Abstract: A method for manufacturing semiconductor shallow trench isolation is performed as follows. First, a semiconductor substrate including at least one shallow trench is provided, and the shallow trench is filled with Spin-On-Dielectric (SOD) material, e.g., polysilazane, to form a SOD material layer. Then, the SOD material layer is subjected to a planarization process. Oxygen ions are implanted into the SOD material layer to a predetermined depth, and a high temperature process is performed afterwards to transform the portion of the SOD material layer having oxygen ions into a silicon oxide layer. The oxygen ions can be implanted by plasma doping, immersion doping or ion implantation.