1. A patterning method, comprising: forming a mask layer and a plurality of first transfer patterns sequentially on a target layer; performing a first conversion process to consume surfaces of the first transfer patterns, so as to form a plurality of first conversion patterns on the surfaces of the first transfer patterns; filling a plurality of second transfer patterns in gaps between the first conversion patterns; removing the first conversion patterns; performing a second conversion process to consume surfaces of the first transfer patterns and the second transfer patterns, so as to form a plurality of second conversion patterns on the surfaces of the first transfer patterns and the second transfer patterns; filling a plurality of third transfer patterns in gaps between the second conversion patterns; removing the second conversion patterns; removing a portion of the mask layer, using the first transfer patterns, the second transfer patterns and the third transfer patterns as a mask, so as to form a patterned mask layer; and removing a portion of the target layer using the patterned mask layer as a mask.