Hybrid-gate suspended field-effect transistors for gas-sensing

State of the art microsensors for gas detection are mainly based on conductivity measurements at deviated temperatures (300/spl deg/C-800/spl deg/C). In comparison field effect devices exploiting the gas induced work function shift of materials exhibit several superior features, such as low power consumption due to low temperature operation, and sensitivity to a wide range of reaction mechanisms. A suspended gate design for a MOSFET (metal-oxide-semiconductor field effect transistor) permits the access of gas species to the inner surface of the gate which acts as the chemical sensitive layer. This enables the incorporation of almost all sensitive materials. The design requirements for the silicon device structure, the hybrid mounting technique, and some typical results are presented.