A method for producing a multi-gate fin field-effect transistor (FinFET) is provided. The method includes forming a channel layer and a gate medium layer on a substrate; forming an amorphous silicon layer on the substrate, and etching the amorphous silicon layer, to form at least one fin; forming, by using an epitaxial growth process, a first protective layer from both sides to the middle of the substrate along a length direction of the at least one fin until a groove is formed in a middle location along the length direction of the at least one fin; forming a gate electrode layer on the substrate, performing planarization processing on the gate electrode layer to expose the first protective layer, and etching away the first protective layer by using an etching process, so as to form a gate electrode; and forming a source electrode and a drain electrode on the substrate.