A semiconductor device includes first active patterns and second active patterns on a substrate, a first source/drain region on the first active patterns, a second source/drain region on the second active patterns and a device isolation layer filling a first trench between adjacent ones of the first active patterns and a second trench between adjacent ones of the second active patterns. A liner layer is disposed on the device isolation layer between the adjacent ones of the second active patterns. The device isolation layer between the adjacent ones of the first active patterns has a recess therein under the first source/drain region and a bottom surface of the liner layer between the adjacent ones of the second active patterns is higher than the recess.