Structural, morphological, and electrical measurements have been carried out on SnO 2 multilayer thin film grown by the rheotaxial growth and thermal oxidation method on Al 2 O 3 substrates. The analysis of X-ray and electron diffraction patterns shows that, in addition to the SnO 2 cassiterite phase, a contribution from another SnO 2 phase is present, which can be related to cassiterite by introducing microtwinning effects. The electrical measurements show that these thin films have a higher sensitivity towards CO with respect to the conventional single layer SnO 2 sensors.