A semiconductor device includes a substrate including a peripheral region, a first active pattern on the peripheral region, the first active pattern having an upper portion including first semiconductor patterns and second semiconductor patterns, which are alternately stacked, a first gate electrode intersecting the first active pattern, a pair of first source/drain patterns provided at both sides of the first gate electrode, respectively, a first capping layer on the first active pattern, a second capping layer on the first capping layer, and a first gate insulating layer between the second capping layer and the first gate electrode. The first capping layer is between a sidewall of the first active pattern and the second capping layer. A concentration of germanium (Ge) of the first capping layer is greater than a concentration of germanium of the second capping layer.