A semiconductor device includes a metal oxide semiconductor device disposed over a substrate and an interconnect plug. The metal oxide semiconductor device includes a gate structure located on the substrate and a raised source/drain region disposed adjacent to the gate structure. The raised source/drain region includes a top surface above a surface of the substrate by a distance. The interconnect plug connects to the raised source/drain region. The interconnect plug includes a doped region contacting the top surface of the raised source/drain region, a metal silicide region located on the doped region, and a metal region located on the metal silicide region.