Direct electrodeposition of copper on osmium (Os) is described. Effective superfilling of submicrometer trenches by direct copper electrodeposition onto the osmium barrier layer is demonstrated. Surface modification of osmium prior to copper deposition as demonstrated herein, including electrochemical reduction in sulfuric acid and exposure to plating additives, presents an avenue for future process optimization. The work suggests further examination of Os as a diffusion barrier and/or adhesion layer for Damascene metallization. (c) 2005 The Electrochemical Society.