In this study, we report the effect of process conditions on the crystallinity and energy band structure of atomic layer deposition (ALD) ZrO2 films deposited, using tris(dimethylamino) cyclopentadienyl zirconium as a precursor and ozone as a reactant. ZrO2 films exhibited systematic changes in phase and energy band gap as a function of the ozone concentration. The crystal phase was transformed from the monoclinic phase to a tetragonal phase in the presence of higher ozone concentrations. In addition, spectroscopic ellipsometry measurements showed that the optical band gap and oxygen vacancy defects decreased with increasing ozone concentration. The valence band maximum also shifted closer to the Fermi energy level with increasing ozone concentration. The change in electronic structure driven by a high concentration of ozone led to reduced leakage current density and a high dielectric constant in the ZrO2-based metal-insulator-metal capacitors. These improvements were not observed for depositions performed using conventional ZrO2 ALD with oxygen and water reactants. (C) 2016 Published by Elsevier B.V.