A high density of Pd catalytic particles is an important factor for obtaining a uniform and continuous Ag seed layer in electroless plating. Adequate surface pretreatment is critical for the formation of such a Pd catalytic particle population. In this study, electroless plating of Ag thin films on TiN substrates was performed using Sn sensitization and Pd activation as pretreatment methods. Sn surface sensitization improves surface wetting and aids in the formation of a Pd catalytic layer in surface-oxidative Pd activation. The Pd activation supported by Sn sensitization also accelerated the formation of a continuous thin Ag film. Furthermore, a thin Ag seed layer deposited on a patterned structure showed excellent conformality. (C) 2008 The Electrochemical Society.