Abstract: Al₂O₃/NbAlO/Al₂O₃ dielectric stacks were grown on strained Si_0.8Ge_0.2 substrate and annealed 500℃.high resolution transmission electron microscopy（HRTEM） indicated the films were crystallized,synchrotron radiation X-ray reflectivity measurements（XRR） and x-ray diffraction（XRD） measurements showed that the super-lattice（SL） structure appeared with a period of 2.5nm and an interfacial layer（IL）of 0.5nm existed.X-ray photoelectron spectra（XPS） suggested that the main composition of IL was SiOx,and the valence-band offset between the dielectric film and SiGe interface was 2.9eV.The electrical measurements indicated that the equivalent oxide thickness and the dielectric constant were 1.8nm and 19 respectively.