Provided is a method of manufacturing a semiconductor device. In the method, after a thin liner is formed on a substrate on which a lower interconnection is formed, a silicon source is supplied to form a silicide layer under the liner by a reaction between the silicon source and the lower interconnection, and the silicide layer is nitrided and an etch stop layer is formed. Therefore, the lower interconnection is prevented from making contact with the silicon source, variations of the surface resistance of the lower interconnection can be prevented, and thus high-speed devices can be fabricated.