Gate structure of GaN-based power device and manufacturing method thereof

Abstract

The present invention discloses a gate structure of a GaN-based power device and a manufacturing method thereof. The gate structure includes a dielectric layer, a first transition layer, a second transition layer and a stacked gate electrode layer arranged in sequence, and one or more work function layers are arranged between the first transition layer and the second transition layer, and the work function layer includes a basic material layer, and one or more windows are arranged on the basic material layer, and the windows are filled with a composite material, and the composite material is at least formed by a composite of a basic material forming the basic material layer and a work function regulating material; the basic material is selected from a metal compound, and the work function regulating material is selected from a metal material. The layered distribution and / or graphical distribution control of the work function regulating material elements in the work function layer of the gate structure of the GaN-based power device provided by the embodiment of the present invention can effectively modulate the current and electric field density distribution in the gate region of the GaN-based power device, solve the adverse effects brought by the introduction of the work function layer, enable the device to reach thermal equilibrium, and improve the breakdown voltage of the device.

Description

Technical Field

[0001] The present invention particularly relates to a gate structure of a GaN-based power device and a manufacturing method thereof, and belongs to the technical field of microelectronics. Background Art

[0002] Power electronics is the core of human industrial production activities. Therefore, how to develop power electronics technology with higher efficiency and lower loss is of vital importance to solving the global energy crisis and building a green ecology. Among the current solutions for power electronic energy conversion / transmission, the use of new power semiconductor devices with excellent performance is considered to be a good solution to achieve this ultimate goal of mankind. Wide bandgap compound semiconductor materials represented by gallium nitride are gaining more and more attention due to their device properties far superior to those of traditional silicon materials. Gallium nitride-based AlGaN / GaN HEMTs (High Mobility Electron Transistors) power devices have become a milestone representative of wide bandgap compound semiconductor devices in the application of high-speed, high-frequency and high-efficiency occasions due to their easy-to-implement heterojunction, high-concentration two-dimensional electron gas (2DEG), high channel electron mobility, high breakdown electric field and relatively simple manufacturing process.

[0003] In the field of high-voltage and high-performance GaN-based power devices, the gate of the device often adopts a MOS structure and the threshold voltage needs to be more accurately controlled, while the traditional MOS structure gate is composed of a dielectric layer and a stacked gate electrode layer and cannot achieve better adjustment of the threshold voltage. The MOS gate structure that introduces a work function layer often has an adverse effect on the electric field and current distribution in the gate area of ​​the GaN-based power device, reducing the gate breakdown voltage and causing thermal mismatch in the gate area, which is unacceptable for power devices that pursue high voltage, high current, and high frequency. Summary of the invention

[0004] The main purpose of the present invention is to provide a gate structure of a GaN-based power device and a method for manufacturing the same, so that during the gate manufacturing process, not only the threshold voltage of the device can be adjusted more accurately, but also the gate region current and electric field density distribution of the GaN-based power device can be effectively modulated, so that the device reaches thermal equilibrium and the breakdown voltage of the device is improved, so as to overcome the shortcomings of the prior art.

[0005] In order to achieve the above-mentioned invention object, the technical solution adopted by the present invention includes:

[0006] An embodiment of the present invention provides a gate structure of a GaN-based power device, comprising a dielectric layer, a first transition layer, a second transition layer and a stacked gate electrode layer arranged in sequence, and one or more work function layers are arranged between the first transition layer and the second transition layer, the work function layer comprises a basic material layer, one or more windows are arranged on the basic material layer, the windows are filled with a composite material, the composite material is at least composed of a basic material forming the basic material layer and a work function regulating material; the material of the first transition layer and the second transition layer is the same as that of the basic material layer, wherein the basic material is selected from metal compounds, and the work function regulating material is selected from metal materials.

[0007] The embodiment of the present invention further provides a method for manufacturing a GaN-based power device gate structure, which comprises:

[0008] The step of forming a dielectric layer; and the step of sequentially forming a first transition layer, one or more work function layers, a second transition layer and a stacked gate electrode layer on the dielectric layer;

[0009] The work function layer includes a basic material layer and a composite material filled in the basic material layer, wherein the composite material is at least composed of a basic material forming the basic material layer and a work function adjustment material; the first transition layer and the second transition layer are formed of the same material as the basic material layer, wherein the basic material is selected from metal compounds, and the work function adjustment material is selected from metal materials.

[0010] An embodiment of the present invention further provides a GaN-based power device, which includes the gate structure of the GaN-based power device, and the gate structure is arranged on the substrate structure of the GaN-based power device.

[0011] Compared with the prior art, the gate structure of a GaN-based power device and the manufacturing method thereof provided by the embodiment of the present invention, the layered distribution and / or graphical distribution control of the work function regulating material elements in the work function layer can effectively modulate the gate region current and electric field density distribution of the GaN-based power device, solve the adverse effects brought by the introduction of the work function layer, enable the device to reach thermal equilibrium, and improve the breakdown voltage of the device; the first transition layer and the second transition layer use a metal compound material consistent with the basic material layer of the work function layer, and by gradually changing the element ratio of the material, the first transition layer and the second transition layer play a role of blocking, protecting and adhering to the work function layer, and the work function layer is placed intact between the dielectric layer and the stacked gate electrode layer without interfering with each other, thereby increasing the reliability of the device. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1 It is a schematic structural diagram of a GaN-based power device in a typical implementation case of the present invention;

[0013] Figure 2 It is a schematic diagram of the structure of the first transition layer in Example 1 of the present invention.

[0014] Figure 3 This is a schematic diagram of the device structure of the basic material layer forming the work function layer in Example 1 of the present invention;

[0015] Figure 4 is a flow chart of a process for controlling the layered distribution of regulating materials in a work function layer according to Example 1 of the present invention;

[0016] Figure 5 is a flow chart of a process for controlling the graphical distribution of the regulating material of the work function layer in Example 1 of the present invention;

[0017] Figure 6 is a schematic structural diagram of the second transition layer in Example 1 of the present invention;

[0018] Figure 7 is a comparison diagram of the thermal distribution of the work function layer formed before and after being processed by the layered distribution control process in Example 1 of the present invention;

[0019] Figure 8 It is a comparison diagram of the electric field density of the work function layer formed before and after the graphic distribution control process in Example 1 of the present invention. DETAILED DESCRIPTION

[0020] In view of the deficiencies in the prior art, the inventor of this case has proposed the technical solution of the present invention after long-term research and extensive practice. The technical solution, its implementation process and principle will be further explained as follows.

[0021] An embodiment of the present invention provides a gate structure of a GaN-based power device, comprising a dielectric layer, a first transition layer, a second transition layer and a stacked gate electrode layer arranged in sequence, and one or more work function layers are arranged between the first transition layer and the second transition layer, the work function layer comprises a basic material layer, one or more windows are arranged on the basic material layer, the windows are filled with a composite material, the composite material is at least composed of a basic material forming the basic material layer and a work function regulating material; the material of the first transition layer and the second transition layer is the same as that of the basic material layer, wherein the basic material is selected from metal compounds, and the work function regulating material is selected from metal materials.

[0022] In some more specific embodiments, the window has a stepped structure.

[0023] In some more specific implementation schemes, a plurality of windows are provided on the base material layer, and the plurality of windows form a set graphic structure.

[0024] Furthermore, the depth of the window is smaller than the thickness of the base material layer.

[0025] In some more specific embodiments, the gate structure of the GaN-based power device includes: more than two work function layers, more than two work function layers are stacked in sequence, and the number, shape and depth of windows on the base material layers of two adjacent work function layers are the same or different.

[0026] Preferably, the number, shape and depth of the windows on the base material layers of two adjacent work function layers are different.

[0027] In some more specific embodiments, the content ratio of the metal element to the non-metal element in any one of the first transition layer and the second transition layer changes in a uniform gradient along a set direction.

[0028] Furthermore, the content ratio of metal elements to non-metal elements in the first transition layer gradually decreases in the direction away from the work function layer, and the maximum content ratio of metal elements to non-metal elements in the first transition layer is consistent with the content ratio of metal elements to non-metal elements in the adjacent basic material layer; the content ratio of metal elements to non-metal elements in the second transition layer gradually increases in the direction away from the work function layer; and the minimum content ratio of metal elements to non-metal elements in the second transition layer is consistent with the content ratio of metal elements to non-metal elements in the adjacent basic material layer.

[0029] In some more specific embodiments, the metal compound includes any one of TiN and TaN or a combination of two or more thereof, but is not limited thereto.

[0030] Preferably, the metal material includes Al, but is not limited thereto.

[0031] Preferably, the material of the dielectric layer includes SiO 2 、SiNx、Al 2 O 3 , HfO 2 Any one or a combination of two or more thereof, but not limited thereto.

[0032] The embodiment of the present invention further provides a method for manufacturing a GaN-based power device gate structure, which comprises:

[0033] The step of forming a dielectric layer; and the step of sequentially forming a first transition layer, one or more work function layers, a second transition layer and a stacked gate electrode layer on the dielectric layer;

[0034] The work function layer includes a basic material layer and a composite material filled in the basic material layer, wherein the composite material is at least composed of a basic material forming the basic material layer and a work function adjustment material; the first transition layer and the second transition layer are formed of the same material as the basic material layer, wherein the basic material is selected from metal compounds, and the work function adjustment material is selected from metal materials.

[0035] In some more specific embodiments, the steps of making the work function layer include: making a basic material layer, forming one or more windows on the basic material layer, and forming the composite material in the window, wherein the depth of the window is less than the thickness of the basic material layer.

[0036] In some more specific embodiments, the manufacturing method specifically includes: alternately arranging the base material and the work function adjustment material in the window in sequence, and then performing annealing treatment to form the composite material; preferably, the window has a step structure.

[0037] In some more specific embodiments, the manufacturing method includes: forming a plurality of windows on the base material layer, the plurality of windows forming a set graphic structure; arranging a work function adjustment material in the windows, and then performing annealing to form the composite material.

[0038] In some more specific embodiments, the manufacturing method includes: forming two or more work function layers on the first transition layer, and the number, shape and depth of windows on the basic material layer of two adjacent work function layers are the same or different; preferably, the number, shape and depth of windows on the basic material layer of two adjacent work function layers are different.

[0039] In some more specific embodiments, the manufacturing method specifically includes: at least using reactive sputtering to form the first transition layer and the second transition layer, and at least adjusting the content ratio of metal elements and non-metal elements in the first transition layer and the second transition layer by changing the sputtering power or changing the flow rate of the reaction gas, so that the content ratio of metal elements to non-metal elements in either the first transition layer and the second transition layer changes uniformly in a set direction.

[0040] Furthermore, the content ratio of metal elements to non-metal elements in the first transition layer increases uniformly in a direction close to the work function layer, and the content ratio of metal elements to non-metal elements in the second transition layer increases uniformly in a direction away from the work function layer.

[0041] Preferably, the maximum content ratio of the metal element to the non-metal element in any one of the first transition layer and the second transition layer is consistent with the content ratio of the metal element to the non-metal element in the adjacent base material layer.

[0042] In some more specific embodiments, the metal compound includes any one of TiN and TaN or a combination of two or more thereof, but is not limited thereto.

[0043] Preferably, the metal material includes Al, but is not limited thereto.

[0044] Preferably, the material of the dielectric layer includes SiO 2 、SiNx、Al 2 O 3 , HfO 2 Any one or a combination of two or more thereof, but not limited thereto.

[0045] An embodiment of the present invention further provides a GaN-based power device, which includes the gate structure of the GaN-based power device, and the gate structure is arranged on the substrate structure of the GaN-based power device.

[0046] The technical solution, its implementation process and principle will be further explained below in conjunction with the accompanying drawings and specific embodiments.

[0047] See also Figure 1 A GaN-based power device includes a substrate structure 100 of the device and a source S, a drain D and a gate structure arranged in cooperation with the device base structure 100, wherein the substrate structure 100 of the device includes a substrate and a heterojunction formed on the substrate, the heterojunction includes a GaN layer and an AlGaN layer arranged on the GaN layer, and a two-dimensional electron gas is formed in the heterojunction, Figure 1 The structure of the substrate structure 100 shown is only a simplified schematic diagram, and it may also include multiple layer structures such as an AlN nucleation layer, a GaN buffer layer and a cap layer, or it may be a GaN power device substrate structure such as InAlN / InGaN / (Al)GaN, etc.; the gate structure includes a dielectric layer 101, a first transition layer 102, a work function layer 103, a second transition layer 104 and a stacked gate electrode layer 105 which are sequentially arranged on the gate structure region of the substrate structure 100.

[0048] Furthermore, the material of the dielectric layer 101 can be a commonly used common dielectric material such as SiO 2 , SiN x etc., or high-K dielectric materials such as Al 2 O 3 , HfO 2etc.; the work function layer 103 includes a first work function layer and a second work function layer which are stacked, the first work function layer is arranged below the second work function layer, the first work function layer and the second work function layer both include a basic material layer, one or more windows are arranged on the basic layer material, the windows have a step structure, and the windows are filled with a composite material, the composite material is at least composed of a basic material forming the basic material layer and a work function regulating material; the material of the first transition layer and the second transition layer is the same as that of the basic material layer. The window on the base material layer of the first work function layer has a step structure composed of more than two layers of steps; a plurality of windows are arranged on the base material layer of the second work function layer, and the plurality of windows form a set graphic structure; it should be noted that the gate structure in the present invention may include only one of the first work function layer and the second work function layer or both of them. When both exist, the upper and lower positions of the first work function layer and the second work function layer are not limited, and the parameters such as the material and thickness of the base material layer of the first work function layer and the second work function layer may be the same or different; however, the content ratio of metal elements to non-metal elements in the base material layer of the first work function layer and the second work function layer is the same; preferably, the material of the base material layer (i.e., the base material) is selected from metal compounds such as TiN, TaN, CrN, NiN, etc., the work function adjustment material is selected from metal materials such as Al, and the composite material includes composite compounds such as TiAlN.

[0049] Furthermore, the material of the first transition layer 102 and the second transition layer 104 is the same as the material of the base material layer of the work function layer 103, and the content ratio of metal elements to non-metal elements in the first transition layer 102 gradually decreases in the direction away from the work function layer 103, and the maximum content ratio of metal elements to non-metal elements in the first transition layer is consistent with the content ratio of metal elements to non-metal elements in the adjacent base material layer; the content ratio of metal elements to non-metal elements in the second transition layer 104 gradually increases in the direction away from the work function layer 103; and the minimum content ratio of metal elements to non-metal elements in the second transition layer 104 is consistent with the content ratio of metal elements to non-metal elements in the adjacent base material layer.

[0050] Example 1

[0051] A method for manufacturing a gate structure of a GaN-based power device may include:

[0052] 1) forming a dielectric layer 101 on a gate region reserved on a provided GaN-based power device substrate structure 100, the formation method of which may be chemical vapor deposition or atomic layer deposition, etc., since the growth of the dielectric layer does not fall within the scope of the present invention, it will not be described in detail;

[0053] 2) A first transition layer 102 is deposited on the dielectric layer 101. The material forming the first transition layer 102 needs to be consistent with the material of the base material layer of the adjacent work function layer. For example, if the base material layer of the work function layer is TiN, then the material forming the first transition layer is also TiN. The structural cross-section of the first transition layer 102 is as follows: Figure 2 Taking TiN as an example, from the lower layer to the upper layer, the content ratio of titanium and nitrogen is less than 1, and it changes evenly from small to large. λ<1 indicates that the first transition layer is rich in nitrogen, which can prevent the metal elements of the upper work function layer from corroding downward to the dielectric layer. The value of λ depends on the demand. Figure 2 The example given is that λ is {0.25, 0.5, 0.75, 1}; the first transition layer 102 is deposited by reactive sputtering, and a smaller sputtering power is used when depositing the first transition layer, and a larger N 2 flow rate, obtain a titanium-nitrogen ratio of λ<1, and adjust the process parameters according to the change of the titanium-nitrogen ratio λ. For example, when λ is 0.25, the sputtering power used is relatively minimum, N 2 The flow rate is relatively maximum. When λ is 0.5, the sputtering power needs to be appropriately increased or N needs to be reduced. 2 The titanium-nitrogen ratio of λ = 1 is obtained by analogy;

[0054] 3) forming a work function layer 103 on the first transition layer 102, wherein the work function layer 103 is formed by doping a work function regulating material element on the base material layer 106 of the deposited work function layer 106, and controlling the distribution of the doping to modulate the distribution of the overall work function of the gate structure; Figure 3 As shown, the base material layer 106 is deposited on the first transition layer 102. The type of material is recommended to be a nitride formed by a metal with good adhesion, such as TiN, TaN, CrN or NiN. This embodiment takes TiN as an example. The work function adjustment material is generally a certain metal material. This embodiment takes aluminum as an example.

[0055] like Figure 4As shown, the layered distribution control process of the work function adjustment material element is first introduced: for example, the thickness of the base material layer 106 is 100nm, and firstly, a shallow first window 107 is etched on the base material layer 106 by using the conventional photolithography, development and etching technology. The thickness of the first window is 20nm, and a 20nm high step is formed at this time, which is called the first step; then, a larger second window 108 is formed at the same position of the first window 107 by using the ion etching technology. Since the first window 107 is located at the center of the second window 108, when etching the second window 108, the first window 107 is formed at the center of the second window 108. At the same time, the first window 107 is also etched downward, so a step is formed between the two windows, which is called the second step. For example, the etching depth of the second window 108 is 20nm, and the depth of the first window 107 is 40nm, forming a second step of 20nm height. The width of the step is determined by the difference between the size of the second window and the size of the first window. Similarly, a larger third window 109 can be etched at the position of the second window 108, so that the second window 108 is located at the center of the third window 109, and a third step is formed. For example, the etching depth of the second window 108 is also 20nm, and the depth of the third window 109 is 40nm. The depth of the first window 107 is 60nm, the depth of the second window 108 is 20nm, the depth of the first window 107 is 60nm, and the height of the third step is also 20nm; the number of steps and the width of the steps are determined according to the process requirements. Note that the depth of the first window 107 finally formed must be less than the thickness of the deposited basic material layer 106. A certain thickness of the basic material layer needs to be left for atomic diffusion in the subsequent annealing process. Next, the metal Al used to adjust the work function and the basic material layer material TiN are sequentially deposited in the first window 107 by magnetron sputtering. For example, a 10nm layer of TiN is first deposited in the window 107. Al is deposited, and then a layer of 10nm TiN is deposited, and so on, Al and TiN are deposited in the second window 108 in sequence, and then Al and TiN are alternately deposited in the third window 109 until the window is filled; finally, annealing is performed to allow the metal Al and TiN to diffuse and fuse to form TiAlN, that is, a composite material layer (the composite material layer formed by this method is a step structure with more than one step) 110; in this way, the layered distribution control of the work function adjustment material elements is formed, the desired layered distribution of the work function is obtained, the current distribution in the gate area is adjusted, and the device reaches thermal equilibrium; Figure 7 The figure shows the thermal distribution comparison of the gate channel before and after the layered distribution control process. Under the same external parameters, it can be clearly seen that the temperature distribution of the gate area is more uniform after the process, and the temperature of the gate center area is reduced.

[0056] See also Figure 5Next, the graphical distribution control process of the work function adjustment material element is introduced: first, a basic material layer 111 is deposited by magnetron sputtering. The material of the basic material layer is selected from TiN. This layer can be superimposed on the TiAlN layer after the layered distribution control process. Its thickness is determined according to the device process requirements; a mask barrier layer 112 for the stripping process is deposited on this basic material layer 111, and then the basic material layer (TiN layer) 111 is patterned and etched using a mask to form a groove pattern 113. The shape of the pattern is determined according to the electric field simulation result of the device; then Then, a work function regulating material layer 114 is deposited on the mask barrier layer 112, and the work function regulating material can be aluminum; the mask barrier layer 112 is peeled off by an etching method, leaving the work function regulating material in the groove pattern, and finally annealing is performed to form a composite material layer (i.e., a TiAlN layer, and the composite material layer formed by this method is a patterned structure composed of multiple composite material layers) 115 with a graphical distribution after annealing; in this way, the electric field distribution in the gate region can be modulated, the adverse effect of the introduction of the work function layer on the electric field density distribution can be reduced, and the breakdown voltage of the device can be improved; Figure 8 The figure shows the comparison of the electric field density distribution in the gate channel region before and after the patterned distribution control process. Through the patterned metal doping, two peak electric fields are formed, so that the maximum value of the electric field density is reduced, thereby increasing the breakdown voltage. The function layer 103 can be made according to the process requirements, and the layered distribution control process of the work function adjustment material element can be implemented only on the basic material layer or the patterned distribution control process can be implemented only.

[0057] 4) Fabrication of the second transition layer 104: A second transition layer is deposited on the work function layer. The material of the transition layer is the same as the base material layer of the adjacent work function layer, such as TiN. The content ratio λ of the titanium element and the nitrogen element in the second transition layer 104 is uniformly stepped from small to large from the lower layer to the upper layer, and λ>1, which indicates that the second transition layer is rich in titanium and can adhere well to the stacked gate electrode layer, so that the work function layer can smoothly transition to the traditional stacked gate electrode layer; the value of λ is determined according to the use requirements. Figure 6 is a cross-sectional view of the second transition layer. The example given is that λ is {1, 1.25, 1.5, 1.75, 2}. The second transition layer is also deposited by reactive sputtering. The sputtering power and the N 2 The value of λ is controlled by the flow rate.

[0058] 5) Fabrication of stacked gate electrode layer: The conventional stacked gate is composed of a metal gate electrode layer, a passivation layer, a field plate, etc. Since it is not within the scope of the present invention, the fabrication process will not be described in detail.

[0059] Therefore, the present invention introduces a work function layer and controls the distribution of work function regulating material elements, and can effectively modulate the gate region current and electric field density distribution of GaN-based power devices while adjusting the threshold voltage, so that the device reaches thermal equilibrium and improves the breakdown voltage of the device. The introduction of the first transition layer and the second transition layer located below and above the work function layer places the work function layer intact between the dielectric layer and the stacked gate electrode layer without interfering with each other, thereby increasing the reliability of the device.

[0060] The gate structure of a GaN-based power device and a manufacturing method thereof provided by an embodiment of the present invention, the layered distribution and / or graphical distribution control of the work function regulating material elements in the work function layer can effectively modulate the gate region current and electric field density distribution of the GaN-based power device, solve the adverse effects brought by the introduction of the work function layer, enable the device to reach thermal equilibrium, and improve the breakdown voltage of the device; the first transition layer and the second transition layer use a metal compound material consistent with the basic material layer of the work function layer, and by gradually changing the element ratio of the material, the first transition layer and the second transition layer play a role of blocking, protecting and adhering to the work function layer, and the work function layer is placed intact between the dielectric layer and the stacked gate electrode layer without interfering with each other, thereby increasing the reliability of the device.

[0061] The present invention has been described by the above embodiments, but it should be understood that the above embodiments are only for the purpose of example and description, and are not intended to limit the present invention to the scope of the described embodiments. In addition, it can be understood by those skilled in the art that the present invention is not limited to the above embodiments, and more variations and modifications can be made according to the teachings of the present invention, and these variations and modifications all fall within the scope of the protection claimed by the present invention. The protection scope of the present invention is defined by the attached claims and their equivalents.

Claims

1. A gate structure of a GaN-based power device, characterized in that It includes a dielectric layer, a first transition layer, a second transition layer and a stacked gate electrode layer arranged in sequence, and more than one work function layer is arranged between the first transition layer and the second transition layer, the work function layer includes a basic material layer, and more than one window is arranged on the basic material layer, and the window is filled with a composite material, and the composite material is at least formed by a composite of a basic material forming the basic material layer and a work function regulating material; the material of the first transition layer and the second transition layer is the same as that of the basic material layer, wherein the basic material is selected from one or a combination of more than two of TiN, TaN, CrN, NiN, and the work function regulating material is selected from metal Al.

2. The gate structure of a GaN-based power device according to claim 1, characterized in that: The window has a stepped structure.

3. The gate structure of the GaN-based power device according to claim 1, characterized in that: A plurality of windows are arranged on the base material layer, and the plurality of windows form a set graphic structure.

4. The gate structure of a GaN-based power device according to any one of claims 1 to 3, characterized in that: The depth of the window is less than the thickness of the base material layer.

5. The gate structure of a GaN-based power device according to any one of claims 1 to 3, characterized in that include: There are more than two work function layers, and the more than two work function layers are stacked in sequence, and the number, shape and depth of the windows on the base material layer of two adjacent work function layers are the same or different.

6. The gate structure of the GaN-based power device according to claim 5, characterized in that: The number, shape and depth of the windows on the base material layer of two adjacent work function layers are different.

7. The gate structure of a GaN-based power device according to claim 5, characterized in that: The content ratio of the metal element to the non-metal element in any one of the first transition layer and the second transition layer changes in a uniform gradient along a set direction.

8. The gate structure of a GaN-based power device according to claim 7, characterized in that: The content ratio of metal elements to non-metal elements in the first transition layer gradually decreases in the direction away from the work function layer, and the maximum content ratio of metal elements to non-metal elements in the first transition layer is consistent with the content ratio of metal elements to non-metal elements in the adjacent basic material layer; the content ratio of metal elements to non-metal elements in the second transition layer gradually increases in the direction away from the work function layer; and the minimum content ratio of metal elements to non-metal elements in the second transition layer is consistent with the content ratio of metal elements to non-metal elements in the adjacent basic material layer.

9. The gate structure of a GaN-based power device according to claim 1, characterized in that: The material of the dielectric layer includes any one of SiO2, SiNx, Al2O3, and HfO2, or a combination of two or more thereof.

10. A method for manufacturing a GaN-based power device gate structure, characterized in that include: The step of forming a dielectric layer; and the steps of sequentially forming a first transition layer, one or more work function layers, a second transition layer and a stacked gate electrode layer on the dielectric layer; The work function layer includes a basic material layer and a composite material filled in the basic material layer, wherein the composite material is at least composed of a basic material forming the basic material layer and a work function adjustment material; the first transition layer and the second transition layer are formed of the same material as the basic material layer, wherein the basic material is selected from one or a combination of two or more of TiN, TaN, CrN, and NiN, and the work function adjustment material is selected from metal Al.

11. The manufacturing method according to claim 10, characterized in that: The steps of making the work function layer include: making a basic material layer, forming more than one window on the basic material layer, and forming the composite material in the window, wherein the depth of the window is less than the thickness of the basic material layer.

12. The method according to claim 11, characterized in that Specifically include: The base material and the work function adjusting material are alternately arranged in sequence in the window, and then annealed to form the composite material.

13. The manufacturing method according to claim 12, characterized in that: The window has a stepped structure.

14. The manufacturing method according to claim 13, characterized in that: The manufacturing method comprises: forming a plurality of windows on the base material layer, the plurality of windows forming a set graphic structure; arranging a work function regulating material in the windows, and then performing an annealing treatment to form the composite material.

15. The method according to claim 11, characterized in that include: More than two work function layers are formed on the first transition layer, and the number, shape and depth of windows on the base material layer of two adjacent work function layers are the same or different.

16. The manufacturing method according to claim 15, characterized in that: The number, shape and depth of the windows on the base material layer of two adjacent work function layers are different.

17. The method according to claim 10, characterized in that Specifically include: The first transition layer and the second transition layer are formed by at least using reactive sputtering, and the content ratio of the metal element and the non-metal element in the first transition layer and the second transition layer is adjusted by at least changing the sputtering power or changing the flow rate of the reactive gas, so that the content ratio of the metal element to the non-metal element in either the first transition layer and the second transition layer changes in a uniform gradient along a set direction.

18. The manufacturing method according to claim 17, characterized in that: The content ratio of metal elements to non-metal elements in the first transition layer increases uniformly in a direction close to the work function layer, and the content ratio of metal elements to non-metal elements in the second transition layer increases uniformly in a direction away from the work function layer.

19. The method according to claim 18, characterized in that: The maximum content ratio of the metal element to the non-metal element in any one of the first transition layer and the second transition layer is consistent with the content ratio of the metal element to the non-metal element in the adjacent base material layer.

20. The manufacturing method according to claim 10, characterized in that: The material of the dielectric layer includes any one of SiO2, SiNx, Al2O3, and HfO2, or a combination of two or more thereof.

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