Gas sensing devices are widely used in various applications such as environmental monitoring, safety devices, smart applications, among others. Today’s widespread chemiresistive gas sensors are based on semiconductive metal oxides that change their electrical resistance due to adsorption reactions of gas molecules on its surface. Despite some commercial success and the recent scientific interest, there is still a lack of methods to characterize the microstructure of the gas sensing materials during operation. Within this thesis, a new approach to characterize gas sensing thin films by the means of Raman spectroscopy is conceived and applied. The designed Raman set-up enables the characterization of the microstructure and the electric properties of the gas sensing materials (CuO and ZnO) for different gas atmospheres. First, the author describes in detail the thin-film processing done by spray pyrolysis technique and photolithography for CuO and ZnO. Then, a detailed description of all included parts of the Raman setup and a manual for its assembly, including a proof of functionality, is provided. Finally, the set-up is used to investigate the interaction between target gases and metal oxide surfaces were in-situ by Raman spectroscopy. The obtained spectra of the metal oxide thin-films CuO and ZnO were studied and related to surface-gas interactions found in literature. The results demonstrate that Raman spectroscopy is a highly useful tool also for the in-situ measurement of very thin films used specifically for chemical sensors.