A semiconductor device includes a substrate, a first fin structure, an electrical contact structure and a gate structure. The first fin structure includes a horizontal fin structure extending along a first direction and a vertical fin structure extending along a second direction. The substrate has a first region and a second region. A portion of the horizontal fin structure and the vertical fin structure are disposed in the first region, and the electrical contact structure directly covers the horizontal fin structure and the vertical fin structure within the first region. The gate structure partially overlaps the horizontal fin structure within the second region.