of a plasma-enhanced chemical vapor deposited tungsten nitride seed layer significantly lowers the film thickness needed to fully cover the substrate. (C) 2003 Elsevier B.V. All rights reserved.