Semiconductor device structures are provided. The semiconductor device structure includes a first semiconductor wire over a semiconductor substrate. The first semiconductor wire has a first width and a first thickness. The semiconductor device structure also includes a first gate stack surrounding the first semiconductor wire. The semiconductor device structure further includes a second semiconductor wire over the semiconductor substrate. The first semiconductor wire and the second semiconductor wire include different materials. The second semiconductor wire has a second width and a second thickness. The first width is greater than the second width. The first thickness is less than the second thickness. In addition, the semiconductor device structure includes a second gate stack surrounding the second semiconductor wire.