As a conductive layer, sputter-deposited Al-Cu 1 at.% thin film was investigated, with particular focus on the effect of Cu precipitates and film strain on the electric conductivity. The 400-nm-thick film was deposited on Si wafer and heat-treated at 200 and 480 degreesC. Cu precipitation was investigated using electron microscopy and film strain using XRD. As a result of heat treatment, changes in the electric resistivity showed the same trend as the film strain. This study concluded that the trends in resistivity and film stress could be related to Cu precipitation to some extent. In other words, the resistivity changes depending on whether the precipitates are coherent with the Al matrix and on the distribution of the precipitates. (C) 2003 Elsevier Science B.V. All rights reserved.