We have investigated the redistribution of uniformly doped As atoms (N D=4.0×1019 cm-3) in Si during Pd2Si formation with neutron activation analysis and the influence of the redistribution on contact resistivity. Some of the uniformly doped As atoms are pushed ahead into Si near the silicide-silicon interface during Pd2Si formation at 250°C. The amount of the redistributed As atoms increases with the thickness of Si consumed and reaches a peak concentration of 2.0×1020 cm- 3. Contact resistivity is reduced from the initial values of 3.8×10-5-4.1×10-4 Ω cm2 before silicide formation, to a final value of 1.8×10-6 Ω cm2 after complete reaction. The electrically active As atoms is estimated to be 50% of the total redistributed.