Method for manufacturing shallow trench isolation structure, shallow trench isolation structure and semiconductor structure

Abstract

A method for manufacturing a shallow trench isolation structure includes: providing a substrate and forming multiple first trenches in the substrate, in which a cross-sectional width of each first trench increases downward along a vertical direction; forming a continuous first isolation layer on a top of the substrate and inner sides of the multiple first trenches by a deposition process, in which parts of the first isolation layer located in the first trenches form second trenches, and in which a cross-sectional width of each second trench remains constant downward along the vertical direction; and forming a continuous second isolation layer on a surface of the first isolation layer by an ISSG process, in which parts of the second isolation layer located in the second trenches completely fill up the second trenches.