Preparation method of semiconductor structure and semiconductor structure

The invention provides a preparation method of a semiconductor structure and the semiconductor structure, and particularly relates to the technical field of semiconductors. The preparation method comprises the following steps: providing a substrate; a first patterned photoresist layer is formed on the substrate, the first patterned photoresist layer is provided with an opening, and the opening exposes part of the substrate; performing fluorine ion implantation on the substrate in the opening by taking the first patterned photoresist layer as a mask to form a fluorine ion doped region; the first graphical photoresist layer is removed, the surface of the substrate is thermally oxidized to form an asymmetric gate oxide layer, and the thickness of the fluorine ion doped region corresponding to the asymmetric gate oxide layer is larger than the thickness of the other regions; forming a gate structure on the asymmetric gate oxide layer; and forming a drain electrode in the substrate on one side, corresponding to th