MOSFET gas sensor and method of manufacturing the same

Abstract

This application relates to a MOSFET gas sensor, comprising: a substrate made of doped semiconductor material; a semiconductor layer with a channel formed on its surface, wherein a source region is formed at one end of the channel and a drain region is formed at the other end; an insulating dielectric layer located between the substrate and the semiconductor layer for electrically separating the semiconductor and the substrate; a source electrode and a drain electrode respectively disposed in the source region and the drain region; a passivation layer covering the semiconductor layer and a portion of the insulating dielectric layer; and a gas-sensitive layer covering the channel region; wherein a gate region notch is formed on one side of the channel in the semiconductor layer, the gate region notch penetrating the insulating dielectric layer, and a gate electrode is formed on the substrate at the gate region notch. This application effectively improves the sensitivity of the gas sensor.

Description

Technical Field

[0001] This application relates to the field of gas sensors, and more particularly to a MOSFET gas sensor and a method for fabricating the same. Background Technology

[0002] Metal-oxide-semiconductor field-effect transistor (MOSFET) gas sensors are common gas detection and measurement devices. They utilize the interaction between gas and the semiconductor surface to detect and measure gas concentration, and are widely used in environmental monitoring, industrial control, biomedicine, and security fields.

[0003] Currently, common MOSFET gas sensors include:

[0004] The substrate is made of semiconductor material, and the active and drain regions are formed on the substrate;

[0005] The dielectric layer, located above the substrate, is typically made of insulating materials such as silicon oxide (SiO2);

[0006] The gate, located above the dielectric layer, controls the charge distribution and conductivity of the sensor. The sensitivity and operating state of the gas sensor can be adjusted by applying different voltages to the gate.

[0007] The gas-sensitive layer is located above the gate and is directly exposed to the gas environment;

[0008] Source and drain: Used to measure output current. The source and drain form a PN junction with the region on the substrate, thus forming a current path.

[0009] When the target gas comes into contact with the sensor, it undergoes a chemical reaction or adsorption with the gas-sensitive layer. This reaction alters the electrical properties of the gas-sensitive layer, affecting the charge distribution on the gate. This change in charge distribution on the gate affects the electric field distribution between the gate and the gas-sensitive layer, thus altering the relationship between the gate current and the drain current. By measuring the change in current between the source and drain, information about the target gas concentration can be inferred.

[0010] In response to the aforementioned technologies, the inventors provide another novel MOSFET gas sensor that can improve the sensitivity of the gas sensor. Summary of the Invention

[0011] To improve the sensitivity of gas sensors, this application provides a MOSFET gas sensor and its fabrication method.

[0012] On the one hand, the MOSFET gas sensor provided in this application adopts the following technical solution:

[0013] A MOSFET gas sensor, characterized in that it comprises:

[0014] The substrate is a doped semiconductor material;

[0015] A semiconductor layer has a channel on its surface, with a source region at one end of the channel and a drain region at the other end; an insulating dielectric layer is located between the substrate and the semiconductor layer to electrically separate the semiconductor layer and the substrate.

[0016] A passivation layer covers the semiconductor layer and part of the insulating dielectric layer, and the passivation layer has notches in the source and drain regions;

[0017] Source electrode, a metal layer covering the source region;

[0018] Drain electrode, a metal layer covering the drain region;

[0019] The gas-sensitive layer is located above the channel and covers the channel area;

[0020] The passivation layer has a gate region notch on one side of the channel, the gate region notch penetrates the insulating dielectric layer, and the substrate is covered with a metal layer at the gate region notch to form a gate.

[0021] By adopting the above technical solution, the semiconductor layer with the channel located on the insulating dielectric layer does not serve as a substrate compared to the semiconductor layer in the prior art. Therefore, a thinner semiconductor layer can be obtained through the deposition process, thereby reducing the channel dimension, improving transconductance characteristics, reducing subthreshold swing, improving the gate control capability of the MOSFET, and thus improving the sensitivity of the sensor.

[0022] In addition, the channel is not covered by the gate, and the gas-sensitive layer covers the channel. When the target gas reacts chemically or is adsorbed by the sensitive layer, the electrical properties of the sensitive layer change, which in turn directly affects the electric field distribution at the channel and the change in the drain current. At this time, the gate voltage does not change significantly, which allows the sensor to be controlled within the optimal detection pressure range, thereby improving sensitivity.

[0023] Optionally, both the substrate and the semiconductor layer are made of silicon, and the insulating dielectric layer is silicon oxide.

[0024] Optionally, the channel morphology can be straight, triangular, rectangular, hexagonal, or circular, with each channel having a width of 10–500 nm and a length of 50 nm–5 μm.

[0025] Optionally, the semiconductor layer is formed by CVD silicon deposition or SOI fabrication process, and the thickness of the semiconductor layer is 10-200 nm.

[0026] Optionally, the semiconductor layer is fabricated using SOI technology, in which a wafer having a semiconductor layer and an insulating dielectric layer is physically bonded to a wafer having a substrate and an insulating dielectric layer, thereby forming a wafer having a substrate, an insulating dielectric layer, and a semiconductor layer.

[0027] Optionally, the gas-sensitive layer material is a nanofilm or nanoparticle of gold, silver, platinum, silicon oxide, silicon nitride, zinc oxide, titanium oxide, zirconium oxide, aluminum oxide, cerium oxide, tin oxide, indium oxide, tungsten oxide, copper oxide, nickel oxide, cobalt oxide, or manganese oxide.

[0028] Optionally, the gas-sensitive layer material is generated by physical vapor deposition, chemical vapor deposition, sputtering deposition, spin coating, or spraying processes, and the thickness of the gas-sensitive layer is less than 10 nm.

[0029] Optionally, the passivation layer has a channel region notch in the channel region so that the channel region of the semiconductor layer is in direct contact with the gas-sensitive layer.

[0030] The above technical solution allows the detection gas to be brought closer to the channel, thus improving the detection effect.

[0031] On the other hand, this application also provides a method for fabricating a MOSFET gas sensor, which adopts the following technical solution:

[0032] S1: Provides a substrate;

[0033] S2: An insulating dielectric layer is formed on the surface of the substrate;

[0034] S3: A semiconductor layer is disposed on the surface of the insulating dielectric layer;

[0035] S4: A channel is formed on the surface of the semiconductor layer by photolithography dry etching or wet etching process;

[0036] S5: Form a passivation layer on the upper surface of the semiconductor layer and the insulating dielectric layer;

[0037] S6: A notch is formed on the surface of the passivation layer by photolithography, dry etching or wet etching, and is set at the source region, drain region and gate region on one side of the channel. At the same time, the insulating dielectric layer at the notch of the gate region is etched.

[0038] S7: Doping, which involves doping the source, drain, and gate semiconductor layers and the substrate through ion implantation.

[0039] S8: Set the electrode. The source electrode is formed on the surface of the source region of the semiconductor layer through metal physical or chemical deposition, metal etching or metal stripping processes, the drain electrode is formed on the surface of the drain region of the semiconductor layer, and the gate electrode is formed on the substrate surface in the gate region notch.

[0040] S9: Gas-sensitive layer deposition, a thin film of gas-sensitive material is deposited above the channel to form a gas-sensitive layer.

[0041] Optionally, the passivation layer can be etched away between the gas-sensitive layer and the channel to create a gap in the channel area.

[0042] In summary, this application includes at least one of the following beneficial technical effects:

[0043] 1. By reducing the nanowire channel dimension, the transconductance and subthreshold swing characteristics are improved, thereby enhancing the gate control capability of the MOSFET.

[0044] 2. To ensure that the channel can fully contact the object being measured, thereby reflecting the changes in the channel and the object being measured.

[0045] 3. After the gas-sensitive layer comes into contact with the gas, it directly affects the charge distribution at the channel, causing a change in the drain current. This allows the sensor to be controlled within the optimal detection range, thereby improving sensitivity. Attached Figure Description

[0046] Figure 1 This is a schematic diagram illustrating the channel structure in an embodiment of this application.

[0047] Figure 2 yes Figure 1 AA rotating section view.

[0048] Figure 3 This is a schematic diagram illustrating the overall structure of another embodiment of this application.

[0049] Figure 4 This is Example 1 of the present application, used to demonstrate the input-output characteristic curves with and without reactive gases.

[0050] Figure 5 This is a comparative example used in this application to demonstrate the input-output characteristic curves with and without reactive gases.

[0051] Explanation of reference numerals in the attached figures: 100, substrate; 200, insulating dielectric layer; 300, semiconductor layer; 301, channel; 300a, source region; 300b, drain region; 400, passivation layer; 400c, gate region notch; 400d, channel region notch; 501, source; 502, drain; 503, gate; 600, gas-sensitive layer. Detailed Implementation

[0052] The present application will be further described in detail below with reference to the accompanying drawings.

[0053] This application discloses a MOSFET gas sensor, which comprises at least, in sequence, a substrate 100, an insulating dielectric layer 200, a semiconductor layer 300, a passivation layer 400, and a gas-sensitive layer 600.

[0054] The substrate 100 is subjected to high-dose doping through impurity diffusion or ion implantation processes to improve its conductivity.

[0055] The substrate 100 is made of monocrystalline silicon or polycrystalline silicon.

[0056] The insulating dielectric layer 200 is a gate oxide layer formed after silicon oxidation. Alternatively, the insulating layer can be grown on the surface of the substrate 100 using CVD or PVD deposition processes. The thickness of the gate oxide layer ranges from 1 to 500 nm.

[0057] The semiconductor layer 300 is located in the middle of the insulating dielectric layer 200. The area of ​​the semiconductor layer 300 is smaller than the area of ​​the substrate 100. The material of the semiconductor layer 300 is single-crystal silicon. The thickness of the semiconductor layer is 10–200 nm.

[0058] A channel 301 is provided in the middle of the semiconductor layer 300. The shape of the channel 301 can be straight, triangular, rectangular, hexagonal or circular. The width of each channel 301 is 10 to 500 nm and the length is 50 nm to 5 μm.

[0059] The semiconductor layer 300 has an active region 300a at one end of the channel 301 and a drain region 300b at the other end.

[0060] The passivation layer 400 is formed by heating the semiconductor layer 300 to 900 degrees Celsius in an oxygen atmosphere through a thermal oxidation process, and only covers the surface of the semiconductor layer 300; or the passivation layer 400 is formed by a CVD deposition process, and covers the semiconductor layer 300 and part of the surface of the insulating dielectric layer 200.

[0061] The passivation layer 400 forms notches in the source region 300a and drain region 300b using photolithography, dry etching, or wet etching processes. Simultaneously, notches are also formed in the passivation layer 400 located in the channel 301 region and on one side of the channel 301. The notch on the side of the channel 301 is the gate region notch 400c, and the notch formed in the channel 301 region is the channel region notch 400d. Depending on the specific gas being detected, the passivation layer 400 may not have the channel region notch 400d. Specifically, when the charge of the gas atoms attached to the gas-sensitive layer 600 has a sufficiently large impact on the channel 301, the passivation layer below the gas-sensitive layer 600 can be retained, which also reduces process costs. However, if the charge of the gas being detected is weak, it is best for the gas-sensitive layer 600 to be in direct contact with the channel 301.

[0062] Furthermore, the working principle varies depending on the physical characteristics of the gas-sensitive layer 600. If the gas-sensitive layer 600 itself is a good insulating layer, or if the passivation layer 400 is below the gas-sensitive layer 600, the working principle is that gas atoms affect the channel current by changing the MOS capacitance. If the gas-sensitive layer 600 itself is not an insulator and is in direct contact with the channel 301, such as metal nanoparticles, nanofilms, or partially metal oxide films, the working principle is that the charge of gas atoms is directly transferred to the channel 301, affecting the charge distribution within the channel 301.

[0063] Both the source region 300a and the drain region 300b are formed by high-concentration doping of the semiconductor layer 300. By depositing a metal layer, a source electrode 501 is provided on the surface of the semiconductor layer 300 in the source region 300a, and a drain electrode 502 is provided on the surface of the semiconductor layer 300 in the drain region 300b.

[0064] A gate region notch 400c is formed on one side of the passivation layer 400 located on the channel 301, and the gate region notch 400c penetrates the insulating dielectric layer 200 and the passivation layer 400. A metal layer is filled in the gate region notch 400c and forms a gate 503 that electrically contacts the surface of the substrate 100.

[0065] The source 501, drain 502 and gate 503 are all formed by metal CVD or PVD deposition process, photolithography process, metal etching or metal stripping process.

[0066] The source 501, drain 502 and gate 503 are metal electrodes, and the metal electrodes are one or more of Ti, W, Al, Cu, Au and Ag.

[0067] The gas-sensitive layer 600, located above the channel 301, interacts with the target gas and generates a response. The gas-sensitive layer 600 is made of nanofilms or nanoparticles of metal oxides such as silicon oxide, silicon nitride, zinc oxide, titanium oxide, zirconium oxide, aluminum oxide, cerium oxide, tin oxide, indium oxide, tungsten oxide, copper oxide, nickel oxide, cobalt oxide, and manganese oxide. Alternatively, it can be made of nanofilms or nanoparticles of metals such as gold, silver, or platinum.

[0068] The gas-sensitive layer 600 is produced by physical vapor deposition, chemical vapor deposition, sputtering deposition, spin coating or spraying processes, and its thickness is less than 10 nm.

[0069] This application also discloses a method for fabricating a MOSFET gas sensor:

[0070] S1: Provide a substrate 100. The substrate 100 is made of single-crystal silicon and is highly doped by an impurity diffusion process or an ion implantation process to improve the conductivity of the substrate 100.

[0071] S2: An insulating dielectric layer 200 is formed on the surface of the substrate 100. The insulating dielectric layer 200 is a gate oxide layer formed by a thermal oxidation process. The substrate 100 is placed in a high-temperature furnace at a temperature of 900-1000 degrees Celsius, and oxygen or a mixture of oxygen and hydrogen is introduced into the high-temperature furnace to oxidize the surface of the substrate 100 to form a gate oxide layer.

[0072] S3: A semiconductor layer 300 is formed on the surface of the insulating dielectric layer 200. The semiconductor layer 300 can be formed by CVD deposition of silicon, or by SOI fabrication process, in which a wafer with a semiconductor layer 300 and an insulating dielectric layer 200 is physically bonded to a wafer with a substrate 100 and an insulating dielectric layer 200, to form a wafer with a substrate 100, an insulating dielectric layer 200, and a semiconductor layer 300.

[0073] S4: Generate channel 301.

[0074] Channels 301 are formed on the surface of semiconductor layer 300 using photolithography and etching processes. The morphology of channel 301 can be linear, triangular, rectangular-hexagonal, or circular, with each channel 301 having a width of 10–500 nm and a length of 50 nm–5 μm.

[0075] S5: Set passivation layer 400. Passivation layer 400 is formed on the upper surface of semiconductor layer 300 and insulating dielectric layer 200 by deposition process or thermal oxidation process.

[0076] S6: Three notches are formed in the passivation layer 400 using photolithography, dry etching, or wet etching. Two of the notches are located at the two ends of the channel 301, but the semiconductor layer 300 is retained to form the source region 300a and the drain region 300b. The other notch is located in the gate region. At the same time, the insulating dielectric layer 200 at the gate region notch 400c is etched.

[0077] S7: Doping, the semiconductor layer 300 of the source region 300a and drain region 300b and the substrate 100 of the gate region are doped by ion implantation process.

[0078] S8; Setting the electrode. A source electrode 501 is formed on the surface of the semiconductor layer 300 in the source region 300a by means of a metal physical or chemical deposition process, a metal etching process, or a metal stripping process. A drain electrode 502 is formed on the surface of the semiconductor layer 300 in the drain region 300b. A gate electrode 503 is formed on the surface of the substrate 100 in the gate region notch 400c.

[0079] S9: Deposition of gas-sensitive layer 600. A thin film of gas-sensitive material is deposited above channel 301. The thickness of gas-sensitive layer 600 is less than 10 nm.

[0080] The following is a more detailed description in conjunction with Examples 1-9.

[0081] Example 1:

[0082] The MOSFET gas sensor, specifically, is fabricated using the aforementioned process. More specifically, the substrate 100 of this gas sensor is made of single-crystal silicon, and the substrate 100 is highly doped using an impurity diffusion process, with a doping concentration of 1e20cm⁻¹. -3 The above measures are taken to improve the conductivity of substrate 100, and the thickness of the substrate is 500 μm.

[0083] The insulating dielectric layer 200 is a gate oxide layer formed after silicon oxidation. The temperature of the high-temperature furnace is set to 950 degrees Celsius, and the gas is a mixture of oxygen and hydrogen. The thickness of the gate oxide layer is 100 nm.

[0084] The semiconductor layer 300 is made of single-crystal silicon and is formed by CVD deposition of silicon. The reaction gases are SiCl4 and H2, and the thickness of the semiconductor layer is 50 nm.

[0085] The channel 301 has a hexagonal shape, with each channel 301 having a width of 100 nm and a length of 200 nm.

[0086] Both the source electrode 501 and the drain electrode 502 are formed by metal CVD or PVD deposition, photolithography, metal etching or metal lift-off processes.

[0087] The source 501, drain 502, and gate 503 all use Ag as metal electrodes, and the process is evaporation deposition.

[0088] The passivation layer 400 is a SiN4 layer formed by CVD deposition and covering the surface of the semiconductor layer 300.

[0089] The gas-sensitive layer is an Au gas-sensitive layer formed by physical vapor deposition, and its thickness is 1.2 nm.

[0090] Example 2:

[0091] The MOSFET gas sensor differs from Embodiment 1 in that:

[0092] The thickness of substrate 100 is 746 μm;

[0093] The thickness of the gate oxide layer is 100 nm;

[0094] The thickness of semiconductor layer 300 is 50nm;

[0095] The thickness of the gas-sensitive layer 600 is 1.2 nm.

[0096] Example 3:

[0097] The MOSFET gas sensor differs from Embodiment 1 in that:

[0098] The thickness of substrate 100 is 746 μm;

[0099] The thickness of the gate oxide layer is 1.2 nm;

[0100] The thickness of semiconductor layer 300 is 11 nm;

[0101] The thickness of the gas-sensitive layer 600 is 1.1 nm.

[0102] Example 4:

[0103] The MOSFET gas sensor differs from Embodiment 1 in that:

[0104] The thickness of substrate 100 is 56 μm;

[0105] The thickness of the gate oxide layer is 9.1 nm;

[0106] The thickness of semiconductor layer 300 is 13nm;

[0107] The thickness of the gas-sensitive layer 600 is 1.3 nm.

[0108] Example 5:

[0109] The MOSFET gas sensor differs from Embodiment 1 in that:

[0110] The thickness of substrate 100 is 740 μm;

[0111] The thickness of the gate oxide layer is 1.3 nm;

[0112] The thickness of semiconductor layer 300 is 196 nm;

[0113] The thickness of the gas-sensitive layer 600 is 1.1 nm.

[0114] Example 6:

[0115] The MOSFET gas sensor differs from Embodiment 1 in that:

[0116] The thickness of substrate 100 is 52 μm;

[0117] The thickness of the gate oxide layer is 1.2 nm;

[0118] The thickness of semiconductor layer 300 is 12nm;

[0119] The thickness of the gas-sensitive layer 600 is 9.6 nm.

[0120] Example 7:

[0121] The MOSFET gas sensor differs from Embodiment 1 in that:

[0122] The thickness of substrate 100 is 721 μm;

[0123] The thickness of the gate oxide layer is 8.9 nm;

[0124] The thickness of semiconductor layer 300 is 190 nm;

[0125] The thickness of the gas-sensitive layer 600 is 9.2 nm.

[0126] Comparative Example 1:

[0127] The gas sensor includes:

[0128] The substrate is made of silicon, and the active and drain regions are formed on the substrate. The thickness of the substrate is 70 nm. The oxide insulating layer is located on top of the substrate and is made of silicon oxide (SiO2) insulating material with a thickness of 1.1 nm.

[0129] The gate is located above the dielectric layer.

[0130] The gas-sensitive layer is located above the gate and is made of Au with a thickness of 1.1 nm.

[0131] Source and drain: Used to measure output current. The source and drain form a PN junction with a region on the substrate, thus creating a current path. The source and drain are made of the same material as the gate, Ag.

[0132] Table 1: Parameter table for Examples 1-7 and Comparative Examples

[0133]

[0134] Sensitivity test:

[0135] 1. Set up the test platform: Connect the MOSFET gas sensor to the test circuit. The test circuit includes:

[0136] A constant current source, electrically connected to the drain 502 of the MOS tube gas sensor, is used to provide a stable constant current;

[0137] A voltage source, electrically connected to the gate 503 of the MOS tube gas sensor, is capable of providing an adjustable voltage to change the voltage of the gate 503 of the MOS tube. In this application, a digital voltage source is used.

[0138] An oscilloscope is used to measure the source output current of the 501 MOSFET gas sensor.

[0139] Gas supply system: used to control the type and concentration of gas in the test environment. In the embodiments of this application, the gas supply system includes an oxygen pipe, a nitrogen pipe and a test container. The test container is provided with two openings. One opening is connected to a gas mixer. The other end of the mixer is connected to the oxygen pipe and the nitrogen pipe through a tee. The other opening is used as an exhaust port.

[0140] In this circuit, the source 501 of the MOS tube gas sensor is connected to the load resistor, and the other end of the load resistor is grounded.

[0141] 2. Test the input-output characteristic curves of the non-reactive gas environment:

[0142] Place the MOSFET gas sensor inside the test container, then turn on the nitrogen cylinder to purge any existing gas from the container for one minute to ensure a stable environment free from gas interference. Next, set an appropriate constant current and vary the gate voltage, recording the source output current at different gate voltages. Finally, plot the input-output characteristic curve based on the test data.

[0143] 4. Test the input-output characteristic curves of the reaction gas environment:

[0144] Without adjusting the flow rate of the nitrogen tank, turn on the oxygen tank and wait for 1 minute to ensure environmental stability and uniform gas concentration distribution. Change the gate voltage and record the source output current at different gate voltages. Finally, plot the input-output characteristic curve based on the test data.

[0145] 5. Compare the input-output characteristic curves under the two environments:

[0146] The input-output characteristic curves under non-reactive gas and reactive gas environments are compared and analyzed to observe the changing trends and obtain the sensitivity under both reactive and non-reactive gas environments. The maximum horizontal distance between the two characteristic curves is the voltage sensitivity V. th The ratio of the ordinates of the two points with the maximum vertical spacing is the current sensitivity I. Ratio .

[0147] Test data:

[0148] Examples 1-7 and the comparative examples were tested. Figure 4 This is the input-output characteristic curve of Example 1. Figure 5 The input-output characteristic curves are shown for the comparative examples. Example 1 has a voltage sensitivity of 0.15V and a current sensitivity of 12, while the comparative example has a voltage sensitivity of 0.08V and a current sensitivity of 2. Table 2 shows the voltage / current sensitivity of Examples 1-7 and the comparative example. It is clear that the voltage / current sensitivity of this application is superior to that of the comparative example, indicating that it is more sensitive to gas reactions.

[0149] Table 2: Voltage / Current Sensitivity Tables for Examples 1-7 and Comparative Examples

[0150] product Voltage sensitivity / V Current sensitivity Example 1 0.15 12 Example 2 0.2 15 Example 3 0.3 20 Example 4 0.2 1 Example 5 0.3 20 Example 6 0.1 10 Example 7 0.1 5 Comparative Example 0.08 2

[0151] The above are all preferred embodiments of this application, and are not intended to limit the scope of protection of this application. Therefore, all equivalent changes made in accordance with the structure, shape and principle of this application should be covered within the scope of protection of this application.

Claims

1. A MOSFET gas sensor, characterized in that, include: The substrate (100) is a doped semiconductor material; A semiconductor layer (300) has a channel (301) on its surface. A source region (300a) is provided at one end of the channel (301) and a drain region (300b) is provided at the other end of the semiconductor layer (300). An insulating dielectric layer (200) is located between the substrate (100) and the semiconductor layer (300) to electrically separate the semiconductor layer (300) and the substrate (100); A passivation layer (400) covers the semiconductor layer (300) and part of the insulating dielectric layer (200), and the passivation layer (400) has notches in the source region (300a) and the drain region (300b); Source (501), a metal layer covering the source region (300a); Drain (502), a metal layer covering the drain region (300b); A gas-sensitive layer (600) is located above the channel (301) and covers the area of ​​the channel (301); The passivation layer (400) has a gate region notch (400c) on one side of the channel (301), the gate region notch (400c) penetrates the insulating dielectric layer (200), and the substrate (100) is covered with a metal layer at the gate region notch (400c) to form a gate (503); the passivation layer (400) has a channel region notch (400d) in the channel (301) region so that the channel (301) region of the semiconductor layer (300) is in direct contact with the gas-sensitive layer (600).

2. A MOSFET gas sensor according to claim 1, characterized in that: The substrate (100) and the semiconductor layer (300) are both made of silicon material, and the insulating dielectric layer (200) is silicon oxide.

3. A MOSFET gas sensor according to claim 2, characterized in that: The channel (301) has a straight, triangular, rectangular, hexagonal or circular shape, and each channel (301) has a width of 10~500nm and a length of 50nm~5um.

4. A MOSFET gas sensor according to claim 3, characterized in that: The semiconductor layer (300) is formed by CVD silicon deposition process or SOI preparation process, and the thickness of the semiconductor layer (300) is 10~200nm.

5. A MOSFET gas sensor according to claim 4, characterized in that: The semiconductor layer (300) is fabricated using SOI process. A wafer with a semiconductor layer (300) and an insulating dielectric layer (200) is bonded to a wafer with a substrate (100) and an insulating dielectric layer (200) by physical bonding, thereby forming a wafer with a substrate (100), an insulating dielectric layer (200), and a semiconductor layer (300).

6. A MOSFET gas sensor according to claim 1, characterized in that: The gas-sensitive layer (600) material is a nanofilm or nanoparticle of gold, silver, platinum, silicon oxide, silicon nitride, zinc oxide, titanium oxide, zirconium oxide, aluminum oxide, cerium oxide, tin oxide, indium oxide, tungsten oxide, copper oxide, nickel oxide, cobalt oxide, or manganese oxide.

7. A MOSFET gas sensor according to claim 1, characterized in that: The gas-sensitive layer (600) material is generated by physical vapor deposition, chemical vapor deposition, sputtering deposition, spin coating or spraying process, and the thickness of the gas-sensitive layer (600) is less than 10 nm.

8. A method for fabricating a MOSFET gas sensor, applied to the MOSFET gas sensor as described in any one of claims 1-7, characterized in that: S1: Provide substrate (100); S2: An insulating dielectric layer (200) is formed on the surface of the substrate (100); S3: A semiconductor layer (300) is disposed on the surface of the insulating dielectric layer (200); S4: A channel (301) is formed on the surface of the semiconductor layer (300) by photolithography dry etching or wet etching process. S5: Form a passivation layer (400) on the upper surface of the semiconductor layer (300) and the insulating dielectric layer (200). S6: A notch is formed on the surface of the passivation layer (400) by photolithography, dry etching or wet etching, and is set at the source region (300a) and drain region (300b) at both ends of the channel (301) and the gate region on one side of the channel (301). At the same time, the insulating dielectric layer (200) at the gate region notch (400c) is etched. S7: Doping, the source region (300a), the drain region (300b) semiconductor layer (300) and the gate region substrate (100) are doped by ion implantation process; S8: Set electrodes, and form a source (501) on the surface of the source region (300a) of the semiconductor layer (300) by metal physical or chemical deposition process, metal etching or metal stripping process, form a drain (502) on the surface of the drain region (300b) of the semiconductor layer (300), and form a gate (503) on the surface of the substrate (100) in the gate region notch (400c). S9: Gas-sensitive layer (600) deposition, a gas-sensitive material film is deposited above the channel (301) to form a gas-sensitive layer (600).

9. A method for fabricating a MOSFET gas sensor according to claim 8, characterized in that: Between the gas-sensitive layer (600) and the channel (301), the passivation layer (400) is not retained by the etching process to form a gap (400d) in the channel area.

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