A semiconductor device is disclosed. The semiconductor device may include a substrate including a first active pattern, the first active pattern vertically protruding from a top surface of the substrate, a first source/drain pattern filling a first recess, which is formed in an upper portion of the first active pattern, a first metal silicide layer on the first source/drain pattern, the first metal silicide layer including a first portion and a second portion, which are located on a first surface of the first source/drain pattern, and a first contact in contact with the second portion of the first metal silicide layer. A thickness of the first portion may be different from a thickness of the second portion.