A method for forming a semiconductor device structure, comprising the steps of independently forming source/drain surface metal silicide layers and a fully silicided metal gate in a polysilicon gate stack. Specifically, one or more sets of spacer structures are provided along sidewalls of the polysilicon gate stack after formation of the source/drain surface metal silicide layers and before formation of the silicided metal gate, in order to prevent formation of additional metal silicide structures in the source/drain regions during the gate salicidation process. The resulting semiconductor device structure includes a fully silicide metal gate that either comprises a different metal silicide material from that in the source/drain surface metal silicide layers, or has a thickness that is larger than that of the source/drain surface metal silicide layers. The source/drain regions of the semiconductor device structure are devoid of other metal silicide structures besides the surface metal silicide layers.