Modified ISFETs having an extended gate on the thick dielectric

Modified ISFETs having an extended gate on the thick dielectric has been developed to obtain the extremely high sensitivity. The capacitance of the extended gate is controlled to be very small via the thickness of the insulator layer so that it may be ignored when compared with the gate capacitance of the transistor. As the result, the gate voltage may be fully dependent on the surface charge of the extended gate. The surface immobilization of the monoclonal antibody of microalbumin (mab-MA) on the extended gate is confirmed by the specific binding test of modified Au nanoparticles (NPs), resulting in a high density Au nanoparticles of about 800 NPs/um². When the microalbumin protein of 1 ng/ml on the mab-MA surface of the extended gate is injected, the extremely high sensitivity of 1800% is observed.