Disclosed in the embodiments of the present disclosure is a method for preparing a semiconductor device, the method comprising: forming a gate insulating material layer on a substrate; forming a gate material layer on the gate insulating material layer; and executing an etching process on the gate material layer and the gate insulating material layer to form a gate layer and a gate insulating layer, wherein in a direction parallel to the length of a channel, each of the gate insulating layer and the gate layer comprises a first end and a second end which are opposite each other; the first end of the gate insulating layer is recessed inwards by a preset length relative to the first end of the gate layer; and the second end of the gate insulating layer is recessed inwards by the preset length relative to the second end of the gate layer.