Two-dimensional (2D) transition-metal dichalcogenides have attracted significant attention as gas-sensing materials owing to their superior responsivity at room temperature and their possible application as flexible electronic devices. Especially, reliable responsivity and selectivity for various environmentally harmful gases are the main requirements for the future chemiresistive-type gas sensor applications. In this study, we demonstrate improved sensitivity of a 2D MoS 2 -based gas sensor by controlling the Schottky barrier height. Chemical vapor deposition process was performed at low temperature to obtain layer-controlled 2D MoS 2 , and the NO 2 gas responsivity was confirmed by the fabricated gas sensor. Then, the number of MoS 2 layers was fixed and the types of electrode materials were varied for controlling the Schottky barrier height. As the Schottky barrier height increased, the NO 2 responsivity increased, and it was found to be effective for CO and CO 2 gases, which had little reactivity in 2D MoS 2 -based gas sensors.