The thermal stabilities of the Ni-silicide and Ni-germanide systems were compared, and that of the Ni0.9Ta0.1/Ge alloy system was also studied. Although the NiSi film had a stable low sheet resistance (R-s) in the formation temperature range from 300 to 650 degrees C, NiGe exhibited an abrupt increase of R-s from 500 degrees C due to the severe agglomeration. The doping of the Ni film with Ta slightly improved the thermal stability of NiGe due to the formation of a Ta-rich layer on top of NiGe and subsequent reduction of the surface-free energy of NiGe with outside ambient. During the additional thermal annealing after NiGe formation, the germanide films formed from Ni-Ta alloy also exhibited slightly improved thermal stability characteristics as compared to the pure Ni-germanide system. (C) 2007 The Electrochemical Society.