The role of Auger electron spectroscopy in evaluating and developing specific fabrication steps for gas sensor microarrays is exemplified. Using Auger line scans, the shadow mask sputter technique is evaluated regarding the geometrical integrity of the electrode pattern. The technique of ion beam assisted chemical vapor deposition is applied to coat the microarray with an ultrathin gas-permeable SiO2 membrane varying in thickness across the sensor. A quantification method for the determination of the thickness profiles of the SiO2 selector membrane and the carbon contamination layer is presented. Moreover, the influence of thermal annealing and long-term gas exposure on the device quality is studied.