BST thin films have been investigated as potential candidates for use in frequency agile microwave circuit devices. Stoichiometric (Ba1-xSrx)TiO3 (BST) thin films have been prepared on Pt/SiO2/Si substrates using sol- gel method. The BST films were characterized by X-ray fluorescence (XRF) spectroscopy analysis, X-ray diffraction (XRD), scanning, electron microscope (SEM) and electrical measurements. The relationships of processing parameters, microstructures, and dielectric properties are discussed. The results show that the films exhibit pure perovskite phase through rapid thermal anneal at 700 degrees C and their grain sizes are about 20-40 nm. The dielectric constants of BST5, BST10, BST15 and BST20 are 323, 355, 382 and 405, respectively, at 80 kHz. (C) 2005 Elsevier Ltd. All rights reserved.