Chemical bonding states and electrical characteristics of a nitrided high-k/Ge gate stack formed as a compositional transition layer at TiO2/Ge interface has been examined. Thin TiO2 have been deposited on p-type Ge (100) substrates by plasma enhanced CVD. The stoichiometry and chemical states are investigated by x-ray photoelectron spectroscopy. Depth profile XPS analyses revealed the formation of TiOxNy and GeOxNy after plasma nitridation. Peak decomposition technique was employed to identify the composition and the chemical states of the film. Stoichiometric TiO2 observed at the surface layer is found to reduce to Ti-suboxides after Ar+ ion sputtering. (C) 2011 The Electrochemical Society. [DOI: 10.1149/1.3545937] All rights reserved.