The present disclosure provides one embodiment of a method making semiconductor structure. The method includes forming a composite stress layer on a semiconductor substrate, wherein the forming of the composite stress layer includes forming a first stress layer of a dielectric material with a first compressive stress and forming a second stress layer of the dielectric material with a second compressive stress on the first stress layer, the second compressive stress being greater than the first compressive stress; and patterning the semiconductor substrate to form fin active regions using the composite stress layer as an etch mask.