Semiconductor devices

A semiconductor device comprising:

• an active pattern including a lower pattern extending in a first direction and a plurality of sheet patterns spaced apart from the lower pattern in a second direction perpendicular to the first direction;
• a plurality of gate structures on the lower pattern to be spaced apart from each other in the first direction and including a gate electrode and a gate insulating layer, the gate electrode and the gate insulating layer surrounding the plurality of sheet patterns;
• a source/drain recess between an adjacent pair of the plurality of gate structures;
• and
• a source/drain pattern on the lower pattern in the source/drain recess and in contact with the sheet pattern,
• wherein the source/drain pattern includes:
• a semiconductor liner layer that extends along the source/drain recess, is in contact with the gate insulating layer, and includes silicon-germanium,
• a first semiconductor insertion layer on the semiconductor liner layer,
• a semiconductor filling layer including silicon-germanium on the first semiconductor insertion layer, and
• a semiconductor capping layer including silicon on the semiconductor filling layer, and
• wherein a germanium fraction of the first semiconductor insertion layer is less than a germanium fraction of the semiconductor liner layer and a germanium fraction of the semiconductor filling layer.

A semiconductor device comprising:

• an active pattern including a lower pattern, and a sheet pattern spaced apart from the lower pattern in a first direction;
• a gate structure on the lower pattern and including a gate electrode and a gate insulating layer that surrounds the sheet pattern, the gate electrode extending in a second direction perpendicular to the first direction;
• and
• a source/drain pattern on the lower pattern and in contact with the gate insulating layer,
• wherein the source/drain pattern includes:
• a semiconductor liner layer including an outer sidewall in contact with the gate insulating layer and an inner sidewall opposite to the outer sidewall,
• a first semiconductor insertion layer in contact with the semiconductor liner layer on the inner sidewall of the semiconductor liner layer,
• a second semiconductor insertion layer on the first semiconductor insertion layer, and
• a semiconductor filling layer on the second semiconductor insertion layer, and
• wherein the first semiconductor insertion layer covers at least a portion of the inner sidewall of the semiconductor liner layer,
• the second semiconductor insertion layer extends along at least a portion of a profile of the first semiconductor insertion layer,
• a germanium fraction of the first semiconductor insertion layer is greater than a germanium fraction of the semiconductor liner layer and is less than a germanium fraction of the semiconductor filling layer, and
• a germanium fraction of the second semiconductor insertion layer is less than the germanium fraction of the semiconductor liner layer and the germanium fraction of the first semiconductor insertion layer.