Atomic layer deposition (ALD) is considered an enabling technique for the deposition of dielectrics on sensitive surfaces such as germanium. Proper control of the interfacial layer between Ge and the high-kappa layer has been shown to be crucial for obtaining good performance of Ge-based metal-oxide-semiconductor devices. In this work, we compare O-3- and H2O-based ALD of HfO2 and Al2O3, and report on the thickness and electrical quality of GeO2 passivation layers. The thickness of the interfacial layer depends on the oxidant used and affects the interface state density. A small. degree of intermixing at the GeO2/high-kappa interface is observed for all ALD process conditions. The interface state density can be significantly reduced by annealing the Pt-gated capacitors in forming gas (H-2/N-2) at 300 degrees C. After annealing, the interface state density becomes almost independent of the thickness of the GeO2 passivation layer. (C) 2009 The Electrochemical Society. [DOI: 10.1149/1.3200902] All rights reserved.