Insulating films consisting of thin layers of tantalum oxide and aluminum oxide were deposited using the atomic layer epitaxy technique at a temperature of 300 °C from metallic chlorides and H2O. The average film composition can be modified between pure aluminum oxide and pure tantalum oxide by varying the pulsing ratio. The effective refractive index is adjustable between 1.67 and 2.23 and the relative permittivity between 8.4 and 24. The leakage current of tantalum oxide is significantly reduced by thin interposed layers of aluminum oxide. These multilayers will potentially be useful, for example for applications in future memory integrated circuit and large-area display technologies.