Method for forming a semiconductor structure

A method for forming a semiconductor structure, comprising:

• providing a substrate having a memory array region and a peripheral region thereon;
• forming a memory structure on the substrate within the memory array region, wherein a step height is formed between the memory array region and the peripheral region;
• blanketly depositing a dielectric layer over the memory array region and the peripheral region, wherein the dielectric layer covers the memory structure;
• performing a reverse etching process to remove a portion of the dielectric layer from a central area of the memory array region, thereby forming an upwardly protruding wall structure along a perimeter of the memory array region, wherein a remaining thickness of the dielectric layer within the central area of the memory array region is equal to a combination of a polishing buffer thickness and a target thickness;
• subjecting the dielectric layer to a first polishing process to remove the upwardly protruding wall structure from the memory array region;
• and
• subjecting the dielectric layer to a second polishing process to remove an upper portion of the dielectric layer having the polishing buffer thickness from the memory array region, wherein a remainder of the dielectric layer within the memory array region has the target thickness above the memory structure.