Y2O3 thin film was deposited by atomic layer deposition (ALD) with a new precursor yttrium tris(N,N‘-diisopropylacetamidinate), Y(iPr2amd)3, and water. The precursor was thermally stable and volatile and had high reactivity with water. The growth rate of Y2O3 films was 0.8 Å/cycle over a wide temperature range (150−280 °C). The films were very pure (C, N < 0.5 at. %) and had a refractive index of 1.8. The films were smooth and had a cubic polycrystalline structure. High quality films were also deposited in 40:1 aspect ratio profiled substrates. Y2O3 films adsorbed water after air exposure because Rutherford backscattering spectroscopy (RBS) and X-ray photoelectron spectroscopy (XPS) showed an increased oxygen ratio (O/Y > 1.5) and −OH bonds in air-exposed films. A relatively high permittivity (∼12), a low leakage current density (<10-7 cm2 at 2 MV/cm) and high electrical breakdown field (∼5 MV/cm) were measured for capacitors prepared from Al2O3 (10 Å)/Y2O3/n-Si structures. Uncapped Y2O3 films showed flatband voltage shifts of 1 V and increased leakage current prior to annealing. ALD Y2O3 is a promising dielectric for advanced electronic applications in nanoscale devices.