FIN ISOLATION STRUCTURE FOR FINFET AND METHOD OF FORMING THE SAME

A semiconductor device structure is provided. The semiconductor device structure includes a substrate having adjacent first and second fins protruding from the substrate. A first gate structure and a second gate structure are across the first and second fins, respectively. An insulating structure is formed between the first gate structure and the second gate structure and includes a first insulating layer separating the first fin from the second fin, a capping structure formed in the first insulating layer, and a second insulating layer covered by the first insulating layer and the capping structure.