The thermal stability of magnetron sputtering deposited Mo/SiO 2 multilayered films was investigated by isothermal annealing, cross-sectional high resolution electron microscopy and Auger electron spectroscopy. No observable structural variation was visualized at the interface between Mo and SiO 2 after annealing at 400°C for 2 h. At 600°C, a small amount of as-deposited amorphous Mo began to crystallize at the top surface of the sample. Further increase in the annealing temperature resulted in the formation of large Mo crystalline grains in the film and destruction of the periodically distributed Mo/SiO 2 multilayer structure.