Method for preparing semiconductor structure and semiconductor structure

A method for preparing a semiconductor structure, comprising:

• providing a substrate which comprises a device region and a shallow trench isolation region surrounding the device region, wherein the device region is exposed from a surface of the substrate;
• depositing a barrier layer on the substrate, wherein the barrier layer covers at least the device region, and a thickness of the barrier layer is 5 nm to 10 nm;
• thermally oxidizing part of the substrate in the device region by an in-situ steam generation process to form an initial oxide which is located between a remaining part of the substrate in the device region and the barrier layer, and in contact with the barrier layer;
• and removing the barrier layer by using an etching process;
• and removing part of the initial oxide and a remaining part of the initial oxide being formed as a device oxide, wherein a thickness of the initial oxide is less than or equal to 6 nm and a thickness of the device oxide is 1 nm to 3 nm.