A semiconductor device includes a first active pattern extending lengthwise along a first direction and a second active pattern extending lengthwise along the first direction and spaced apart from the first active pattern in the first direction. The device also includes a field insulating film between the first active pattern and the second active pattern. An upper surface of the field insulating film is lower than or coplanar with upper surfaces of the first and second active patterns. The device further includes an element isolation structure in an isolation trench in the first active pattern and the field insulating film. An upper surface of the element isolation structure is higher than the upper surfaces of the first and second active patterns.