The invention relates to a self-aligned multi-patterning
mask layer and a formation method thereof. The formation method comprises the following steps that: a
semiconductor substrate is provided and a to-be-etched material layer is formed at the surface of the
semiconductor substrate; a sacrificial material layer is formed at the surface of the to-be-etched material layer;
etching is carried out on the sacrificial material layer to form a sacrificial layer, wherein the dimension of the portion, approaching the to-be-etched material layer, of the sacrificial layer is smaller than that of the portion, far away from the to-be-etched material layer, of the sacrificial layer; and a side wall is formed at the surface of the side wall of the sacrificial layer, wherein the portions of the two sides of the side wall are inclined towards the middle portion of the side wall from a position at the surface of the to-be-etched material layer to a position far away from the surface of the to-be-etched material layer. Because the portions of the two sides of the side wall are inclined towards the middle portion of the side wall and the profile shapes of the portions of the two sides of the side wall are identical with each other, the shapes of side walls of the to-be-etched material layer formed by
etching by using the side wall as the
mask subsequently are identical, so that the
electrical performance of the
semiconductor device that is formed subsequently is not influenced.