Semiconductor devices

A semiconductor device comprising:

• a substrate comprising an active region extending in a first direction;
• a gate structure on the substrate, intersecting the active region and extending in a second direction;
• and
• a source/drain region provided in a recess region defined by the active region adjacent the gate structure,
• wherein the source/drain region comprises:
• a first semiconductor layer on inner side surface of the recess region;
• diffusion barrier layers on upper ends of the first semiconductor layer and extending in directions oblique to the first direction;
• and
• a second semiconductor layer on the diffusion barrier layers and the first semiconductor layer, and
• wherein the diffusion barrier layers are spaced apart from each other in the source/drain region in the first direction.

A semiconductor device comprising:

• a substrate comprising an active region extending in a first direction;
• a gate structure on the substrate, intersecting the active region, and extending in a second direction;
• a plurality of channel layers on the active region, spaced apart from each other in a third direction perpendicular to an upper surface of the substrate, and surrounded by the gate structure;
• and
• a source/drain region on the active region adjacent the gate structure, and connected to the plurality of channel layers,
• wherein the source/drain region comprises:
• a first semiconductor layer on side surfaces of the plurality of channel layers;
• a second semiconductor layer on the first semiconductor layer;
• and
• a plurality of diffusion barrier layers between the first semiconductor layer and the second semiconductor layer.