A SnOx thin film with a thickness of 400 ± 20 nm was deposited on a glass substrate and thermally oxidized at temperatures ranging from 573 K to 673 K. The structural surface morphology of SnOx thin films is checked. X-ray diffraction analysis indicated that films oxidized at 573K and 623K contain SnO, Sn3O4, and SnO2, as well as residual metallic tin. When the oxidation temperature was increased to 673K, the SnO₂ peaks became more prominent while the metallic Sn peak weakened. AFM studies indicated that the roughness of the films changed with different oxidation temperatures, which means that the oxidation temperature has a direct effect on the surface nature of the SnOx films. On the other hand, films oxidized at 673K (SnO2) are useful in gas sensor applications. The sensitivity (S) of the sensors manufactured for Oxidizing Gas (NO₂) was measured at room temperature and 373 and 473 K.  The maximum sensitivity appeared for the sample at a 373 K operating temperature, which is 7.33%. The sample exhibited the lowest response time at an operating temperature of 473 K.