SEMICONDUCTOR DEVICES

A semiconductor device includes an active region (105) on a substrate (101), a plurality of channel layers (141-143) spaced apart from each other, a gate structure (160) on the substrate (101), a source/drain region (150) on at least one side of the gate structure (160), and a contact plug (180) connected to the source/drain region (150). The contact plug (180) includes a metal-semiconductor compound layer (182) and a barrier layer (184) on the metal-semiconductor compound layer (182). The barrier layer (184) includes a first inclined surface (184_1) and a second inclined surface (184_2) positioned where the metal-semiconductor compound layer (182) and the barrier layer (184) directly contact each other. The barrier layer (184) includes first and second ends (184e1, 184e2) protruding towards the gate structure (160). The first and second ends (184e1, 184e2) are positioned at a level higher than an upper surface of an uppermost channel layer (143). An uppermost portion of the metal-semiconductor compound layer (182) is positioned at a level higher than an upper surface of the source/drain region (150).