Trilayers of SnO2/Ag/SnO2 deposited on oxidized Si (100) substrates at room temperature become unstable after annealing at 100 degrees C and 200 degrees C, exhibiting five phenomena - formation of internal Ag hillocks, cracking of the top SnO2 layer above internal Ag hillocks, penetration of Ag/Ag grain boundaries by SnO2 leading to grain pinch-off, formation of Ag whiskers and islands on the free surface of the SnO2 through the cracked top layer, and void formation in the Ag layer. The possible driving forces and evolution path for the observed instabilities resulting from thermal expansion mismatch stresses and the reduction in interfacial energy are discussed. (C) 2012 Elsevier B. V. All rights reserved.