Residual-stress evolution in sputtered encapsulated ZnO/Ag/ZnO stack has been studied in-situ by synchrotron x-ray diffraction when heat treated. The ZnO/Ag/ZnO stack encapsulated into Si(3)N(4) layers and deposited on (001) Si substrates was thermally heated from 25 degrees C to 600 degrees C and cooled down to 25 degrees C. X-ray diffraction 2D patterns captured continuously during the heat treatment allowed monitoring the diffraction peak shifts of both Ag (15 nm thick) and ZnO (10 nm and 50 nm thick) sublayers. Due to the mismatch between the coefficients of thermal expansion, the silicon substrate induced compressive thermal stresses in the films during heating. We first observed a linear increase of the compressive stress state in both Ag and ZnO films and then a more complex elastic-stress evolution starts to operate from about 100 degrees C for Ag and about 250 degrees C for ZnO. Thermal contraction upon cooling seems to dominate so that the initial compressive film stresses relax by about 300 and 700 MPa after thermal treatment for ZnO and Ag, respectively. The overall behavior is discussed in terms of structural changes induced by the heat treatment. (C) 2011 Elsevier B.V. All rights reserved.