Radio frequency magnetron sputter deposition of Pb3MgTa2O9 (PMT) thin films on n-type (1 0 0) Si wafers is investigated in a low pressure ambient of Ar and Or. The process is optimized with process variables including rf power density, substrate temperature, ambient pressure, Or mass now and target composition. The properties of the films including refractive index, morphology, composition, crystallinity, microstructure and electrical proper ties are characterized as functions of the process parameters and correlated. The films as grown at 300 degreesC are amorphous and become polycrystalline upon annealing at 600 degreesC and above. The dielectric constants are between 29 and 129. The leakage current densities are below 1 x 10(-7) A cm(-2) at Ix 10(6) V cm(-1) and further improved after annealing.