The aim of the present work is to investigate the outdiffusion of implanted boron from polycrystalline CoSi2overlayers into silicon. A detailed investigation is carried out on the secondary ion mass spectrometry (SIMS) quantification problems (matrix effects, interface roughness) applied to the determination of outdiffusion lengths and interface concentrations on mono and polycrystalline CoSi2overlayers. Comparative studies using spreading resistance profiling (SRP) are performed to assess the electrical performance of the outdiffused samples. The similarity in the behavior with polycrystalline silicon has led to the incorporation of outdiffusion from poly CoSi2into poly‐Si models.