Method for forming shallow trench isolation structure and method for manufacturing semiconductor device

The invention discloses a manufacturing method for forming a shallow trench isolation structure and a method for manufacturing a semiconductor device. The method for forming the shallow trench isolation structure comprises the steps of: providing a silicon wafer; forming a semiconductor substrate on the silicon wafer; etching the semiconductor substrate, and forming at least 100 trenches which aresymmetrically distributed around the center of the silicon wafer in the semiconductor substrate of a central region and an edge region of the silicon wafer; forming side walls and bottom surface padoxide layers which cover the trenches in the trenches, wherein the thicknesses of the pad oxide layers formed in the trenches of the edge region of the silicon wafer are greater than those of the padoxide layers formed in the trenches of the central region of the silicon wafer; and filling oxide on the pad oxide layers in the trenches to ensure that the surfaces of the oxide in the trenches and the surface of the semiconductor substrate are on the same plane. The methods improve the deformation phenomenon of the silicon wafer, and ensure that the deformation of the silicon wafer is reduced, thereby improving the utilization rate of the edge region of the silicon wafer.