Gas sensor device and method of manufacturing the same

A gas sensor device (100) is configured to measure a predetermined gas of interest and comprises an enclosure (101) comprising a semiconductor substrate (102) and defining a first cavity (124), an optically transmissive second closed cavity (126) and a third cavity (128). The second cavity (126) is interposed between the first and third cavities (124, 128). The first cavity (124) comprises an inlet port (130) for receiving a gas under test, an outlet port (132) for venting the gas under test. The first cavity (124) also comprises an optical source (112) and a measurement sensor (114). The second cavity (126) is configured as a gaseous filter comprising a volume of the gas of interest sealingly disposed in the second cavity (126), and the third cavity (128) comprises a reference measurement sensor (116) disposed therein.