This study examined the effects of postdeposition annealing (PDA) on the electrical characteristics of atomic layer deposited ZrO2 and HfO2 films using similar precursors and process conditions. After PDA at 600 degrees C, the insulating properties of ZrO2 improved but those of HfO2 deteriorated. The improved insulating properties of ZrO2 were attributed to the negligible increase in the interfacial layer thickness and an amorphous to tetragonal phase transformation. In addition, the degraded insulating properties of HfO2 after PDA at high temperatures were attributed to an abrupt increase in the interfacial layer thickness and the generation of conducting paths through the grain boundaries. (C) 2011 The Electrochemical Society. [DOI: 10.1149/1.3551460] All rights reserved.