The present disclosure provides a method of manufacturing a semiconductor structure. The method includes providing a substrate defined with a peripheral region and an array area at least partially surrounded by the peripheral region; disposing an insulating layer over the substrate; disposing a capping layer over the insulating layer; disposing a hardmask stack on the capping layer; patterning the hardmask stack; removing portions of the capping layer exposed through the hardmask stack; removing portions of the insulating layer exposed through the hardmask stack; removing portions of the substrate exposed through the capping layer and the insulating layer to form a plurality of fins in the array area and a first elongated member at least partially surrounding the plurality of fins; removing the hardmask stack; and forming an isolation over the substrate and surrounding the plurality of fins and the first elongated member.