Co/Si interface formation was monitored by a high-depth-resolution medium-energy ion scattering (MEIS) spectroscopy. High-purity 59Co thin films were deposited either at room temperature (RT) or at 400°C onto a clean Si(111) substrate using a very-low-energy (50 eV) ion beam deposition (IBD). In situ Auger electron spectroscopy (AES) was used to ascertain the atomic cleanliness of the silicon surface before growth. A post furnace anneal under N2 was performed in the range 300-700°C after Co deposition for the silicide formation. The structure and the effect of annealing on the electrical properties of these epitaxial film were investigated by MEIS and four-point probe measurements, respectively. Finally barrier heights were measured in this range of annealing temperature using the C-V technique.