Bottom – up techniques were used to obtain gas sensors based on individual SnO2 nanowires placed over microhotplates with integrated heaters. These nanowires were electrically contacted to pre-patterned microelectrodes by means of Focused Ion Beam (FIB) nanofabrication methodologies. The performance of these sensors, which exhibit reproducible and stable responses, was evaluated as function of different gas atmospheres and dissipated power by the heater, demonstrating that this technological approach could be used to develop functional devices based on nanomaterials.