Semiconductor device having silicides and methods of manufacturing the same

A semiconductor device, comprising:

• a substrate with a PMOSFET region and an NMOSFET region;
• a plurality of first active patterns on the PMOSFET region and second active patterns on the NMOSFET region;
• a first source/drain pattern on the plurality of first active patterns and a second source/drain pattern on the plurality of second active patterns;
• a first channel pattern on each of the plurality of first active patterns and a second channel pattern on each of the plurality of second active patterns, each of the first and second channel patterns including a plurality of semiconductor patterns that are vertically stacked and spaced apart from each other;
• a first metal silicide layer and a second metal silicide layer on the first and second source/drain patterns, respectively;
• and
• first and second contacts in contact with the first and second metal silicide layers, respectively,
• wherein each of the first and second metal silicide layers includes:
• a first portion on an upper portion of a corresponding one of the first and second source/drain patterns;
• and
• a second portion on the upper portion and between a corresponding one of the first and second contacts and the corresponding one of the first and second source/drain patterns,
• wherein a thickness of the second portion of the first metal silicide layer is different from a thickness of the second portion of the second metal silicide layer.