The structure and thermal stability of ZrO2 films grown on Si (1 0 0) substrates by metalorganic chemical vapor deposition have been studied by high-resolution transmission electron microscopy, selected area electron diffraction and X-ray energy dispersive spectroscopy. As-deposited films consist of tetragonal ZrO2 nanocrystallites and an amorphous Zr silicate interfacial layer. After annealing at 850degreesC, some monoclinic phase is formed, and the grain size is increased. Annealing a similar to6 nm thick film at 850degreesC in O-2 revealed that the growth of the interfacial layer is at the expense of the ZrO2 layer. In a 3.0 nm thick Zr silicate interfacial layer, there is a 0.9 nm Zr-free SiO2 region right above the Si substrate. These observations suggest that oxygen reacted with the Si substrate to grow SiO2, and SiO2 reacted with ZrO2 to form a Zr silicate interfacial layer during the deposition and annealing. Oxygen diffusion through the tetragonal ZrO2 phase was found to be relatively easier than through the monoclinic phase. (C) 2003 Elsevier Science B.V. All rights reserved.