A compact microelectronic gas sensor module includes electrical contacts formed in such a way that they do not consume real estate on an integrated circuit chip. Using such a design, the package can be miniaturized further. The gas sensor is packaged together with a custom-designed Application Specific Integrated Circuit (ASIC) that provides circuitry for processing sensor signals to identify gas species within a sample under test. In one example, the output signal strength of the sensor is enhanced by providing an additional metal surface area in the form of pillars exposed to an electrolytic gas sensing compound, while reducing the overall package size. In some examples, bottom side contacts are formed on the underside of the substrate on which the gas sensor is formed. Sensor electrodes may be electrically coupled to the ASIC directly, or indirectly by vias.