Among the widespread range of applications in which ZrO2 thin films are of interest, they are receiving a peculiar consideration as candidate replacement material in innovative microelectronic devices, such as non volatile memories. In this work, we deposited ZrO2 films on Si (100) substrates by atomic layer deposition at 300 degrees C from (MeCp)(2)ZrMe(OMe) as Zr precursor and using, H2O or O-3 as oxygen source. After deposition films were subjected to rapid thermal annealing at 800 degrees C for 60 s in N-2. Film thickness is calculated from X-ray reflectivity to be in the 5-60 nm range. Grazing incidence X-ray diffraction reveals that the film crystallographic phase is highly influenced by the oxidizing agent used during the deposition process. While the use of H2O gives films consisting of mixed phases, the monoclinic phase is almost absent in films deposited employing O-3, which stabilize in the ZrO2 cubic/tetragonal phases. Upon annealing, the films retain their crystallographic structure, despite a marginal increment of the monoclinic phase. Time of flight secondary ion mass spectrometry depth profiles evidence film uniformity and thermal stability. The evolution of electrical properties of ZrO2 films is discussed as a function of oxygen precursor and thermal treatment. The measured dielectric constant values after 800 degrees C annealing are kappa similar to 24 and kappa similar to 30 in the films deposited using H2O or O-3 respectively, in agreement with the different crystallographic phases in the ZrO2 films. (C) 2011 The Electrochemical Society. [DOI: 10.1149/1.3625254] All rights reserved.