A semiconductor device structure is provided. The semiconductor device structure includes a first device formed over a substrate, wherein the first device includes a first fin structure and a first S/D structure formed over the first fin structure. The semiconductor device structure includes a second device formed over or below the first device, and the second device includes a plurality of second nanostructures stacked in a vertical direction. The semiconductor device structure also includes a second S/D structure formed over the second nanostructures, and the second S/D structure is directly above or below the first S/D structure.