A semiconductor device including at least one conductive structure is provided. The conductive structure includes a silicon-containing conductive layer, a refractory metal salicide layer and a protection layer. The refractory metal salicide layer is disposed over the silicon-containing conductive layer. The protection layer is disposed over the refractory metal salicide layer. Another semiconductor device including at least one conductive structure is also provided. The conductive structure includes a silicon-containing conductive layer, a refractory metal alloy salicide layer and a protection layer. The refractory metal alloy salicide layer is disposed over the silicon-containing conductive layer. The refractory metal alloy salicide layer is formed from a reaction of silicon of the silicon-containing conductive layer and a refractory metal alloy layer which includes a first refractory metal and a second refractory metal. The protection layer is disposed over the refractory metal alloy salicide layer.