Thin HfO₂ films have been deposited on silicon via atomic layer deposition using anhydrous hafnium nitrate [Hf(NO₃)₄]. Properties of these films have been investigated using x-ray diffraction, x-ray reflectivity, spectroscopic ellipsometry, atomic force microscopy, x-ray photoelectron spectroscopy, and capacitance versus voltage measurements. Smooth and uniform initiation of film growth has been detected on H-terminated silicon surfaces. As-deposited films were amorphous, oxygen rich, and contained residual NO₃ and NO₂ moieties from the nitrate precursor. Residual nitrates were desorbed by anneals >400 °C, however, the films remained oxygen rich. Crystallization of thin films (<10 nm) occurred at roughly 700 °C. For films less than ∼10 nm thick, the effective dielectric constant of the film and any interfacial layer (neglecting quantum effects) was found to be in the range of k∼10−11. From a plot of electrical thickness versus optical thickness, the dielectric constant of the HfO₂ layer was estimated to be k<sub>HfO₂</sub>-12-14. Leakage current was lower than that of SiO₂ films of comparable equivalent thickness. The lower than expected dielectric constant of the film stack is due in part to the presence of an interfacial layer (likely HfSiOₓ). Excess oxygen in the films may also play a role in the reduced dielectric constant of the HfO₂ layer.