A semiconductor device includes a substrate, a first fin, and a second fin. The first and second fins are spaced apart from each other in a first direction on the substrate and extend in a second direction intersecting the first direction. The semiconductor device further includes a first shallow trench formed between the first and second fins, and a field insulating film which fills at least a part of the first shallow trench. The field insulating film includes a first portion, a second portion adjacent to the first portion, and a third portion adjacent to the second portion and adjacent to a side wall of the first shallow trench. The first portion includes a central portion of an upper surface of the field insulating film in the first direction. The upper surface of the field insulating film is in a shape of a brace recessed toward the substrate.