Semiconductor devices and methods of fabricating semiconductor devices are disclosed. A disclosed semiconductor device includes a silicon substrate, a source region and a drain region. A gate electrode is formed on the silicon substrate. Also, a metal silicide layer is formed on each of the gate electrode, the source region, and the drain region. The metal silicide layer has a thickness uniformity of about 1.about.20%. A disclosed fabrication method includes forming a metal layer on a silicon substrate having a gate electrode, a source region, and a drain region; performing a plasma treatment on the metal layer; forming a protective layer on the metal layer; and heat treating the silicon substrate on which the protective layer is formed to thereby form a metal silicide layer. A gas that includes nitrogen is used as a plasma gas during the plasma treatment.