A semiconductor device includes a first gate structure disposed on a substrate and extending in a first direction. The first gate structure includes a first gate electrode, a first cap insulating layer disposed over the first gate electrode, first sidewall spacers disposed on opposing side faces of the first gate electrode and the first cap insulating layer and second sidewall spacers disposed over the first sidewall spacers. The semiconductor device further includes a first protective layer formed over the first cap insulating layer, the first sidewall spacers and the second sidewall spacers. The first protective layer has a n-shape having a head portion and two leg portions in a cross section along a second direction perpendicular to the first direction.