Etching method

The invention discloses an etching method, which is applied to a preparation process of a FinFET device, and comprises the steps: forming a first insulating layer on a substrate, wherein the first insulating layer covers a first fin structure and a second fin structure on the substrate, the first fin structure being higher than the second fin structure, the thicknesses of the first insulating layer in different areas on the substrate are different, and an oxide layer, a first hard mask layer and a second hard mask layer are sequentially formed on the first fin structure; performing first-time planarization processing on the first insulating layer until the first hard mask layer is exposed; removing the first fin structure, the second fin structure and the first insulating layer in the target region, and forming a groove in the target region; forming a second insulating layer, wherein the second insulating layer fills the groove; and carrying out second-time planarization treatment until the first hard mask la