A semiconductor device with different configurations of contact structures and a method of fabricating the same are disclosed. The method includes forming first and second fin structures on a substrate, forming n- and p-type source/drain (S/D) regions on the first and second fin structures, respectively, forming first and second contact openings on the n- and p-type S/D regions, respectively, forming a carbon-based layer in the first and second contact openings, performing a remote plasma treatment with radicals on the carbon-based layer to form a remote plasma treated layer, selectively removing a portion of the remote plasma treated layer, forming a p-type work function metal (pWFM) silicide layer on the p-type S/D region, and forming an n-type work function metal (nWFM) silicide layer on the pWFM silicide layer and on the n-type S/D region.