In this work, Cu-Al alloy thin films with lower values of electrical resistivity than that of an Al-free Cu thin film were produced by cyclic metalorganic chemical vapor deposition (MOCVD), followed by thermal annealing of the Cu/Al multilayer formed, with controlled Cu and Al precursor delivery times. The Ru-coated SiO2 trench with the opening width of 50 nm and aspect ratio of 1:6.7 could be completely filled by the Cu-Al alloy. The Ru/SiO2 trench, filled conformally and voidlessly by the Cu-Al (0.7 at.%) alloy, showed no presence of intermetallic compounds. (C) 2012 Elsevier Ltd. All rights reserved.