A semiconductor device includes plurality of fin structures extending in first direction on semiconductor substrate. Fin structure's lower portion is embedded in first insulating layer. First gate electrode and second gate electrode structures extend in second direction substantially perpendicular to first direction over of fin structures and first insulating layer. The first and second gate electrode structures are spaced apart and extend along line in same direction. First and second insulating sidewall spacers are arranged on opposing sides of first and second gate electrode structures. Each of first and second insulating sidewall spacers contiguously extend along second direction. A second insulating layer is in region between first and second gate electrode structures. The second insulating layer separates first and second gate electrode structures. A third insulating layer is in region between first and second gate electrode structures. The third insulating layer is formed of different material than second insulating layer.