The dielectric properties of MgO-Ta2O5 continuous composition spread (CCS) thin films were investigated. The MgO-Ta2O5 CCS thin films were deposited on Pt/Ti/SiO2/Si substrates by off-Axis RF magnetron sputtering system, and then the films were annealed at 350 degrees C with rapid thermal annealing system in vacuum. The dielectric constant and loss of MgO-Ta2O5 CCS thin films were plotted via 1500 micron-step measuring. The specific point of Ta2O5-MgO CCS thin film (post annealed at 350 degrees C) showing superior dielectric properties of high dielectric constant (k similar to 28) and low dielectric loss (tan delta < 0.004) at 1 MHz were found in the area of 3-5 mm apart from Ta2O5 side on the substrate. The cation's composition of thin film was Mg:Ta = 0.4:2 at%. (C) 2011 Elsevier B. V. All rights reserved.