A semiconductor device having a silicide-blocking layer is provided. The device includes a field oxide layer defining an active region, source/drain regions in the active region of a substrate, a gate oxide layer and a gate electrode on the substrate between the source/drain regions, dielectric spacers on sidewalls of the gate electrode, and a silicide layer on both the gate electrode and the source/drain regions. The device also includes the silicide-blocking layer formed over the border between the field oxide layer and the source/drain regions. The silicide-blocking layer covers edges of the source/drain regions, obstructing the extension of the silicide layer.