There are provided methods of fabricating a semiconductor device using a sacrificial layer. The methods provide an approach to maintaining thickness distribution of the interlayer insulating layers below a sacrificial layer uniform on an overall surface of a semiconductor substrate during performing a chemical mechanical polishing (CMP) process in a damascene process. To this end, the method includes forming a pad layer, a pad interlayer insulating layer, an etch stop layer pattern, a planarized interlayer insulating layer and a sacrificial layer sequentially on a semiconductor substrate. At least one trench is formed in the sacrificial layer and the planarized interlayer insulating layer. A via contact hole is formed in the etch stop layer pattern, the pad interlayer insulating layer, and the pad layer to be disposed below the trench. A diffusion barrier layer and a conductive layer are sequentially formed to fill the trench and the via contact hole. A CMP process is performed on the conductive layer, the diffusion barrier layer, and the sacrificial layer.