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Thin films of nonstoichiometric titanium dioxide (TiO2) and zirconium oxide (ZrO2) chemically stabilized by incorporating stoichiometric oxides of Al2O3 and SiO2, respectively, were fabricated by rf magnetron sputtering. These films deposited from ceramic targets of TiO2, TiO2–10 vol %Al2O3, ZrO2, and ZrO2–10 vol %SiO2 were designated as TiO2, TiO2–10Al2O3, ZrO2, and ZrO2–10SiO2. The dielectric and electrical properties of as-deposited and annealed TiO2 and ZrO2 films varied with the processing conditions. The addition of Al2O3 to TiO2 and SiO2 to ZrO2 films had not only reduced the dielectric loss tangent (tan δ) and increased resistivity, but also retained the competitive dielectric constant (k). The dielectric properties of the TiO2–10Al2O3 and ZrO2–10SiO2 films became stable under different deposition temperatures and annealing temperatures. The TiO2–10Al2O3 films with k=62, tan δ=0.012, resistivity of 2.5×108 Ω cm, and breakdown field of 2.2 MV/cm were obtained. ZrO2–10SiO2 films with good k values of 20–25 and low tan δ values of 0.011–0.014 can be obtained under rf power of 150 W, while k=14.5–16.4 and tan δ=0.012–0.019 under 100 W can be obtained. The advantage of adding the stoichiometric oxides of Al2O3 and SiO2 is the reduction of oxygen vacancies through the strong affinity of Al3+ and Si4+ to capture more oxygen for nonstoichiometric oxides of TiO2 and ZrO2.