Disclosed is a method for forming metal oxide dielectric layers, more particularly HfO.sub.2 dielectric layers, using an atomic layer deposition (ALD) method in which a series of thin intermediate layers are formed and treated with one or more oxidizers and nitrogents before the next intermediate layer is formed on the substrate. The intermediate oxidation treatments reduce the number of organic contaminants incorporated into the metal oxide layer from the organometallic precursors to produce a dielectric layer having improved current leakage characteristics. The dielectric layers formed in this manner remain susceptible to crystallization if exposed to temperatures much above 550.degree. C., so subsequent semiconductor manufacturing processes should be modified or eliminated to avoid such temperatures or limit the duration at such temperatures to maintain the performance of the dielectric materials.