This paper discusses thermo-mechanical behavior of plasma-enhanced chemical vapor deposited oxide films during and after post-deposition thermal cycling and annealing. A series of thermal cycling experiments were conducted with various types of oxide and nitride films to elucidate the control mechanism of intrinsic stress generation and to develop engineering solutions for improving reliability of microelectromechanical system fabrication processes. Tensile intrinsic stress generation was observed during thermal cycling and the depletion of hydrogen and the shrinkage of micro voids existing in the oxide films was postulated as a major control mechanism for the stress generation and was modeled by an energy-based formulation. Subsequent experiments indicated that annealing at high temperature could reduce this intrinsic tensile stress. Both stress generation and relaxation were modeled to guide the development of engineering solutions to maintain structural integrity and improve fabrication performance. (C) 2003 Elsevier Science B.V. All rights reserved.