Some embodiments of the present disclosure provide a gas sensor in an IOT. The gas sensor includes a substrate, a conductor disposed above the substrate, and a sensing film disposed over the conductor. The conductor has a top-view pattern including a plurality of openings, a minimal dimension of the opening being less than about 4 micrometer; and a perimeter enclosing the opening. Some embodiments of the present disclosure provide a method of manufacturing a gas sensor. The method includes receiving a substrate; forming a conductor, over the substrate; patterning the conductor to form a plurality of openings in the conductor by an etching operation, and forming a gas-sensing film over the conductor. The openings are arranged in a repeating pattern, and a minimal dimension of the opening being about 4 micrometer.