Silicide formation in thin cobalt/poly-Si layers capped with Ti during annealing in the temperature range between 420 and 510degreesC was investigated by time-resolved sheet resistance measurements. We found that CoSi2 nucleation is a fast process while Co diffusion through CoSi2 grain boundaries is a slow process. Simulations of the resistance curves vs. time have shown that the pre-exponential factor of cobalt diffusivity is reduced by the presence of Ti contamination at the CoSi2 grain boundaries, as it was shown by energy-filtered transmission electron microscopy analyses, whilst the activation energy does not change with respect to a reference. (C) 2004 The Electrochemical Society.