A method for manufacturing a semiconductor structure, comprising: providing a substrate , an isolation trench being formed on the substrate ; forming a silicon-rich isolation layer in the isolation trench , the silicon-rich isolation layer covering an inner surface of the isolation trench ; characterized in that the method further comprises: forming a second oxide layer in the isolation trench , the second oxide layer covering the silicon-rich isolation layer , wherein the silicon-rich isolation layer is oxidized by an in-situ steam generation process, after the in-situ steam generation process is finished, at least part of the silicon-rich isolation layer has been oxidized into the first oxide layer ; forming a third oxide layer in the isolation trench , the third oxide layer covering the second oxide layer , wherein after the third oxide layer is formed, the silicon-rich isolation layer has been completely oxidized into the first oxide layer , and the first oxide layer , the second oxide layer , and the third oxide layer serving as the first isolation oxide layer ; and forming a second isolation oxide layer in the isolation trench , the second isolation oxide layer covering the first isolation oxide layer , and the first isolation oxide layer and the second isolation oxide layer serving as the isolation oxide layer , wherein, the isolation oxide layer fills up the isolation trench . providing a substrate , an isolation trench being formed on the substrate ; forming a silicon-rich isolation layer in the isolation trench , the silicon-rich isolation layer covering an inner surface of the isolation trench ; characterized in that the method further comprises: forming a second oxide layer in the isolation trench , the second oxide layer covering the silicon-rich isolation layer , wherein the silicon-rich isolation layer is oxidized by an in-situ steam generation process, after the in-situ steam generation process is finished, at least part of the silicon-rich isolation layer has been oxidized into the first oxide layer ; forming a third oxide layer in the isolation trench , the third oxide layer covering the second oxide layer , wherein after the third oxide layer is formed, the silicon-rich isolation layer has been completely oxidized into the first oxide layer , and the first oxide layer , the second oxide layer , and the third oxide layer serving as the first isolation oxide layer ; and forming a second isolation oxide layer in the isolation trench , the second isolation oxide layer covering the first isolation oxide layer , and the first isolation oxide layer and the second isolation oxide layer serving as the isolation oxide layer , wherein, the isolation oxide layer fills up the isolation trench . forming a second oxide layer in the isolation trench , the second oxide layer covering the silicon-rich isolation layer , wherein the silicon-rich isolation layer is oxidized by an in-situ steam generation process, after the in-situ steam generation process is finished, at least part of the silicon-rich isolation layer has been oxidized into the first oxide layer ; forming a third oxide layer in the isolation trench , the third oxide layer covering the second oxide layer , wherein after the third oxide layer is formed, the silicon-rich isolation layer has been completely oxidized into the first oxide layer , and the first oxide layer , the second oxide layer , and the third oxide layer serving as the first isolation oxide layer ; and forming a second isolation oxide layer in the isolation trench , the second isolation oxide layer covering the first isolation oxide layer , and the first isolation oxide layer and the second isolation oxide layer serving as the isolation oxide layer , wherein, the isolation oxide layer fills up the isolation trench . <EOS>