The present disclosure provides a method in accordance with some embodiments. The method includes forming a mandrel over a substrate, the mandrel having a first sidewall and a second sidewall opposing the first sidewall; forming a first fin on the first sidewall and a second fin on the second sidewall; depositing a dielectric material covering the first fin, the second fin, and the mandrel; partially removing the dielectric material, thereby exposing the second fin; etching the second fin without etching the first fin and the mandrel; removing the dielectric material; and removing the mandrel.