It is widely reported that a significant amount of germanium is incorporated in HfO2 gate dielectric during the formation of high-kappa gate stack on germanium substrate. In this paper, the dependences of germanium incorporation in HfO2 on dielectric deposition method, annealing temperature, and annealing ambient were extensively studied by physical methods such as time-of-flight secondary ion mass spectroscopy. The results indicate that the high thermal budget of processes, including deposition and annealing, is the most critical factor to the Ge incorporation. The Ge incorporation in HfO2 is identified by two mechanisms: Ge atoms out-diffusion from substrate and gaseous GeO diffusion downward into HfO2 via airborne transportation in the chamber. (c) 2006 The Electrochemical Society.