Abstract The crystalline structure and surface morphology of Dy x O y dielectric films grown on Si substrates were studied by grazing incidence diffraction and absorption with use of synchrotron radiation and by atomic force microscopy. The crystalline structure and the roughness of Dy x O y films were found to be strongly dependent on the deposition rate. The dielectric-silicon interface depends on the type of gas used in the annealing process. Moreover, results from the near edge X-ray absorption studies, have revealed that none of the examined films has a stoichiometry close to the Dy 2O 3. The level of stoichiometry is determined by the technological conditions. Nevertheless, MOS structures with Dy x O y films (EOT ∼ 23 Å) have shown a rather good Dy x O y -Si interface properties, which can be further improve by thermal annealing, and introducing of several additives, therefore Dy x O y films can be considered as suitable candidates for gate dielectric in MOS devices.