The electrical and materials properties of ∼20nm nickel silicide films, formed at 300°C, on n+∕p and p+∕n junctions are investigated. The sheet resistance of the silicide on p+∕n junctions is found to be more than twice as high as that of the silicide on n+∕p junctions. Cross section transmission electron microscopy, Rutherford backscattering spectroscopy, and x-ray photoelectron energy spectroscopy reveal that a pure Ni2Si layer forms on n+∕p junctions while a thicker Ni2Si∕NiSi double layer (∼60% Ni2Si) forms on p+∕n junctions. But the electrical differences are found to correlate only with differences in grain size and dopant concentration in the silicide.