The invention relates to a gate structure and a preparation method thereof, and a
semiconductor device, and the method comprises the steps: providing a substrate which comprises a
semiconductor layer; the
semiconductor layer has an initial width and an initial surface quality; n target process steps are executed to form a gate conductive layer, and the step of executing the ith target process step comprises the steps that an
oxidation process is adopted to form an ith sacrificial
oxide layer covering the outer surface of the semiconductor layer; at least part of the ith sacrificial
oxide layer is removed, i belongs to [2, N], and N belongs to a positive integer; after N times of target process steps, the remaining semiconductor layer is used for forming a gate conductive layer; the gate conductive layer has a target width and a
target surface quality; and forming an oxidation
protection layer covering the outer surface of the gate conductive layer. According to the method, the original one-
time Gate oxidation is replaced by two or more times of Gate oxidation, so that the damage caused by the poly gate in the
etching process can be more effectively repaired, and the CD of the poly gate can be controlled to a certain extent.