In this work, we address the effect of C+ ion implantation on the formation of nickel-germanosilicide NiSi0.8Ge0.2 on relaxed Si0.8Ge0.2 layers. The layer morphology and sheet resistance are investigated as a function of the C+ implantation dose and annealing temperature. The presence of C atoms increases the thermal stability of NiSiGe by about 200 degrees C. We demonstrate that the carbon atoms retard the Ni germanosilicidation rate, stabilize the NiSiGe phase. Due to C segregation at grain boundaries and interface during annealing, the NiSi0.8Ge0.2/Si0.8Ge0.2 interface is smoothed. (C) 2011 The Electrochemical Society. [DOI: 10.1149/1.3578387] All rights reserved.