There is provided a method for manufacturing a semiconductor device including a substrate including a plurality of active regions, a plurality of gate electrodes extending in a first direction to intersect a portion of the plurality of active regions, and including first and second gate electrodes disposed to be adjacent to each other in the first direction, a gate isolation portion disposed between the first and second gate electrodes. The gate isolation portion includes a first layer and second layers disposed on both ends of the first layer in a second direction perpendicular to the first direction.