Multi-gate field-effect transistor and process thereof

A Multi-Gate Field-Effect Transistor includes a fin-shaped structure, a gate structure, at least an epitaxial structure and a gradient cap layer. The fin-shaped structure is located on a substrate. The gate structure is disposed across a part of the fin-shaped structure and the substrate. The epitaxial structure is located on the fin-shaped structure beside the gate structure. The gradient cap layer is located on each of the epitaxial structures. The gradient cap layer is a compound semiconductor, and the concentration of one of the ingredients of the compound semiconductor has a gradient distribution decreasing from bottom to top. Moreover, the present invention also provides a Multi-Gate Field-Effect Transistor process forming said Multi-Gate Field-Effect Transistor.