A MEMS gas sensor includes a photoacoustic sensor including a thermal emitter and an acoustic transducer, the thermal emitter and the acoustic transducer being inside a mutual measurement cavity. The thermal emitter includes a semiconductor substrate and a heating structure supported by the semiconductor substrate. The heating structure includes a heating element. The MEMS gas sensor further includes a chemical sensor thermally coupled to the heating element, and the chemical sensor including a gas adsorbing layer.