In this work, multilevel switching was achieved by a strategically designed alternative multi-layer structure with pure and Mn-doped SnO₂. In this multilayer structure, by utilizing the pure SnO₂ layer as an ionic defect diffusion barrier, the migration of ionic defects from the doped layers can be controlled and the intermediate resistance states were stabilized. The multilevel devices exhibit superior performances with a high ON/OFF ratio, low operation voltage and excellent retention. Such an alternative multi-layer structure could be a potential strategy for achieving high-density memories.