Quaternary Ba0.5Sr0.5TiO3 (BSTO) thin films were deposited on (100) Si by pulsed laser deposition with conductive SrRuO3 (SRO) bottom electrodes. The growth of highly (001)-oriented SRO film on (100) Si was accomplished by using a bilayer buffer CeO2 and yttria-stabilized zirconia (YSZ). The BSTO films deposited on SRO on Si using such a buffer system were well aligned in the plane with respect to the major axes of the substrate confirmed by X-ray diffraction. The crystalline nature of the BSTO films on Si was further illustrated by Rutherford backscattering spectrometry and cross-sectional transmission electron microscopy. The BSTO thin films exhibited a dielectric constant above 340 at 10 kHz tested from a capacitor configuration of Au/BSTO/SRO.