Modified ion sensitive field effect transistor sensors having an extended gate on a thick dielectric

Modified ion sensitive field effect transistors having an extended gate (EG) on a thick dielectric have been developed to obtain extremely high sensitivity. The capacitance of the EG is controlled to be very small via the thickness of the dielectric layer so that it may be ignored when compared with the gate capacitance of the transistor. As a result, the gate voltage can be fully dependent on the surface charge of the EG. When microalbumin protein of concentration 1 μg/ml on a monoclonal antibody of a microalbumin surface of the EG is injected, an extremely high sensitivity of 1800% is observed.