The growth of (Ba_xSr_1-x)TiO₃, BST, thin films on Pt-(111) surfaces was investigated within a wide parameter field. The deposition temperature was varied between 560°C and 650°C, which yields films with microstructures ranging from randomly oriented polycrystalline to perfectly (100)-textured columnar structures. Starting with (Ba_0.7Sr_0.3)TiO₃ the Group-II/Ti content was varied from 0.9 to 1.1 and drastic changes in the surface morphology were observed. As the dielectric permittivity and the leakage current depend strongly on the film thickness, the thickness was varied between 5 and 100 nm and the data were analyzed using the phenomenological dead layer model. The relations between the stoichiometry dependence of the microstructural and electrical properties are emphasized.