The structural, electrical properties of (Ba,Sr)TiO3[BSTO]/RuO2 thin films were controlled by the addition of amorphous BSTO layers between crystalline BSTO film and RuO2 substrate. We prepared BSTO films with double-layered structure, that is, amorphous layers deposited at 60 degrees C and crystalline films. Crystalline films were prepared at 550 degrees C on amorphous BSTO layers. The thickness of amorphous layers was varied from 0 to 170 nm. During the deposition of crystalline films, the crystallization of amorphous layers occurred and the structure was changed to circular while crystalline BSTO films showed columnar structure. Due to insufficient annealing effect, amorphous BSTO phase was observed when amorphous layers exceeded 30 nm. Amorphous BSTO layer could also prevent the formation of oxygen deficient region in RuO2 surface. Leakage current of total BSTO films decreased with increasing amorphous layer thickness due to structural modifications. Dielectric constant showed maximum value of 343 when amorphous layer thickness was 30 nm at which the improvement by grain growth and the degradation by amorphous phase were balanced.