Tin dioxide ($SnO_2$) thin films were prepared on Si(100) substrate by PE-ALD using the $DBDTA((CH_{3}CO_2)_{2}Sn[(CH_2)_{3}CH_3]_2)$ Precursor. The properties were studied as a function of source temperature, substrate temperature, and purging time. Scanning probe microscopic images at the source temperature $50^{circ}C$ and the substrate temperature $300^{circ}C$ shows lower roughness than those $40/60^{circ}C$ source and $200/400^{circ}C$ substrate temperature samples. The purging time for optimum process was 8sec and the deposition rate was about 1 nm per 10 cycles. The conductance of $SnO_2$ thin film showed a constant region in the range of $200^{circ}C;to;500^{circ}C$. The thin films deposited for 200 cycle show a better sensitivity to CO gas.