Miniaturized semiconductor gas sensors composed of microheater and a sensor electrode allowed a rapid heater switching, pulse-driven operation. SnO2 nanoparticles was fabricated on the gas sensor device, and the sensor was driven during heater on phase at elevated temperature. Additionally, the gas was introducing into the sensing layer during heater off phase, cooling the sensing layer. On the basis of the behavior of the electrical resistance under pulse-driving, we determined the various types of sensor responses to improve the gas sensing characteristics. The gas sensitivity was drastically enhanced by pulse-driving mode, because utility factor of the pulse-driven sensor was higher than that of conventional sensor. Additionally, newly gas sensing definition also enhanced the gas selectivity, because gas accumulates in the sensing layer during heater off phase. Therefore, pulse-driving mode improved the ability of semiconductor gas sensors.