| abstract |
Structures and formation methods of a semiconductor device structure are provided. The semiconductor device structure includes a substrate including a first fin portion, a first nanostructure over the first fin portion. The first nanostructure has a dumbbell shape. The first nanostructure includes a semiconductor material layer over the first fin portion, and a cladding layer surrounding the semiconductor material layer. The semiconductor material layer has a rectangular shape, and the cladding layer has a hexagonal or quadrilateral shape. The semiconductor device structure includes a first gate structure surrounding the first nanostructure. |