The properties for Ru/Ta and Ru/TaN bi-layer on Si substrate were investigated. The Ru, Ta and TaN films were deposited by ion beam sputtering technology and were annealed at temperatures ranging from 300 degrees C to 900 degrees C in high purity N-2 ambient. The phase formation, microstructure evolution and thermal stability for the Ru/Ta/Si and Ru/TaN/Si structures were investigated. Results show that adding the Ta or TaN layer between Ru and Si delays the reaction of Ru with Si. The Ru/TaN bi-layer is more stable on Si and shows better diffision barrier property than the Ru/Ta bi-layer. (c) 2005 Elsevier B.V All rights reserved.