Patent ID: 7049645

Claim:
An FET type sensor comprising; an input diode section and a floating diffusion section consisting of a diffusion region reverse to the substrate in conductivity type, formed across a specified interval on the face side of a P type or N type semiconductor substrate, an input gate and an output gate fixed by way of an insulation film, at positions on the substrate surface corresponding to the initial end and terminal end of a conductive channel formed from the input diode section to the floating diffusion section, a sensing section consisting of an ion sensitive film fixed by way of an insulation film, at a position on the substrate surface corresponding to the middle of the channel, a reset gate fixed by way of an insulation film, at a position on the substrate surface continuous to the side remote from the channel in the floating diffusion section, and a reset diode section consisting of a diffusion region reverse to the substrate in conductivity type, formed on the substrate surface at a side remote from the floating diffusion section in the reset gate, wherein a substance reacting or binding with a specimen in the sample in the sensing section or acting as catalyst for reaction of the specimen is fixed in the sensing section, and the electric charge accumulated in the floating diffusion section after resetting of the potential is detected as potential change, depending on the depth of the potential well changed according to the ion density acting on the sensing section and the number of times of seepage from the potential well.