Ba0.5Sr0.5TiO3 (BST) thin films were deposited on copper foils via sol-gel method with La2O3 as a buffer layer. The films were processed in almost inert atmosphere so that the substrate oxidation was avoided while allowing the perovskite film phase to crystallize. The existence of a La2O3 buffer layer between the BST thin film and Cu foil improved the dielectric constant and reduced the leakage current density of the BST thin film. Meanwhile, the BST thin film exhibited ferroelectric character at room temperature, which was contrast to the para-electric behavior of the film without the buffer layer. Effects of La2O3 buffer layer on the crystallizability and microstructure of BST thin films were also investigated. (C) 2009 Elsevier B.V. All rights reserved.