The mechanical properties of thin film materials are known to be different from those of bulk materials, which are generally overlooked in practice. The difference in mechanical proper-ties can be misleading in the estimation of residual stress states in micro-gas sensors with multi-layer structures during manufacturing and in service. In this study the residual stress of each film layer in a micro-gas sensor was measured according to the five different sets of film stacking structure used for the sensor. The Pt thin film laver was found to have the highest tensile residual stress, which may affect the reliability of the micro-gas sensor. For,es in residual stress were measured as a function of processing variables and thermal cycling. In addition, the Pt layer the chang the residual stresses in the Pt layers caused by microstructural changes were also investigated.