Semiconductor structure and preparation method thereof

The invention provides a semiconductor structure and a preparation method thereof. The preparation method comprises the following steps: providing a substrate which comprises an insulating region, an active region and a first upper surface, the active region is adjacent to the insulating region, the insulating region is provided with an insulating groove, the insulating groove is filled with a dielectric material, the active region is provided with a grid electrode groove, and the grid electrode groove is filled with a grid electrode material; forming a hard mask on the substrate; and performing an etching process to partially remove portions of the dielectric material and the gate electrode material exposed by the hard mask to form a second upper surface of the dielectric material and a third upper surface of the gate electrode material, wherein the second upper surface and the third upper surface are approximately on the same plane and are approximately lower than the first upper surface. 本公开提供一种半导体结构及其制备方法