(Ba0.5Sr0.5)TiO3 (BST) thin films were deposited on Si and plantinized Si substrates using sol-gel method with rapid thermal annealing (RTA), The films were characterized by inductive coupled plasma (ICP) analysis, X-ray diffraction (XRD), atomic force microscope (AFM), scanning electron microscope (SEM) and electrical measurements. BST get well crystallized after RTA at 700 degrees C for 5 min. Grain size, grain height, and thus, surface roughness and film density increase with the increase of annealing time. SEM cross-section results clearly demonstrate a better BST/substrate interface compared with conventional annealing. The dielectric constant and loss tangent of BST films at 10 kHz are 435 and 0.069, respectively. This good dielectric property is believed to arise from the better BST/substrate interface.