Abstract: The thermal stability and the resistance to oxygen diffusion of（HfO₂）_x（Al₂O₃）_y（NiO）_1-x-y gate dielectrics deposited on p-type Si（100） substrate by laser molecular beam epitaxy technique（LMBE） have been investigated.X-ray diffraction（XRD） results indicate that the crystallization temperature significantly increases with Ni and Al added into the HfO₂ film.Atomic force microscopy（AFM） testing shows that the surface of these films after annealing in N₂ is continuous and flat at the atomic level with no pinhole observed.No silicate interfacial layer is found in the high-resolution cross-section transmission electron microscope（HRTEM） images of the（HfO₂）x（Al₂O₃）y（NiO）1-x-y films after 900℃ annealing in N₂.It is indicated that the interposed layer of Ni-Al-O between the oxide film and the Si substrate enables to avoid the formation of low-κ silicate interfacial layer,which is favorable for MOS to further downscale.