High electron mobility transistor and manufacturing method thereof

Abstract

The present invention discloses a high electron mobility transistor and a manufacturing method thereof, wherein the high electron mobility transistor comprises a first III-V compound layer, a second III-V compound layer disposed on the first III-V compound layer, the composition of the second III-V compound layer being different from that of the first III-V compound layer, and a third III-V compound layer disposed on the second III-V compound layer, wherein the first III-V compound layer and the third III-V compound layer are composed of the same Group III and Group V elements, the third III-V compound layer comprises a body and a plurality of finger-shaped portions, wherein each finger-shaped portion is connected to the body, and each finger-shaped portion is parallel to and does not contact each other, a source electrode is disposed on one side of the body and contacts the first III-V compound layer, a drain electrode is disposed on the other side of the body and contacts the first III-V compound layer, and a gate electrode is disposed directly above the body.

Description

Technical Field

[0001] The present invention relates to a structure of a high electron mobility transistor and a manufacturing method thereof, and in particular to a structure of a high electron mobility transistor with a gate extending out of a finger-shaped portion and a manufacturing method thereof. Background Art

[0002] Due to their semiconducting properties, III-V semiconductor compounds can be used to form many types of integrated circuit devices, such as high-power field-effect transistors, high-frequency transistors, and high electron mobility transistors (HEMTs). In HEMTs, two semiconductor materials with different band gaps are combined at the junction to form a heterojunction, providing a pathway for carriers. In recent years, gallium nitride (GaN) materials have become suitable for high-power and high-frequency applications due to their wide band gap and high saturation velocity. GaN-based HEMTs generate a two-dimensional electron gas (2DEG) through the piezoelectric effect of the material itself. Compared to traditional transistors, HEMTs have higher electron speed and density, thus increasing switching speed.

[0003] A great deal of research has been conducted on improving the breakdown voltage of high electron mobility transistors (HEMTs). It has been found that the breakdown of HEMTs primarily occurs below the gate sidewall near the drain. Therefore, to increase the operating performance of HEMTs, the breakdown voltage of HEMTs needs to be further improved. Summary of the Invention

[0004] In view of this, the present invention provides a high electron mobility transistor having a gate with a finger-shaped portion for improving the breakdown voltage of the high electron mobility transistor.

[0005] According to a preferred embodiment of the present invention, a high electron mobility transistor comprises:

[0006] A first III-V compound layer, a second III-V compound layer disposed on the first III-V compound layer, the composition of the second III-V compound layer being different from that of the first III-V compound layer, a third III-V compound layer disposed on the second III-V compound layer, the third III-V compound layer comprising a body and a plurality of finger-like portions, wherein each finger-like portion is connected to the body, each finger-like portion is parallel to each other and does not contact each other, a source electrode is disposed on one side of the body and contacts the first III-V compound layer, a drain electrode is disposed on the other side of the body and contacts the first III-V compound layer, and a gate electrode is disposed directly above the body.

[0007] According to another preferred embodiment of the present invention, a method for manufacturing a high electron mobility transistor includes forming a first III-V compound layer and a second III-V compound layer, the second III-V compound layer is arranged on the first III-V compound layer, and the composition of the second III-V compound layer is different from that of the first III-V compound layer, and then a third III-V compound layer is formed on the second III-V compound layer, wherein the third III-V compound layer includes a main body and multiple finger-like parts, each finger-like part is connected to the main body, and each finger-like part is parallel to each other and does not contact each other, and finally a source electrode, a drain electrode and a gate electrode are formed, wherein the source electrode is arranged on one side of the main body, the drain electrode is arranged on the other side of the main body, and the gate electrode is arranged directly above the main body.

[0008] To make the above-mentioned objectives, features, and advantages of the present invention more readily apparent, preferred embodiments are described below in detail with reference to the accompanying drawings. However, the following preferred embodiments and drawings are for reference and illustration only and are not intended to limit the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] Figure 1 A three-dimensional schematic diagram of a high electron mobility transistor according to a first preferred embodiment of the present invention;

[0010] Figure 2 is a top view of the electron mobility transistor in the first preferred embodiment of the present invention;

[0011] Figure 3 A variation of the top view of the electron mobility transistor shown in the first preferred embodiment of the present invention;

[0012] Figure 4 Another variation of the top view of the electron mobility transistor shown in the first preferred embodiment of the present invention;

[0013] Figure 5A three-dimensional schematic diagram of a high electron mobility transistor according to a second preferred embodiment of the present invention;

[0014] Figure 6 is a top view of an electron mobility transistor in a second preferred embodiment of the present invention;

[0015] Figure 7 A variation of the top view of the electron mobility transistor shown in the second preferred embodiment of the present invention;

[0016] Figure 8 Another variation of the top view of the electron mobility transistor shown in the second preferred embodiment of the present invention;

[0017] Figures 9 and 10 A schematic diagram illustrating a method for fabricating a high electron mobility transistor having a body and finger portions both having P-type dopants according to a preferred embodiment of the present invention;

[0018] Figures 11 to 12 A schematic diagram illustrating a method for fabricating a high electron mobility transistor having a body and finger portions both having P-type dopants according to another preferred embodiment of the present invention;

[0019] Figures 13 and 14 A schematic diagram illustrating a method for fabricating a high electron mobility transistor having a body and finger portions having a P-type doped compound layer and an undoped compound layer, respectively, according to a preferred embodiment of the present invention;

[0020] Figures 15 and 16 FIG1 is a schematic diagram illustrating a method for fabricating a high electron mobility transistor having a body and finger portions having a P-type doped compound layer and an undoped compound layer, respectively, according to another preferred embodiment of the present invention.

[0021] Description of main component symbols

[0022] 10: Base

[0023] 12: First III-V compound layer

[0024] 14: Second III-V compound layer

[0025] 16: Third III-V compound layer

[0026] 16a:Ontology

[0027] 16b: finger-like part

[0028] 16c: finger-like part

[0029] 18: Source electrode

[0030] 20: Drain electrode

[0031] 22: Gate electrode

[0032] 24: Two-dimensional electron gas

[0033] 26: First protective layer

[0034] 28: First Opening

[0035] 30: Second opening

[0036] 32: Second protective layer

[0037] 36: The third opening

[0038] 38: Mask layer

[0039] 40: Undoped III-V compound layer

[0040] 42: Protective layer

[0041] 44: First Opening

[0042] 46: Second opening

[0043] 100: High Electron Mobility Transistor

[0044] 200: High Electron Mobility Transistor

[0045] 300: High Electron Mobility Transistor

[0046] 400: High Electron Mobility Transistor

[0047] A: Corner DETAILED DESCRIPTION

[0048] Figure 1 FIG. 1 is a three-dimensional schematic diagram of a high electron mobility transistor according to a first preferred embodiment of the present invention. Figure 2 It is a top view of the electron mobility transistor in the first preferred embodiment of the present invention, wherein the source electrode, the drain electrode and the gate electrode are omitted in order to clearly show the structure of the third III-V compound layer.

[0049] Please also see Figure 1 and Figure 2A high electron mobility transistor 100 includes a substrate 10, a first III-V compound layer 12 covering the substrate 10, a second III-V compound layer 14 disposed on the first III-V compound layer 12, wherein the composition of the second III-V compound layer 14 is different from that of the first III-V compound layer 12, and a third III-V compound layer 16 disposed on the second III-V compound layer 14, wherein the first III-V compound layer 12 and the third III-V compound layer 16 may be composed of the same group III and group V elements or different group III and group V elements, and the third III-V compound layer 16 includes a body 16a and a plurality of finger portions 16b, wherein each finger portion 16b is connected to the body 16a, and each finger portion 16b is parallel to each other and does not contact each other. Figure 2 The body 16a and the finger portion 16b are separated by a dotted line, but these dotted lines are not present in the actual device. A source electrode 18 is disposed on one side of the body 16a and contacts the first III-V compound layer 12. A drain electrode 20 is disposed on the other side of the body 16a and contacts the first III-V compound layer 12. A gate electrode 22 is disposed directly above the body 16a. The body 16a serves as the gate of the high electron mobility transistor 100.

[0050] According to a preferred embodiment of the present invention, the first III-V compound layer 12 and the third III-V compound layer 16 may be gallium nitride or aluminum gallium nitride, but the first III-V compound layer 12 is an undoped III-V compound layer, while the third III-V compound layer 16 is a p-type III-V compound layer. For example, the first III-V compound layer 12 may be undoped gallium nitride, and the third III-V compound layer 16 may be p-type gallium nitride. Furthermore, the third III-V compound layer 16 contains no n-type dopants, i.e., no n-type dopants are present in the bulk 16a and the finger portions 16b. The second III-V compound layer 14 includes aluminum gallium nitride, aluminum indium nitride, aluminum indium gallium nitride, or aluminum nitride. In this embodiment, the second III-V compound layer 14 is undoped aluminum gallium nitride. The source electrode 18, the drain electrode 20, and the gate electrode 22 can each comprise gold, tungsten, cobalt, nickel, titanium, molybdenum, copper, aluminum, tantalum, palladium, platinum, compounds, composite layers, or alloys thereof, or copper, aluminum, or tungsten. The substrate 10 comprises a silicon substrate, a germanium substrate, a gallium arsenide substrate, a silicon germanium substrate, an indium phosphide substrate, a gallium nitride substrate, a silicon carbide substrate, or a silicon-on-insulator substrate. The high electron mobility transistor 100 is a normally-off transistor. When the high electron mobility transistor 100 is turned on, a two-dimensional electron gas 24 is formed at the interface between the first III-V compound layer 12 and the second III-V compound layer 14.

[0051] In addition, each finger-shaped portion 16b of the third III-V compound layer 16 is arranged between the main body 16a and the drain electrode 20, and the finger-shaped portion 16b extends in a direction away from the main body 16a, so that the third III-V compound layer 16 forms a comb-shaped profile. Although the number of finger-shaped portions 16b is 4 in the first preferred embodiment, the number of finger-shaped portions 16b can be adjusted according to different product requirements. It is worth noting that the electric field at the interface between the first III-V compound layer 12 and the second III-V compound layer 14 covered by the multiple finger-shaped portions 16b becomes averaged. The average electric field can improve the withstand voltage capability of the high electron mobility transistor 100, that is, the breakdown voltage of the high electron mobility transistor 100 will increase. On the other hand, if the third III-V compound layer 16 does not have the finger-shaped portion 16b and only has the main body 16a, there will be a very large electric field below the corner of the main body 16a, especially a large amount of charge will accumulate at the corner A near the drain electrode 20, which will easily generate leakage current, that is, the breakdown voltage of the electron mobility transistor 100 will be lower.

[0052] Furthermore, the present invention specifically designs the finger portions 16 b extending from the body 16 a to be disconnected from each other because, due to the gaps between the finger portions 16 b, portions of the interface between the first III-V compound layer 12 and the second III-V compound layer 14 between directly below the body 16 a and the drain electrode 20 are still uncovered by the finger portions 16 b. This allows for the generation of a two-dimensional electron gas 24. When the high electron mobility transistor 100 is turned on, the two-dimensional electron gas 24 can flow below the interface not covered by the finger portions 16 b. On the other hand, if the continuous third III-V compound layer 16 is used to completely cover the area from the body 16 a to the drain electrode 20 , no two-dimensional electron gas 24 will be generated at the interface between the first III-V compound layer 12 and the second III-V compound layer 14 between directly below the body 16 a and the drain electrode 20 . Therefore, when the high electron mobility transistor 100 is turned on, a higher voltage is required to allow electrons to pass through. In other words, the on-resistance (Ron) of the high electron mobility transistor with the continuous third III-V compound layer 16 covering the area from the body 16 a to the drain electrode 20 will be greater than the on-resistance (Ron) of the high electron mobility transistor 100 with the finger-shaped portion 16 b covering the area from the body 16 a to the drain electrode 20 .

[0053] Figure 3 FIG. 1 is a variation of the top view of the electron mobility transistor according to the first preferred embodiment of the present invention. Figure 4This is another variation of the top view of the electron mobility transistor according to the first preferred embodiment of the present invention, wherein the source electrode, the drain electrode and the gate electrode are omitted in order to clearly show the structure of the third III-V compound layer. Figure 3 and Figure 4 Elements having the same functions will be given the same reference numerals as in the first preferred embodiment.

[0054] As described above, the third III-V compound layer 16 is composed of a body 16a and a plurality of finger-shaped portions 16b. Figure 2 In the example, the finger portion 16b extends toward the drain electrode 20, that is, the finger portion 16b is only between the body 16a and the drain electrode 20, but is not limited thereto. Figure 3 As shown in FIG. 1 , the finger portion 16a extends toward the source electrode 18 and is located only between the body 16a and the source electrode 18. Figure 4 As shown, the finger portion 18 b may extend toward both the drain electrode 20 and the source electrode 18 .

[0055] Figure 5 FIG. 1 is a three-dimensional schematic diagram of a high electron mobility transistor according to a second preferred embodiment of the present invention. Figure 6 FIG2 is a top view of the electron mobility transistor in the second preferred embodiment of the present invention, wherein the source electrode, the drain electrode and the gate electrode are omitted in order to clearly show the structure of the third III-V compound layer. Figure 5 and Figure 6 Elements having the same functions will be given the same reference numerals as in the first preferred embodiment.

[0056] The difference between the first preferred embodiment and the second preferred embodiment is that the third III-V compound layer 16 in the second preferred embodiment is composed of a III-V compound layer with a p-type dopant and an undoped III-V compound layer. Specifically, the body 16a in the second preferred embodiment is composed of a III-V compound layer with a p-type dopant, while the finger portions 16c are composed of an undoped III-V compound layer. Furthermore, the III-V compound layers in the body 16a and the finger portions 16c are composed of the same Group III and Group V elements. For example, the body 16a may be p-type gallium nitride, while the finger portions 16c may be undoped gallium nitride. Furthermore, neither the body 16a nor the finger portions 16b contain n-type dopants. Other than that, the positions of other components in the second preferred embodiment are the same as those in the first preferred embodiment and are not further described here. Furthermore, regardless of whether finger portions 16b / 16c are formed from a p-type doped III-V compound layer or an undoped III-V compound layer, the only difference in high electron mobility transistor 100 / 200 is that the density of the two-dimensional electron gas 24 formed in finger portion 16b, which is a p-type doped III-V compound layer, is slightly higher than that in finger portion 16c, which is an undoped III-V compound layer. However, regardless of whether finger portions 16b / 16c are formed from a p-type doped III-V compound layer or an undoped III-V compound layer, high electron mobility transistor 100 / 200 exhibits high voltage resistance and low on-resistance.

[0057] Figure 7 FIG. 1 is a variation of the top view of the electron mobility transistor according to the second preferred embodiment of the present invention. Figure 8 This is another variation of the top view of the electron mobility transistor according to the second preferred embodiment of the present invention, wherein in order to clearly show the structure of the third III-V compound layer, Figure 7 and Figure 8 The source electrode, drain electrode and gate electrode are omitted in Figure 7 and Figure 8 Elements having the same functions will be given the same reference numerals as in the first preferred embodiment.

[0058] exist Figure 6 In the example, the finger portion 16c extends toward the drain electrode 20, that is, the finger portion 16c is only between the body 16a and the drain electrode 20, but is not limited thereto. Figure 7 As shown, the finger portion 16c extends toward the source electrode 18 and is only between the body 16a and the source electrode 18. Figure 8 The finger portion 16 c shown may extend toward both the drain electrode 20 and the source electrode 18 .

[0059] Several methods of fabricating the high electron mobility transistor of the present invention are described below as examples, but the high electron mobility transistor of the present invention is not limited to these fabrication methods. Figures 9 and 10 A method for manufacturing a high electron mobility transistor in which both the body and the finger portions have P-type dopants according to a preferred embodiment of the present invention is shown. Figures 11 to 12 A method for fabricating a high electron mobility transistor with both the body and the finger portions having P-type dopants according to another preferred embodiment of the present invention is shown, wherein elements having the same functions are labeled the same as those in the first preferred embodiment.

[0060] like Figure 9 As shown, a substrate 10 is first provided, and then a first III-V compound layer 12 and a second III-V compound layer 14 are sequentially formed to cover the substrate 10, and a third III-V compound layer 16 is formed and disposed on the second III-V compound layer 14. According to a preferred embodiment of the present invention, the first III-V compound layer 12 and the third III-V compound layer 16 are both gallium nitride, but the first III-V compound layer 12 is undoped gallium nitride, the third III-V compound layer 16 is p-type gallium nitride, and the second III-V compound layer 14 is undoped aluminum gallium nitride.

[0061] like Figure 10 As shown, a photolithography process is performed to pattern the third III-V compound layer 16 so that the third III-V compound layer 16 forms a body 16a and a plurality of finger-shaped portions 16b, wherein the finger-shaped portions 16b extend from the body 16a. Figure 1 As shown, a source electrode 18 and a drain electrode 20 are formed simultaneously on both sides of the third III-V compound layer 16. The source electrode 18 and the drain electrode 20 contact the first III-V compound layer 12 and the second III-V compound layer 14. Then, a gate electrode 22 is formed to contact the body 16a. At this point, the high electron mobility transistor 100 of the present invention is completed.

[0062] According to another production method of the present invention, Figure 11 As shown, a substrate 10 is first provided, and then a first III-V compound layer 12 and a second III-V compound layer 14 are sequentially formed to cover the substrate 10. A first protective layer 26 is then formed to cover the second III-V compound layer. The first protective layer 26 is then patterned, and a first opening 28 is etched in the first protective layer 26 as the predetermined location for the subsequent third III-V compound layer 16. A third III-V compound layer 16 is then formed to fill the first opening 28. At this point, the third III-V compound layer 16 conforms to the shape of the first opening 28 to form a body 16a and finger-shaped portions 16b.

[0063] like Figure 12 As shown, the first protective layer 26 is etched again, forming two second openings 30 in the first protective layer to expose the first III-V compound layer 12. The two second openings 30 serve as predetermined locations for the subsequent formation of the source electrode 18 and the drain electrode 20. The source electrode 18 and the drain electrode 20 are then formed to fill the second openings 30. A second protective layer 32 is then formed to cover the first protective layer 26, the third III-V compound layer 16, the source electrode 18, and the drain electrode 20. The second protective layer 32 is then etched to form a plurality of third openings 36 in the second protective layer. The third openings 36 expose the body 16a, the source electrode 18, and the drain electrode 20. The gate electrode 22 is then formed to fill the third openings 36, such that the gate electrode 22 contacts the body 16a. At this point, the high electron mobility transistor 300 of the present invention is completed. The first protective layer 26 and the second protective layer 32 can be made of silicon nitride or aluminum nitride.

[0064] Figures 13 and 14 A method for fabricating a high electron mobility transistor having a body and finger portions with a P-type doped compound layer and an undoped compound layer, respectively, according to a preferred embodiment of the present invention is shown. Figures 15 and 16 According to another preferred embodiment of the present invention, a method for manufacturing a high electron mobility transistor having a body and finger-shaped portions with a P-type doped compound layer and an undoped compound layer, respectively, is illustrated, wherein elements having the same functions will use the same reference numerals as in the first preferred embodiment.

[0065] like Figure 13 As shown, a substrate 10 is first provided, and then a first III-V compound layer 12, a second III-V compound layer 14, and a III-V compound layer with P-type doping are sequentially formed to cover the substrate 10. According to a preferred embodiment of the present invention, the first III-V compound layer 12 is undoped gallium nitride, the III-V compound layer with P-type doping is P-type gallium nitride, and the second III-V compound layer 14 is undoped aluminum gallium nitride. Then, a mask layer 38 is formed to cover the III-V compound layer with P-type doping, and then the mask layer 38 is patterned. Thereafter, the III-V compound layer with P-type doping is patterned using the mask layer 38 as a mask to form a body 16a. Figure 14 As shown, an undoped III-V compound layer 40 is formed to cover the second III-V compound layer. Figure 5As shown, after removing the mask layer 38, the undoped III-V compound layer 40 is patterned to form a plurality of finger-shaped portions 16c. At this time, the undoped III-V compound layer 40 and the III-V compound layer with P-type dopants constitute the third III-V compound layer 16. Then, a source electrode 18, a drain electrode 20, and a gate electrode 22 are formed, wherein the source electrode 18 and the drain electrode 20 contact the first III-V compound layer 12, and the gate electrode 22 contacts the body 16a.

[0066] According to another manufacturing method of the present invention, Figure 13 After the body 16a has been formed, Figure 15 As shown, the mask layer 38 is removed, and then a protective layer 42 is formed to cover the body 16a and the second III-V compound layer 14. The protective layer 42 is patterned to form a first opening 44 on the protective layer 42 to define the predetermined position of the finger portion 16c, and the second III-V compound layer 14 is exposed through the first opening 44. Then, an undoped III-V compound layer is formed to fill the first opening 44 to form the finger portion 16c. Figure 16 As shown, the protective layer 42 is patterned to form a plurality of second openings 46 on the protective layer 42 to define the predetermined positions of the source electrode 18, the drain electrode 20, and the gate electrode 22. Then, the source electrode 18, the drain electrode 20, and the gate electrode 22 are formed to fill the second openings 46, respectively. The source electrode 18 and the drain electrode 20 contact the first III-V compound layer 12, and the gate electrode 22 contacts the body 16a. At this point, the high electron mobility transistor 400 of the present invention is completed.

[0067] The present invention specifically extends the body of the normally-off high electron mobility transistor into several finger-shaped portions, so that the electric field at the interface between the first III-V compound layer and the second III-V compound layer covered by the finger-shaped portions can be averaged, thereby increasing the withstand voltage capability of the high electron mobility transistor.

[0068] The above descriptions are merely preferred embodiments of the present invention. All equivalent changes and modifications made according to the claims of the present invention should fall within the scope of the present invention.

Claims

1. A high electron mobility transistor, characterized in that Include: a first III-V compound layer; a second III-V compound layer disposed on the first III-V compound layer, wherein the composition of the second III-V compound layer is different from that of the first III-V compound layer; a third III-V compound layer disposed on the second III-V compound layer, the third III-V compound layer comprising a body and a plurality of finger-shaped portions, wherein the plurality of finger-shaped portions are connected to the body, and the finger-shaped portions are parallel to each other and do not contact each other; a source electrode disposed on one side of the body and contacting the first III-V compound layer, wherein the body is a III-V compound layer having a P-type dopant, and the plurality of finger-shaped portions are undoped III-V compound layers; a drain electrode disposed on the other side of the body and contacting the first III-V compound layer; as well as A gate electrode is disposed directly above the body, wherein the gate electrode does not contact the second III-V compound layer.

2. The high electron mobility transistor of claim 1 , wherein the first III-V compound layer comprises gallium nitride or aluminum gallium nitride, the third III-V compound layer comprises gallium nitride or aluminum gallium nitride, and the second III-V compound layer comprises aluminum gallium nitride, aluminum indium nitride, aluminum indium gallium nitride, or aluminum nitride. 3 . The high electron mobility transistor as claimed in claim 1 , wherein the plurality of finger-shaped portions are disposed only between the body and the drain electrode. 4 . The high electron mobility transistor as claimed in claim 1 , wherein the plurality of finger-shaped portions are disposed only between the body and the source electrode. 5 . The high electron mobility transistor of claim 1 , wherein the plurality of finger-shaped portions are disposed between the body and the drain electrode and between the body and the source electrode. The high electron mobility transistor of claim 1 , wherein the plurality of finger portions are free of N-type dopants. 7 . The high electron mobility transistor as claimed in claim 1 , wherein each of the finger-shaped portions extends in a direction away from the body.

8. A method for manufacturing a high electron mobility transistor, comprising: forming a first III-V compound layer and a second III-V compound layer, wherein the second III-V compound layer is disposed on the first III-V compound layer, and the composition of the second III-V compound layer is different from that of the first III-V compound layer; forming a third III-V compound layer disposed on the second III-V compound layer, wherein the third III-V compound layer comprises a body and a plurality of finger-shaped portions, the plurality of finger-shaped portions being connected to the body, and the finger-shaped portions being parallel to and not in contact with each other, wherein the body is a III-V compound layer having a P-type dopant, and the plurality of finger-shaped portions are undoped III-V compound layers; and A source electrode, a drain electrode and a gate electrode are formed, wherein the source electrode is arranged on one side of the body, the drain electrode is arranged on the other side of the body and the gate electrode is arranged directly above the body, wherein the gate electrode does not contact the second III-V compound layer.

9. The method for fabricating a high electron mobility transistor according to claim 8, wherein the third III-V compound layer is formed by: forming a III-V compound layer having a P-type dopant; patterning the III-V compound layer having P-type dopants to form the body; After forming the body, forming an undoped III-V compound layer to cover the second III-V compound layer; patterning the undoped III-V compound layer to form the plurality of finger-shaped portions; After forming the body and the plurality of finger-shaped portions, the source electrode, the drain electrode, and the gate electrode are formed, wherein the source electrode and the drain electrode contact the first III-V compound layer, and the gate electrode contacts the body.

10. The method for fabricating a high electron mobility transistor according to claim 8, wherein the third III-V compound layer is formed by: forming a III-V compound layer having a P-type dopant; patterning the III-V compound layer having P-type dopants to form the body; forming a protective layer covering the body and the second III-V compound layer; Patterning the protective layer to form a first opening on the protective layer to define predetermined positions of the plurality of finger-shaped portions, and the second III-V compound layer is exposed through the first opening; forming an undoped III-V compound layer to fill the first opening to form the plurality of finger-shaped portions; After forming the plurality of finger-shaped portions, patterning the protective layer to form a plurality of second openings on the protective layer to respectively define predetermined positions of the source electrode, the drain electrode, and the gate electrode; as well as The source electrode, the drain electrode, and the gate electrode are formed to fill the second openings, wherein the source electrode and the drain electrode contact the first III-V compound layer, and the gate electrode contacts the body. 11 . The method for fabricating a high electron mobility transistor according to claim 8 , wherein the first III-V compound layer and the third III-V compound layer are gallium nitride, and the second III-V compound layer comprises aluminum gallium nitride, aluminum indium nitride, aluminum indium gallium nitride, or aluminum nitride. 12 . The method for fabricating a high electron mobility transistor as claimed in claim 8 , wherein the plurality of finger-shaped portions are only disposed between the body and the drain electrode. 13 . The method for fabricating a high electron mobility transistor as claimed in claim 8 , wherein the plurality of finger-shaped portions are only disposed between the body and the source electrode. 14 . The method for fabricating a high electron mobility transistor according to claim 8 , wherein the plurality of finger-shaped portions are disposed between the body and the source electrode and between the body and the drain electrode. 15 . The method for fabricating a high electron mobility transistor as claimed in claim 8 , wherein the plurality of finger-shaped portions do not contain N-type dopants. 16 . The method for fabricating a high electron mobility transistor as claimed in claim 8 , wherein each of the finger-shaped portions extends in a direction away from the body.

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