The effect of formation temperature of epitaxial CoSi2 in the Co/Ti/Si system on electrical characteristics of a p+n junction diode has been investigated. When the silicide formation temperature was 800 °C, a very low reverse leakage current density of 11 nA/cm2 at a bias of -5 V was obtained. However, when the temperature was 900 °C, the reverse leakage current was increased by more than three orders of magnitude. This was attributed to the formation of a Ti-rich phase at the surface by the reaction between the Co–Ti–Si phase and CoSi2 at 900 °C. The Ti-rich phase acted as a dopant sink, and suppressed the diffusion of boron to the CoSi2/Si interface. This caused very shallow junction depth with a low boron concentration at the region directly below the Ti-rich phase, followed by generation of a large reverse leakage current. © 2000 American Vacuum Society.