Suspended-Gate Polysilicon Thin Film Transistor as Generic Structure for Highly Sensitive Charged Ambience Sensors

Suspended-Gate Polysilicon Thin Film Transistors, namely SGTFT, are fabricated at a maximum temperature of 600°C on glass substrate. When using sub-micronic gap, high field effect induces large shift of the transfer characteristics due to any charge variation inside the gap. The device is used in measurements of pH of different solutions with high sensitivity (~250 mV/pH), 4 times the theoretical Nernstian response and the usual value given by the known transducers. This high sensitivity, un-reached until now, is explained by the charge distribution induced by the high applied field. Application of the device is extended to DNA recognition with high and rapid answer. Whatever the application, SGTFT is sensitive to charge variation. Selectivity can be insured by the detection principle that is based on the couple DNA/complementary DNA in the case of DNA recognition or antibody / antigene in the case of proteins.