Abstract: The present disclosure provides a method for improving residue formation after mandrel removal, including steps of: providing a TEOS layer, forming mandrel structures spaced apart from each other on the TEOS layer, and forming spacers on sidewalls of each of the mandrel structures; forming a first SOC layer to cover the surface of the TEOS layer, the mandrel structures, and the spacers of the mandrel structures, and forming a SOC structure that covers the spacers and exposes the top surfaces of the mandrel structures; removing the mandrel structures by etch along sidewalls of SOC structure, forming a first groove between two of the spacers on the sidewalls of the removed mandrel structures; forming a second SOC layer to cover the SOC structure and fill the first groove; performing top planarization of the second SOC layer until the top surface of the SOC structure is exposed.