We have investigated the structural changes in HfO 2 thin films upon Y and Al incorporation. The crystallinity of the films is examined by transmission electron diffraction. The local coordination symmetries of the Hf atoms in the films are revealed by the profile of the oxygen K-edge measured in the electron energy loss spectroscopy ͑EELS͒. The EEL spectra are then simulated using real-space multiple-scattering method. We found a good agreement between the simulated and the experimental EELS result of the pure HfO 2 . The Y incorporation indeed stabilized HfO 2 to a cubic structure. Nevertheless, it also contributed to possible lattice distortion and/or creation of complex defect states other than O vacancies, causing discrepancies between the experimental and the simulated results. As a comparison, the local symmetry of Hf is largely degraded upon the incorporation of Al, which not only amorphorized HfO 2 , but also introduced significantly amount of O vacancies in the film.