The electrical properties of (Ba, Sr)TiO3/(Ba, Sr)RuO3 capacitors as a function of the (Ba, Sr)TiO3 film thickness were investigated. It was found that the electrical properties degraded, as the thickness of the dielectric film decreased. As the thickness of the (Ba, Sr)TiO3 films varied from 30 to 200 nm, the dielectric constants and T-eq were 122, 0.96 and 515, 1.5 nm, respectively. The corresponding leakage current densities were 2.7 x 10(-5) A/cm(2) at 30 nn and 2.14 x 10(-8) A/cm(2) at a 200 nm (Ba, Sr)TiO3 thickness. However, after postannealing at 700 degrees C, the dielectric constants and T-eq of (Ba, Sr)Tio(3)/(Ba, Sr)RuO3 capacitors with a 30 nm (Ba, Sr)TiO3 thickness were 230 and 0.51 in N-2 and 200 and 0.59 nm in O-2, respectively, and the leakage current levels were 1.67 x 10(-6) A/cm(2) in N-2 and 1.64 x 10(-7) in O-2 Electrical properties of postannealed specimens improved when compared to those of as-deposited (Ba,Sr)TiO3/(Ba, Sr)RuO3 capacitors. The dielectric constant and leakage current density annealed in N-2 is a little bit higher than those of the film annealed in an O-2 atmosphere. These differences appear to be attributable to an increased surface roughness and grain boundary defects. Electrical properties such as the leakage current and the relative dielectric constant, are closely related to the surface morphology, in particular, the grain size and grain boundary of the films.