Semiconducting metal oxides are widely used in gas sensing devices for monitoring process environments in safety devices, among others. These so-called solid-state gas sensors change their material properties, in particular their electrical conductivity due to chemisorption reactions between the sensing metal oxide material and environmental gas molecules. Novel metal nano clusters deposited on gas sensing metal oxide surfaces can enhance the performance of gas sensors, i.e. in terms of gas selectivity. Within this thesis, the author describes in detail the thin-film processing of tin oxide (SnOx) for the application as gas sensing material via reactive DC magnetron sputter deposition. The deposited films were analyzed in detail by scanning electron microscopy, X-ray diffraction, Raman spectroscopy, and Elastic Recoil Detection Analysis. The obtained data of the investigated SnOx films was studied and related to the influence of the deposition parameters. The results show that reactive DC magnetron sputter deposition is a promising method to fabricate gas sensing thin films. It allows the deposition of clean contamination free SnOx films with the required characteristics. In addition, a first attempt to deposit Au nano clusters was carried out. The results lead to the conclusion, that further intense studies and improvements of methods, such as gas phase synthesis, should provide the possibilities to fabricate ideal nano clusters for the functionalization of gas sensing metal oxides.