A method of fabricating a semiconductor integrated circuit (IC) device can include forming a first silicide layer on at least a portion of a transistor on a substrate, forming nitrogen in the first silicide layer to form a second silicide layer, forming a first stress layer having a tensile stress on the substrate having the transistor formed thereon, and irradiating the first stress layer with ultraviolet (UV) light to form a second stress layer having greater tensile stress than the first stress layer.