We have prepared Ba0.5Sr0.5TiO3 thin films on Si substrate without buffer layer. Deposition was carried out by off-axis rf magnetron sputtering method using Ba0.5Sr0.5TiO3 stoichiometric target. The substrate temperature was changed from 40$0^{circ}C$ to $700^{circ}C$ during deposition. As the substrate temperature increased, relative intensity of (110) peak increased up to $600^{circ}C$, however preferred orientation changed from (110) to (h00) beyond $650^{circ}C$ of substrate temperature. Deposited films showed microstructures with fine grains whose diameters are less than 100 nm, and columnar structure was observed in the cross-sectional SEM micrograph. AES depth profile showed no significant diffusion at the interfacial reaction area. The effective dielectric constant of films showed maximum value at $600^{circ}C$, and the leakage current increased with increasing substrate temperature, which may be ascribed to the crystallization of amorphous phases at grain boundary.