We present a novel approach to produce a micromachined low cost hotplate gas sensor with reduced number of technology steps. The basic idea was to realize a simple device on common silicon substrates using conventional photolithography, sputtering and evaporation techniques. Two main performance parameters were targeted: the power consumption should not exceed 200 mW for an operation at 350 degree(s)C-400 degree(s)C and the thermal response time should be faster than 1 second. Fast thermal time constants allows the operation of device in temperature pulse mode. The first step of the development was the theoretical determination of the power consumption of the micromachined substrates, even temperature distribution on the sensitive area and sufficient mechanical stability. For this we build models describing the thermal behavior of the devices by means of the finite element method (FEM) and corresponding resistance-capacitor-networks (RC-network). Then we developed technological processes to fabricate sensor structures according to the optimal geometry resulting from the model calculations. A first prototype is introduced in this publication.© (2002) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.