Preparation method of groove

The invention relates to the technical field of semiconductors, in particular to a preparation method of a groove. The preparation method of the groove comprises the following steps: providing a substrate, wherein the substrate comprises a region to be etched for the first time; forming a photoresist layer on the substrate, wherein the photoresist layer covers the upper surface of the substrate; setting a Star mark at a position, corresponding to the first to-be-etched region, of the photoresist layer, wherein the width of the Star mark is smaller than that of the first to-be-etched region; photoetching is carried out on the Star mark and the photoresist layer to obtain a patterned photoresist layer, a first opening is formed in the position, corresponding to the first to-be-etched area, of the patterned photoresist layer, and a residual photoresist layer with a preset thickness is arranged in the position, corresponding to the Star mark, in the first opening; the substrate is etched based on the patterned ph