(Ba0.5Sr0.5)TiO3 (BST) films were deposited on (111)Pt/TiO2/SiO2/Al2O3 substrates by rf sputtering. By inserting a thin layer of SrRuO3 in between BST film and (111)Pt electrode, the BST films grew fully (111)-oriented without any other orientations. In addition, it enables us to reduce the growth temperature of BST films while keeping the dielectric constant and tunability as high as those of BST films directly deposited on Pt at higher temperatures. The dielectric loss of the films on SrRuO3-top substrates was comparable to that on Pt-top substrates for the same level of dielectric constant. The results suggest that the SrRuO3 thin layer on (111)Pt electrode is an effective approach to growing highly crystalline BST films with (111) orientation at lower deposition temperatures.