Thin films of the aluminum oxide (Al2O3)-yttrium oxide (Y2O3) system including Al2O3, Y2O3, and mixed Al2O3-Y2O3 were prepared by radio-frequency magnetron sputtering using ceramic targets of Al2O3, Y2O3, and Al2O3-Y2O3 with different Y2O3/(Al2O3 +Y2O3) molar ratios. These films were deposited at different substrate temperatures. The low-Y2O3 composite films had growth rate insensitive to deposition temperature, while a decreased rate at high temperature for the rest of films. The growth rates ranged 0.13-0.35 mu m/h. Composition, growth morphology, dielectric properties, and electrical properties were investigated. The mixed-oxide films of the Al2O3-Y2O3 system had a varied dielectric constant of 8-13.5, a loss tangent of similar to 0.05, leakage current density of similar to 10(-6) A/cm(2) at 80 kV/cm, and varied breakdown strength of 2.2-4.8 MV/cm, depending upon the Y2O3 amount. Point defects in pure Y2O3 films are the reason for degraded dielectric performance. (c) 2005 Elsevier B.V. All rights reserved.