Manufacturing method of semiconductor structure

A manufacturing method of a semiconductor structure, comprising:

• providing a substrate;
• forming two shallow trench isolation structures in the substrate, wherein a first region, a second region and a third region are defined between the two shallow trench isolation structures, wherein the second region is located between the first region and the third region;
• forming an oxide layer in the first region, the second region and the third region, and the oxide layer directly contacts the two shallow trench isolation structures;
• removing the oxide layer in the second region, and the remaining oxide layer is located in the first region and the third region;
• and
• forming another oxide layer in the first region, the second region and the third region to form a thick oxide layer in the first region and the third region respectively, and forming a thin oxide layer in the second region, wherein the thickness of the thick oxide layer in the first region is greater than the thickness of the thin oxide layer in the second region.