Thin films of HfO2 have been deposited by liquid-injection metal–organic (MO)CVD using two nitrogen-containing precursors [Hf(NMe2)4] and [Hf(ONEt2)4]. The [Hf(NMe2)4] precursor deposits oxide at lower growth temperatures and over a wider temperature range than [Hf(ONEt2)4]. Varying levels of residual carbon and nitrogen were detected in the films grown from each precursor. Analysis by X-ray diffraction (XRD) indicates that films grown from both precursors exist predominantly in the thermodynamically stable monoclinic phase. Scanning electron microscopy (SEM) shows that the morphology of the HfO2 films from each precursor is markedly different, with films deposited from [Hf(NMe2)4] having a well-defined columnar crystalline structure, whereas films grown from [Hf(ONEt2)4] are smoother with little evidence of columnar structure. Full crystal structure data for [Hf(NMe2)4] are given, and the dielectric properties of [Al/HfO2/n-Si(100)] MOS capacitors, fabricated using each precursor, are also reported.