In order to reduce PtSi Schottky barrier height (SBH) for electron, we investigated modulation of PtSi work function by alloying with low work function metal, such as Hf (3.9eV) and Yb (2.7eV). Pt (10-20nm)/Hf, Yb (0-10nm)/n-Si(100) stacked structures were in-situ deposited at room temperature by RF magnetron sputtering method. In case of Pt_xHf_1-xSi formed at 400°C/60min annealing in N₂, SBH for electron was reduced from 0.85eV to 0.53eV with Hf thickness without increase of sheet resistance. Yb incorporation also affected the SBH modulation, however, the sheet resistance increased with increase of Yb thickness.