Method for patterning a substrate using a layer with multiple materials

A method of patterning a substrate, the method comprising:

• forming mandrels on a target layer of a substrate, the mandrels being comprised of at least two layers of material, the mandrels including a bottom layer comprised of a first material, and a top layer comprised of a second material different than the first material, the target layer being comprised of a fifth material;
• forming sidewall spacers on sidewalls of the mandrels, the sidewall spacers comprised of a third material;
• depositing a fill material on the substrate that at least partially fills open spaces defined between the sidewall spacers, the fill material being comprised of a fourth material, wherein the first material, the third material and the fourth material have different etch resistivities compared to each other for one or more particular etch chemistries;
• and
• executing a chemical-mechanical polishing step that uses the bottom layer of the mandrels as a planarization stop material layer, the chemical-mechanical polishing step removing the third material above a top surface of the bottom layer of the mandrels such that the bottom layer of the mandrels, the sidewall spacers, and the fill material are at a same vertical height.