The nucleation stage toward CoSi2 with average island size of about 4 nm and uniform island size distribution is obtained from a TiN/Co/ Ti/Co/SiOx/Si multilayer with the SiOx as a mediated layer by annealing at 460 degrees C for 240 s followed by 600 degrees C 240 s. It is found that Ti capping layer can enhance Co diffusion into the Si substrate at higher temperature (600 degrees C 240 s) annealing, which results in larger nucleus size (average grain size about 12 nm) but nonuniform nucleus size distribution. However, two-step annealing for 460 degrees C 240 s followed by 600 degrees C 240 s results in a smaller average nucleus size with better nucleus size distribution. The mechanism responsible for the discrepancy is discussed in the paper. (c) 2005 Elsevier B.V. All rights reserved.