In this article, ytterbium (Yb) incorporation into NiGe is proposed to improve the thermal stability of Ni germanide for high-performance Ge metal-oxide-semiconductor field-effect transistors (Ge MOSFETs). The Yb/Ni/TiN structure shows suppression of NiGe agglomeration and better surface morphology than the Ni/TiN structure after a postgermanidation annealing of up to 550 degrees C for 30 min. It is notable that Yb atoms distribute uniformly at the top region of NiGe. NiGe agglomeration was retarded by Yb incorporation, and the thermal stability of NiGe was therefore improved.