JP2012073103A - Biosensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a differential amplifier type biosensor allowing selection of a transistor having no variation of properties for a differential pair to improve measurement accuracy.SOLUTION: According to this invention, there is provided a biosensor comprising an FET sensor on a substrate and a differential pair consisting of FETs. The FET sensor comprises a first source electrode and a first drain electrode arranged on the substrate, a first semiconductor film in ohmic contact with the first source electrode and the first drain electrode and arranged on the substrate, a first insulator film arranged on the first semiconductor film, a first gate electrode arranged on the first insulator film, and a second insulator film which is arranged with the first insulator film interposed between the first source electrode/the first drain electrode and the second insulator film, and on which an object to be measured is placed. To the first gate electrode, a voltage is applied during measurement of a difference between a threshold value voltage property of the FET sensor and a threshold value voltage property of the FETs.

Description

  The present invention relates to a biosensor, and more particularly to a biosensor using a field effect transistor.

  Biosensors using electrochemical detection means have been put to practical use as methods for quickly and simply measuring concentrations and the like of biological samples such as blood and cells and specific components therein. As one of them, a biosensor using a field effect transistor (hereinafter referred to as an FET) is known, and is particularly called an ISFET (Ion-sensitive FET). The application of ISFETs to detection systems for biological components such as DNA and proteins, and cells has been actively studied.

  In recent years, a biosensor has been developed in which a transistor used in a biosensor has a differential pair configuration, and one of the differential pairs is an ISFET (for example, Patent Document 1). In a biosensor using one of the differential pairs as an ISFET, a signal can be extracted with the change in the ISFET as a voltage difference from a certain reference voltage, and a small change in the ISFET is amplified by setting the amplification level of the differential pair. It becomes possible.

  In order to extract a signal by using a change in ISFET as a voltage difference from a reference voltage, or to amplify a minute change in ISFET, it is not preferable that there is a variation in transistor characteristics between differential pairs. If there are variations in the transistor characteristics of the differential pair, the signal may shift as an offset of the differential characteristics, but the shift amount is close to the change amount of the ISFET. There is a problem that the measurement accuracy is low because it cannot be distinguished.

Japanese Patent No. 4063770

  Accordingly, an object of the present invention is to increase measurement accuracy in a differential amplifier type biosensor.

  As one embodiment of the present invention, a biosensor configured by a FET sensor on a substrate and a differential pair comprising FETs, the FET sensor comprising: a first source electrode disposed on the substrate; A first drain electrode; a first semiconductor film disposed on the substrate in ohmic contact with the first source electrode and the first drain electrode; and disposed on the first semiconductor film. A first insulating film, a first gate electrode disposed on the first insulating film, and an overlapping portion of the first semiconductor film and the first gate electrode; A second insulating film disposed on the substrate; the second source electrode and the second drain electrode; and the second source electrode and the second drain. Placed on the substrate in ohmic contact with the electrode A second semiconductor film, and a second gate electrode disposed on the second semiconductor film, and a voltage is applied to the first gate electrode when measuring characteristics of the FET sensor and the FET. A biosensor is provided.

  Further, as one embodiment of the present invention, a biosensor configured by a FET sensor on a base material and a differential pair consisting of FETs, the FET sensor includes a first gate electrode on the base material, A first semiconductor film disposed on the first gate electrode via a first insulating film, and a first source electrode and a first drain disposed in ohmic contact with the first semiconductor film An FET, and a second insulating film that is disposed in an overlapping portion of the first gate electrode and the first semiconductor film, and on which the object to be measured is disposed. A gate electrode, a second semiconductor film disposed on the second gate electrode, a second source electrode and a second drain electrode disposed in ohmic contact with the second semiconductor film, The first gate electrode includes the FET sensor A voltage is applied during characteristic measurement of the fine the FET, the biosensor, which is a floating state during characteristic measurement of the object to be measured is provided.

  In the biosensor according to an embodiment of the present invention, the FET sensor includes a reference electrode that is insulated from the first source electrode and the first drain electrode and applies a variable voltage to the object to be measured. May be.

  The biosensor according to an embodiment of the present invention may include a current mirror circuit and a differential amplifier circuit that amplify a change in voltage measured by the FET sensor.

  The biosensor according to an embodiment of the present invention may include an amplification stage that amplifies a change in voltage measured by the FET sensor.

  In the biosensor according to the embodiment of the present invention, one of the first semiconductor film, the second semiconductor film, the first source electrode, the first drain electrode, and the first gate electrode. The above may be transparent.

  In the biosensor according to one embodiment of the present invention, a hydrophilic region having hydrophilicity may be provided on the second insulating film.

  In the biosensor according to the embodiment of the present invention, the second insulating film may be an ion sensitive film.

  As another embodiment of the present invention, the biosensor according to one embodiment of the present invention, the FET sensor electrically connected to the biosensor according to one embodiment of the present invention, and for measuring the characteristics of the FET And a measuring device for measuring an object electrically connected to the biosensor according to one embodiment of the present invention.

  According to the present invention, for transistors constituting a differential pair, a transistor having no variation in characteristics is selected, a differential pair is configured using a transistor having no variation in the selected characteristics, and the sensor is used as a biosensor. Measurement accuracy can be increased.

(A) is sectional drawing of the biosensor 100 which concerns on one Embodiment of this invention, (b) is the top view. (A) is a figure which shows an example of the wiring pattern of the biosensor 200 which concerns on other embodiment of this invention, (b) is sectional drawing along AA 'of (a), (c) FIG. 4 is a cross-sectional view taken along line BB ′ in FIG. (A) is a circuit diagram of biosensor 100 and 200 concerning one embodiment of the present invention, and (b) is a figure showing a wiring pattern. It is a circuit diagram which shows an example of the circuit which used the biosensor which concerns on one Embodiment of this invention as a current mirror structure, and was set as the differential amplifier type | mold biosensor. It is a graph which shows the relationship between the input voltage at the time of selecting a transistor using the circuit of FIG. 4, and an output current. It is a circuit diagram which shows an example of the circuit which provided the amplification stage in the biosensor which concerns on one Embodiment of this invention. It is a figure which shows the example of the measuring apparatus using the biosensor which concerns on one Embodiment of this invention.

  Hereinafter, a biosensor and a manufacturing method thereof according to the present invention will be described with reference to the drawings. However, the biosensor of the present invention can be implemented in many different modes and should not be construed as being limited to the description of the embodiments and examples shown below. Note that in the drawings referred to in this embodiment mode and examples, the same portions or portions having similar functions are denoted by the same reference numerals, and repetitive description thereof is omitted.

  FIG. 1 is a cross-sectional view of a biosensor 100 according to an embodiment of the present invention.

  The biosensor 100 according to the present embodiment includes an FET sensor 100a and an FET 100b on the upper surface, which is an element formation surface of the base material 101. The FET sensor 100a includes a first semiconductor film 131a, a first drain electrode 113a, a first source electrode 115a, a first gate electrode 111a, a first insulating film 141, and a second insulating film 151. The FET 100b includes a second semiconductor film 131b, a second drain electrode 113b, a second source electrode 115b, a second gate electrode 111b, and a first insulating film 141. In the biosensor 100, the partition 161 may be further formed on the first insulating film 141 in order to dispose the measurement object 191 on the first insulating film 141 and the second insulating film 151.

  The base material 101 is an insulating material. For example, inorganic materials such as glass, plastics such as PEN or PET (polyester resin, polyethylene resin, polypropylene resin, ABS resin, nylon, acrylic resin, fluororesin, polycarbonate resin, polyurethane resin, methylpentene resin, phenol resin, melamine Resin, epoxy resin, vinyl chloride resin) may be used. The substrate 101 is preferably transparent. The transparent means only needs to be transparent to the extent that the object to be measured 191 disposed on the second insulating film 151 can be observed from the substrate 101 using an observation device such as a microscope, and is translucent. Is not included.

  In addition, the shape of the substrate 101 is not particularly limited, and it is a flat shape such as a flat plate, a flat membrane, a film, and a porous membrane, and a three-dimensional shape such as a cylinder, a stamp, a multiwell plate, and a microchannel. There may be. In the case of using a film, the thickness is not particularly limited, but may be, for example, 1 μm or more and 1 mm or less.

  When the base material 101 is a flexible material, the base material 101 can be bent, and the degree of freedom such as installation of an FET sensor during measurement increases. In addition, the biosensor can be formed by roll-to-roll, and the biosensor can be manufactured at a low cost.

  Note that another insulating film may be disposed and formed over the substrate 101. In this case, the FET sensor is formed on another insulating film on the substrate 101. When the substrate 101 has conductivity, the current flowing through the substrate 101 can be reduced. In this case, the other insulating film material is preferably transparent.

  Hereinafter, the configuration of the FET sensor 100a will be described.

  The first source electrode 115 a and the first drain electrode 113 a are disposed on the base material 101.

  A conductive material is used for the first drain electrode 113a and the first source electrode 115a. For example, titanium, aluminum, copper, gold, or the like can be used, but it is particularly preferable to use a transparent conductive material, for example, indium tin oxide (ITO), zinc oxide (ZnO), indium zinc oxide (IZO). Alternatively, zinc oxide (GZO) to which gallium is added can be used. The thickness of the first drain electrode 113a and the first source electrode 115a is preferably 20 nm to 200 nm.

  The first semiconductor film 131 a is disposed on the base material 101. In addition, the first semiconductor film 131a is disposed between the first source electrode 115a and the first drain electrode 113a. The first semiconductor film 131a is in ohmic contact with the first source electrode 115a and the first drain electrode 113a.

  As a material of the first semiconductor film 131a, any material can be used as long as the first insulating film 141 can be stacked. For example, an amorphous oxide can be used. The main component of such an amorphous oxide can be expressed as InMZnO, where M is at least one of Ga (gallium), Al (aluminum), and Fe (iron). Among these, as the amorphous oxide, it is preferable to use an InGaZnO-based material in which M is Ga. Since an InGaZnO-based amorphous oxide can be formed at room temperature to a low temperature of about 150 ° C., it can be used even when the substrate 101 is made of plastic or glass having poor heat resistance. In addition, Al, Fe, Sn, or the like may be added to the InGaZnO-based amorphous oxide as necessary.

  Another material of the first semiconductor film 131a may be an oxide semiconductor containing zinc oxide (ZnO) as a main component. When ZnO is the main component, in addition to intrinsic oxide zinc, p-type dopants such as lithium (Li), sodium (Na), nitrogen (N) and carbon (C), and boron, if necessary (B), zinc oxide doped with n-type dopants such as aluminum (Al), gallium (Ga), indium (In), and zinc oxide doped with magnesium (Mg), beryllium (Be), etc. It may be. Further, the first semiconductor film 131 may be formed of an oxide semiconductor such as indium oxide to which tin is added (indium tin oxide: ITO), indium zinc oxide (IZO), or magnesium oxide (MgO).

  The first semiconductor film 131 is preferably transparent. This transparent means that, as with the substrate 101, it is transparent to the extent that the object 191 placed on the second insulating film 151 can be observed from the substrate 101 using an observation device such as a microscope. Well, translucent ones are not included.

  The first insulating film 141 is stacked over the first source electrode 115a, the first drain electrode 113a, and the first semiconductor film 131a.

  An insulating material is used for the first insulating film 141, and it is particularly preferable to use a transparent insulating material. For example, silicon oxide, silicon nitride, silicon oxynitride, or the like can be used. Further, a substrate made of a transparent organic resin such as a plastic substrate, a transparent film such as polypropylene, polyester, vinyl, polyvinyl fluoride, vinyl chloride, polyester, and polyamide may be used. The thickness of the first insulating film 141 can be appropriately selected within a range of 50 nm to 1 μm. Note that this transparent is transparent to the extent that the object to be measured 191 placed on the second insulating film 151 can be observed from the base 101 using an observation device such as a microscope, as with the base 101. It only has to be, and translucent ones are not included.

  The second insulating film 151 is in contact with the first insulating film 141 and is disposed above the overlapping portion of the first semiconductor film 131a and the first gate electrode 111a. In addition, the second insulating film 151 is disposed in contact with the first semiconductor film 131a indirectly through the first insulating film 141. For example, the second insulating film 151 may be disposed so as to cover the first insulating film 141. The second insulating film 151 can arrange an object to be detected, for example, a cell, DNA, sugar chain, protein, or the like included in the sample added to the object to be measured 191. The ion sensitive layer 151 is made of a transparent insulating material such as silicon oxide, silicon nitride, silicon oxynitride, tantalum oxide, or aluminum oxide.

  The first gate electrode 111 a is disposed between the first insulating film 141 and the second insulating film 151. A conductive material is used for the first gate electrode 111a. For example, titanium, aluminum, copper, gold, or the like can be used, but it is particularly preferable to use a transparent conductive material, for example, indium tin oxide (ITO), zinc oxide (ZnO), indium zinc oxide (IZO). Alternatively, zinc oxide (GZO) to which gallium is added can be used. The thickness of the first gate electrode 111a, the first drain electrode 113a, and the first source electrode 115a is preferably 20 nm to 200 nm.

  In addition, the first gate electrode 111a can be used as a floating electrode when measuring the characteristics of an object to be measured by a biosensor.

  If the electrode material of the first gate electrode 111a, the first drain electrode 113a, and the first source electrode 115a is transparent, the sample can be more reliably observed with a microscope. Depending on the location, it is preferred that one or more of the electrode materials of these electrodes is transparent. This transparent means that, as with the substrate 101, it is transparent to the extent that the object 191 placed on the second insulating film 151 can be observed from the substrate 101 using an observation device such as a microscope. Well, translucent ones are not included.

  The partition wall 161 is for placing the object to be measured 191, and for example, glass, plastic or the like can be used. In FIG. 1B, the partition wall 161 is square when viewed from above, but is not limited thereto, and may be, for example, circular.

  The biosensor 100 according to the embodiment of the present invention is output from the device under test 191 by bringing the reference electrode 117 insulated from the first drain electrode 113a and the first source electrode 115a into contact with the device under test 191. An electrical signal may be measured. The reference electrode 117 may be inserted into the object to be measured 191 or may be formed as a pattern.

  Next, the configuration of the FET 101b will be described. The second source electrode 115 b and the second drain electrode 113 b are disposed on the base material 101. The second semiconductor film 131 b is disposed on the base material 101. In addition, the second semiconductor film 131b is disposed between the second source electrode 115b and the second drain electrode 113b. The second semiconductor film 131b is in ohmic contact with the second source electrode 115b and the first drain electrode 113b. The first insulating film 141 is also stacked over the second source electrode 115b, the second drain electrode 113b, and the second semiconductor film 131b. A second gate electrode 111b is disposed on the first insulating film 141.

  Regarding the materials used for the second source electrode 115b, the second drain electrode 113b, the second semiconductor film 131b, and the second gate electrode 111b constituting the FET 100b, the first source electrode 115a and the first drain electrode are used. The description is omitted because it is similar to the electrode 113a, the first semiconductor film 131a, and the first gate electrode 111a.

  The arrangement of the first and second drain electrodes 113a, b and the first and second source electrodes 115a, b of the FET sensor 100a and FET 100b is an example, and in FIG. 1, the first source electrode 115a is shown. And the second drain electrode 113b are integrally formed. However, the present invention is not limited to this, and for example, the first source electrode 115a and the second source electrode 115b of the FET sensor 100a and the FET 100b may be disposed adjacent to each other. Alternatively, they may be arranged separately without being integrally formed.

  2A is a diagram showing a wiring pattern of a biosensor 200 according to another embodiment of the present invention, and FIG. 2B is a cross-sectional view taken along line AA ′ in FIG. 2 (c) is a cross-sectional view taken along the line BB 'in FIG. 2 (a). By using the first gate electrode 111a as a floating electrode, the first gate electrode 111a is extended, and the second insulating film 151 is moved to a place not directly above the first semiconductor film 131a. Can be freely arranged. Moreover, in the biosensor 200 according to another embodiment of the present invention, the first semiconductor film 131a and the first gate electrode 111a can be made transparent so that the object to be measured can be observed with a microscope or the like. Become.

  Since the characteristics of the material used for the FET sensor 200a and the FET 200b of the biosensor 200 are the same as those of the biosensor 100 described above, description thereof is omitted.

Here, a circuit configuration of the biosensor according to the embodiment of the present invention will be described with reference to FIG. FIG. 3A is a circuit diagram of biosensors 100 and 200 according to an embodiment of the present invention, and FIG. 3B is a diagram showing a wiring pattern.
The biosensor 100 and the biosensor 200 according to an embodiment of the present invention include a transistor selection electrode 180 as shown in FIG. The first gate electrode 111a of the FET sensor 100a is used as the transistor selection electrode 180, and is selectively connected to the reference electrode 117 to the FET sensors 100a and 200a. With this configuration, before measuring the characteristics of the object 191 to be measured, the transistor selection electrodes 180 are used to measure the characteristics of the transistors used as the FET sensors 100a and 200a and the FETs 100b and 200b that constitute the differential pair. Transistors can be selected in advance of sensing by a sensor. Thereby, it is possible to perform highly accurate measurement using a biosensor in which a differential pair is configured by transistors without variation.

  In addition, as described above, the gate electrode 111a used for transistor selection may be used as a floating electrode when sensing with a biosensor.

  As shown in the circuit diagram of FIG. 4, a current mirror circuit 410 may be added to the biosensor according to an embodiment of the present invention, and an amplifier circuit 400 may be provided to provide a differential amplifier type biosensor. As a result, changes in the FET sensors 100a and 200a can be output as voltage signals, and the output voltage signals can be amplified to measure minute voltage changes, so that minute changes in the device under test 191 can be measured. Can be measured.

  Here, an example of the transistor selection operation in the differential amplifier type biosensor of FIG. 4 will be described with reference to FIG.

  In the differential amplifier biosensor of FIG. 4, when an input signal is sent from the transistor selection electrode 180, it is output from Q. Transistor elements that do not vary in threshold voltage characteristics (difference in threshold voltage characteristics) in which the transistor elements constituting the differential pair do not cause an offset when a voltage of 0 to Vdd is sequentially applied to the transistor selection electrode 180 In this case, as shown by the curve m, the output current changes abruptly around Vdd / 2. On the other hand, in the case of a transistor element having a variation in threshold voltage characteristics, an offset occurs, and as shown by the curve n, the point where the output current changes abruptly is different from Vdd / 2. Therefore, it is possible to determine whether or not the threshold voltage characteristics of the transistor elements are varied depending on whether or not the output current changes when the voltage of Vdd / 2 is applied. Is possible.

Furthermore, as shown in the circuit diagram of FIG. 6, the biosensor according to the embodiment of the present invention may be provided with amplification stages 500a and 500b in addition to the amplifier 400 shown in FIG.
Thereby, it becomes possible to further amplify the voltage signal output by the FET sensors 100a and 200a, and it becomes easier to confirm the change of the signal.

  The biosensor according to the embodiment of the present invention may include an affinity layer 171 (not shown) on the second insulating film 106.

  The affinity layer 171 provides the second insulating film 151 with affinity for the measurement object 191 and improves the detection efficiency of the second insulating film 151. In order to provide affinity for the measurement object 191, the affinity layer 171 has hydrophilicity, for example. The affinity layer 171 can be formed of a hydrophilic polymer, and can also be formed by chemically modifying the ion sensitive layer 151 with a hydrophilic functional group. Further, the affinity layer 171 may be formed using a transparent material having a binding property to an object to be detected. The material of the affinity layer 171 can be appropriately set in consideration of the binding characteristics with the object to be detected. Conversely, without forming the affinity layer 171, a hydrophobic material is used for the first insulating film 141 other than the second insulating film 151, and a hydrophobic material is not used for the second insulating film 151, A hydrophobic film may be formed on the upper surface of the first insulating film 141. For example, the first insulating film 141 may be coated with silicone. Alternatively, the first insulating film 141 may be formed using a material having binding inhibition characteristics with respect to an object to be detected, for example, cell adhesion inhibition characteristics.

  As the material of the affinity layer 171, for example, a water-soluble polymer, a water-soluble oligomer, a water-soluble organic compound, a surfactant, an amphiphilic substance, or the like can be used. Water-soluble polymer materials include polyalkylene glycol and derivatives thereof, polyacrylic acid and derivatives thereof, polymethacrylic acid and derivatives thereof, polyacrylamide and derivatives thereof, polyvinyl alcohol and derivatives thereof, zwitterionic polymers, polysaccharides , Etc. Examples of the molecular shape include a straight chain, a branched one, and a dendrimer. Specifically, polyethylene glycol, a copolymer of polyethylene glycol and polypropylene glycol, such as Plonic F108, Plonic F127, poly (N-isopropylacrylamide), poly (N-vinyl-2-pyrrolidone), poly (2-hydroxy). Ethyl methacrylate), poly (methacryloyloxyethylphosphorylcholine), copolymers of methacryloyloxyethylphosphorylcholine and acrylic monomers, dextran, and heparin, but are not limited thereto. Examples of water-soluble oligomer materials and water-soluble low-molecular compounds include alkylene glycol oligomers and derivatives thereof, acrylic acid oligomers and derivatives thereof, methacrylic acid oligomers and derivatives thereof, acrylamide oligomers and derivatives thereof, saponified vinyl acetate oligomers and derivatives thereof, Examples include oligomers composed of zwitterionic monomers and derivatives thereof, acrylic acid and derivatives thereof, methacrylic acid and derivatives thereof, acrylamide and derivatives thereof, zwitterionic compounds, water-soluble silane coupling agents, and water-soluble thiol compounds. . Specifically, ethylene glycol oligomer, (N-isopropylacrylamide) oligomer, methacryloyloxyethylphosphorylcholine oligomer, low molecular weight dextran, low molecular weight heparin, oligoethylene glycol thiol, ethylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol , 2- [methoxy (polyethyleneoxy) -propyltrimethoxysilane, and triethyleneglycol-terminated-thiol, but are not limited thereto.

  The average thickness of the affinity layer 171 is preferably 0.8 nm to 500 μm, more preferably 0.8 nm to 100 μm, more preferably 1 nm to 10 μm, and most preferably 1.5 nm to 1 μm. An average thickness of 0.8 nm or more is preferable because it is difficult to be affected by a region not covered with the affinity layer 171 in protein adsorption or cell adhesion. Moreover, if the average thickness is 500 μm or less, coating is relatively easy. The shape and area of the affinity layer 171 can be appropriately set in consideration of the area and properties of the object to be measured 191 to be arranged. For example, when the object to be measured is a cell, it is possible to measure from only one cell by setting the size of the recess of the affinity layer 171 to a size that allows one cell to be arranged.

  Although not shown, the affinity layer 171 according to the present embodiment is also applicable to the biosensor 200. That is, the affinity layer 171 may be formed on the upper surface of the second insulating film 151.

  In the biosensor according to the present embodiment, it is possible to selectively install the object to be measured on the ion sensitive layer by providing the second insulating film with affinity for the object to be detected by the affinity layer. High-precision measurement is possible.

  With reference to FIG. 7, an example of the measuring apparatus using the biosensor which concerns on one Embodiment of this invention is shown.

  As shown in FIG. 7, the biosensor described using the biosensor 100 or the biosensor 200 as an example is used as an apparatus for transistor selection and an apparatus for measuring characteristics of an object to be measured by connecting to an external measurement apparatus. Can do.

  That is, as shown in FIG. 7, when a transistor used as an FET sensor or FET is selected, a biosensor having a current mirror configuration is connected to the measurement apparatus 1000. The measuring apparatus 1000 can be used as a measuring apparatus for measuring transistor characteristics when selecting transistor elements. Further, when measuring the characteristics of an object to be measured by a biosensor, it can be used as an apparatus for measuring characteristics of the object to be measured. By providing the measuring device outside the biosensor with most of the circuit for characteristic measurement, the circuit of the biosensor itself is simplified, the mass production of the biosensor is facilitated, and the cost for manufacturing the biosensor is reduced. Reduced.

As described above, the biosensor according to the present invention selects transistors having no characteristic variation in the differential pair, and uses the transistors having no characteristic variation as a differential amplifier type biosensor to increase measurement accuracy. I can do it.

100 biosensor 100a FET sensor 100b FET
101 base material 111a first gate electrode 111b second gate electrode 113a first drain electrode 113b second drain electrode 115a first source electrode 115b second source electrode 117 reference electrode 131a first semiconductor film 131b first Two semiconductor films 141 First insulating film 151 Second insulating film 161 Bulkhead 180 Transistor selection electrode 191 Device 200 Biosensor 200a FET sensor 200b FET

Claims (10)

A biosensor constituted by a differential pair consisting of an FET sensor and an FET on a substrate,
The FET sensor is
A first source electrode and a first drain electrode disposed on the substrate;
A first semiconductor film disposed on the substrate in ohmic contact with the first source electrode and the first drain electrode;
A first insulating film disposed on the first semiconductor film;
A first gate electrode disposed on the first insulating film;
A second insulating film disposed in an overlapping portion of the first semiconductor film and the first gate electrode, and a device under test being disposed;
With
The FET is
A second source electrode and a second drain electrode disposed on the substrate;
A second semiconductor film disposed on the substrate in ohmic contact with the second source electrode and the second drain electrode;
A second gate electrode disposed on the second semiconductor film;
With
The biosensor according to claim 1, wherein a voltage is applied to the first gate electrode when measuring a difference between a threshold voltage characteristic of the FET sensor and a threshold voltage characteristic of the FET. A biosensor constituted by a differential pair consisting of an FET sensor and an FET on a substrate,
The FET sensor is
A first gate electrode on the substrate;
A first semiconductor film disposed on the first gate electrode via a first insulating film;
A first source electrode and a first drain electrode disposed in ohmic contact with the first semiconductor film;
A second insulating film that is disposed in an overlapping portion of the first gate electrode and the first semiconductor film and in which a device under test is disposed;
With
The FET is
A second gate electrode on the substrate;
A second semiconductor film disposed on the second gate electrode;
A second source electrode and a second drain electrode disposed in ohmic contact with the second semiconductor film;
With
A voltage is applied to the first gate electrode when measuring a difference between a threshold voltage characteristic of the FET sensor and a threshold voltage characteristic of the FET, and the first gate electrode is in a floating state when measuring an object to be measured. A biosensor. 3. The FET sensor according to claim 1, further comprising a reference electrode that is insulated from the first source electrode and the first drain electrode and applies a variable voltage to the object to be measured. The biosensor according to crab. The biosensor according to any one of claims 1 to 3, further comprising a current mirror circuit and a differential amplifier circuit for amplifying a change in voltage measured by the FET sensor. The biosensor according to claim 4, further comprising an amplification stage that amplifies a change in voltage measured by the FET sensor. The one or more of the first semiconductor film, the second semiconductor film, the first source electrode, the first drain electrode, and the first gate electrode are transparent. The biosensor according to any one of 1 to 5. The biosensor according to claim 1, wherein a hydrophilic region having hydrophilicity is provided on the second insulating film. The biosensor according to any one of claims 1 to 7, further comprising a partition wall arranged around the measurement object in the second insulating film. The biosensor according to claim 1, wherein the second insulating film is an ion-sensitive film. The biosensor according to any one of claims 1 to 9,
The FET sensor electrically connected to the biosensor according to any one of claims 1 to 9 and a measurement device for measuring the characteristics of the FET,
A biosensor device comprising: a measuring device for measuring an object electrically connected to the biosensor according to any one of claims 1 to 9.