Ru films were deposited on SiO2 and TiN substrates by low-pressure metallorganic chemical vapor deposition (MOCVD). To improve the low nucleation density of Ru on the two types of substrates and the resultant rough surface morphologies of the deposited films, the surface was pretreated with TiCl4 molecules using a repeated cyclic pulse and purge process. In this way, the nucleation density of Ru on the pretreated substrates was increased and continuous and smoother Ru films were obtained. X-ray photoelectron spectroscopy revealed that the improvement of the nucleation property is related to the change in the binding characteristics of the substrate surfaces. (C) 2007 The Electrochemical Society.