The present disclosure provides a fabrication method for forming a semiconductor device, including: forming a substrate, the substrate including first fins, second fins, and a first trench located in the substrate between a first fin and an adjacent fin; forming a first mask layer on the substrate, the first fins, and the second fins; and removing portions of the first mask layer neighboring a first trench to expose a portion of a top surface of a first fin and a portion of a top surface of the adjacent second fin to form a first opening, a portion of the top surface of the first fin covered by a remaining portion of the first mask layer being a first fin device region, a portion of the top surface of the second fin covered by a remaining portion of the first mask layer being a second fin device region.