Electrical and structural properties of strontium titanate (SrTiO3) thin films deposited on Si and GaAs substrates by a conventional radio frequency-magnetron sputtering technique at different oxygen (O-2) partial pressures and substrate temperatures have been reported. Dielectric constant of the as-deposited samples increases with the substrate temperature as well as the O-2 partial pressure. However, it shows a decreasing trend at higher O-2 partial pressure values. When the samples were annealed for 1 h at temperatures above 500 degrees C the dielectric constant value of the SrTiO3 (STO) films increased by five times and a maximum value of 147 was obtained. The increase in the dielectric constant value is reflected in x-ray diffraction measurements with the development of high intensity lines corresponding to STO phase. The thickness dependence of the dielectric constant is also reported. Thin film STO capacitors fabricated with Pt as top and bottom electrodes showed low leakage current densities and a high breakdown voltage of 855 kV/cm suggesting the possibility of considering these capacitors for integration with devices.