Spacers (175) in a pitch multiplication process are formed without performing a spacer etch. Rather, mandrels (145) are formed over a substrate (110) and then the sides of the mandrels (145) are reacted, e.g., in an oxidization, nitridation, or silicidation step, to form a material that can be selectively removed relative to the unreacted portions of the mandrel (145). The unreacted portions are selectively removed to leave a pattern of free standing spacers (175). The free-standing spacers (175) can serve as a mask for subsequent processing steps, such as etching the substrate (110).