Abstract: Thin tin oxide films are used as spacers in semiconductor device manufacturing. In one implementation, thin tin oxide film is conformally deposited onto a semiconductor substrate having an exposed layer of a first material (e.g., silicon oxide or silicon nitride) and a plurality of protruding features comprising a second material (e.g., silicon or carbon). For example, 10-100 nm thick tin oxide layer can be deposited using atomic layer deposition. Next, tin oxide film is removed from horizontal surfaces, without being completely removed from the sidewalls of the protruding features. Next, the material of protruding features is etched away, leaving tin oxide spacers on the substrate. This is followed by etching the unprotected portions of the first material, without removal of the spacers. Next, underlying layer is etched, and spacers are removed. Tin-containing particles can be removed from processing chambers by converting them to volatile tin hydride.