A patterning method is provided. First, a material layer is formed on a substrate. Thereafter, an ashable layer is formed on the material layer. Afterwards, a patterned transfer layer is formed on the ashable layer, wherein the patterned transfer layer has a critical dimension less than the exposure limit dimension. Further, the ashable layer is patterned using the patterned transfer layer or a complementary layer of the patterned transfer layer as a mask, so as to form a patterned ashable layer. The material layer is then patterned using the patterned ashable layer as a mask.