Ti/Co and Co/Ti bilayered systems were used for the formation of Co germanosilicide on polysilicon buffered poly-Si1 - xGex (x = 0.2, 0.3) gate stacks. In both cases, substantial Ge was found to segregate to the grain boundaries at the surface of the polycrystalline silicide (i.e., CoSiGe) films, resulting in a substantial degradation in the sheet resistance and a poor quality of the silicide films. It is shown that Ge is probably being expelled from the poly-SiGe grain and segregates to the grain boundaries during the annealing process, leading to the undesirable sheet resistance and poor film morphology observed from the Co germanosilicide films. (C) 2004 Elsevier B.V. All rights reserved.