A micro-electro-mechanical system (MEMs) technique, the bilayer cantilever beam method was used to examine the residual stress and the thermal expansion coefficient (alpha) of TaOxNy films by measuring the changes in radius of curvature. Residual stresses of all the TaOxNy films RF-deposited onto SiO2/Si (100) are compressive and varied from 2.5 to 12.5 MPa. The compressive stress is inversely proportional to the N-2/O-2 flow ratio except that appears at the flow ratio 0.5. However, the calculated a values, ranging from 7 X 10(-7) to 2 X 10(-5) degreesC(-1), increase proportionally with the N-2/O-2 flow ratio, except the value appears at the flow ratio 2. Comparing the a values of ZnS/SiO2 and Si3N4, films, the properties of TaOxNy films being optimizable by adjusting the N-2/O-2 flow ratios are obviously promising candidates in optical recording applications. Effects of other processing parameters on the a value and stress, such as the film thickness, RF power and reactive gas ratios during deposition, are also elucidated. Furthermore, a load-sensing nano-indentation method was used to examine the elastic property of the films. The obtained reduced elastic modulus E-r values of TaOxNy films are nearly constant (similar to 200 +/- 15 GPa) at the N-2/O-2 flow ratio from 0.25 to 2.