Semiconductor equipment

Abstract

The present invention provides a semiconductor device capable of suppressing variations in the characteristics and degradation of the breakdown voltage of MOS transistors. [Solution] The semiconductor device according to the embodiment includes a semiconductor region 10 including a drain region 12, a source region 13, and a channel region 14, an insulating layer 20 provided on the semiconductor region, a gate electrode 31, a drain contact 42, and a ring-shaped electrode 32 provided so as to surround the drain contact. The gate electrode includes a first electrode portion 31a in contact with the insulating layer and a second electrode portion 31b including a portion in contact with the insulating layer and facing the ring-shaped electrode, and the ring-shaped electrode includes a third electrode portion 32a in contact with the insulating layer and a fourth electrode portion 32b including a portion in contact with the insulating layer and facing the gate electrode, and at least one of the work function of the second electrode portion and the work function of the fourth electrode portion is different from the work function of the first electrode portion.

Description

[Technical Field]

[0001] Embodiments of the present invention relate to a semiconductor device. [Background Art]

[0002] In MOS transistors, it is desired to suppress variation in characteristics and deterioration of breakdown voltage. [Prior Art Documents] [Patent Documents]

[0003] [Patent Document 1] US Patent Application Publication No. 2017 / 0194447 Specification [Summary of the Invention] [Problem to be Solved by the Invention]

[0004] Provided is a semiconductor device capable of suppressing variation in characteristics and deterioration of breakdown voltage of a MOS transistor. [Means for Solving the Problem]

[0005] A semiconductor device according to an embodiment includes a semiconductor region including a drain region, a source region, and a channel region between the drain region and the source region; an insulating layer provided on the semiconductor region; a gate electrode provided on the insulating layer corresponding to the channel region; a drain contact connected to the drain region; and a first ring-shaped electrode provided on the insulating layer spaced apart from the gate electrode and surrounding the drain contact, wherein the gate electrode includes a first electrode portion in contact with the insulating layer and a second electrode portion adjacent to the first electrode portion, in contact with the insulating layer and facing the first ring-shaped electrode; the first ring-shaped electrode includes a third electrode portion in contact with the insulating layer and a fourth electrode portion adjacent to the third electrode portion, in contact with the insulating layer and facing the gate electrode, and at least one of the work function of the second electrode portion and the work function of the fourth electrode portion is different from the work function of the first electrode portion. [Brief explanation of the drawing]

[0006] [Figure 1] This is a schematic cross-sectional view showing the basic configuration of a semiconductor device according to an embodiment. [Figure 2] This is a schematic planar pattern diagram showing the basic configuration of the semiconductor device according to the embodiment. [Figure 3A] This figure illustrates the relationship between drain voltage and drain current in an embodiment. [Figure 3B] This figure illustrates the relationship between drain voltage and drain current in an embodiment. [Figure 3C] This figure illustrates the relationship between drain voltage and drain current in an embodiment. [Figure 4] This figure shows the electric field distribution in the region between the gate electrode and the ring-shaped electrode, relating to an embodiment. [Figure 5] This is a schematic cross-sectional view showing the configuration of a first specific example of a semiconductor device according to the embodiment. [Figure 6]This is a schematic cross-sectional view showing the configuration of a second specific example of the semiconductor device according to the embodiment. [Figure 7] This is a schematic cross-sectional view showing the configuration of a third specific example of the semiconductor device according to the embodiment. [Figure 8] This is a schematic cross-sectional view showing the configuration of a fourth specific example of the semiconductor device according to the embodiment. [Figure 9] This is a schematic cross-sectional view showing the configuration of a fifth specific example of the semiconductor device according to the embodiment. [Modes for carrying out the invention]

[0007] The embodiments will be described below with reference to the drawings.

[0008] Figure 1 is a schematic cross-sectional view showing the basic configuration of the semiconductor device according to this embodiment. Figure 2 is a schematic planar pattern diagram showing the basic configuration of the semiconductor device according to this embodiment. The semiconductor device according to this embodiment is mainly applied to high-voltage MOS transistors.

[0009] The semiconductor device according to this embodiment includes a semiconductor region 10, an insulating layer 20, a gate electrode 31, a ring-shaped electrode (first ring-shaped electrode) 32, a ring-shaped electrode (second ring-shaped electrode) 33, contacts (gate contact 41, drain contact 42, source contact 43), wiring 50, an insulating region 60, and an element isolation insulating layer 70.

[0010] The semiconductor region 10 is a region containing silicon as its main component and is provided within a semiconductor substrate such as a silicon substrate. The semiconductor region 10 includes a well region 11, a drain region 12, a source region 13, and a channel region 14.

[0011] The well region 11 includes an N-type well region 11N containing N-type impurities and a P-type well region 11P containing P-type impurities.

[0012] The drain region 12 includes a low-concentration region 12L containing a relatively low concentration of N-type impurities, and a high-concentration region 12H containing a relatively high concentration of N-type impurities. Similarly, the source region 13 includes a low-concentration region 13L containing a relatively low concentration of N-type impurities, and a high-concentration region 13H containing a relatively high concentration of N-type impurities.

[0013] The channel region 14 is a region between the drain region 12 and the source region 13, and is a region where a channel of an N-type MOS transistor is formed.

[0014] The insulating layer 20 is provided on the semiconductor region 10, formed of silicon oxide or the like, and includes a portion that functions as a gate insulating layer of the MOS transistor.

[0015] The gate electrode 31 is provided on the insulating layer 20 corresponding to the channel region 14, and functions as the gate electrode of the MOS transistor. A sidewall insulating layer 31s is provided on a sidewall of the gate electrode 31.

[0016] The ring-shaped electrode 32 is provided on the insulating layer 20 spaced apart from the gate electrode 31, and is provided so as to surround the drain contact 42. That is, when viewed from the Z direction, the pattern of the ring-shaped electrode 32 is provided so as to surround the pattern of the drain contact 42. Similarly, the ring-shaped electrode 33 is provided on the insulating layer 20 spaced apart from the gate electrode 31, and is provided so as to surround the source contact 43. That is, when viewed from the Z direction, the pattern of the ring-shaped electrode 33 is provided so as to surround the pattern of the source contact 43. Further, a sidewall insulating layer 32s is provided on a sidewall of the ring-shaped electrode 32, and a sidewall insulating layer 33s is provided on a sidewall of the ring-shaped electrode 33.

[0017] The gate contact 41 is connected to the gate electrode 31, the drain contact 42 is connected to the high-concentration region 12H of the drain region 12, and the source contact 43 is connected to the high-concentration region 13H of the source region 13. It is preferable that the drain contact 42 and the ring-shaped electrode 32 are connected in common, and the source contact 43 and the ring-shaped electrode 33 are connected in common.

[0018] The plurality of wirings 50 are provided in the insulating region 60, and include a wiring 51 connected to the gate contact 41, a wiring 52 connected to the drain contact 42, and a wiring 53 connected to the source contact 43.

[0019] The aforementioned gate electrode 31 includes an electrode portion (first electrode portion) 31a and an electrode portion (second electrode portion) 31b. Both the electrode portion 31a and the electrode portion 31b are in contact with the insulating layer 20. The electrode portion 31a functions as a main portion of the gate electrode 31. The electrode portion 31b is adjacent to the electrode portion 31a and includes a portion facing the ring-shaped electrode 32.

[0020] The aforementioned ring-shaped electrode 32 includes an electrode portion (third electrode portion) 32a and an electrode portion (fourth electrode portion) 32b. Both the electrode portion 32a and the electrode portion 32b are in contact with the insulating layer 20. The electrode portion 32b is adjacent to the electrode portion 32a and includes a portion facing the gate electrode 31.

[0021] At least one of the work function of the electrode portion 31b and the work function of the electrode portion 32b is different from the work function of the electrode portion 31a. Specifically, the following first, second and third examples can be given.

[0022] The first example is a case where the work function of the electrode portion 31b is different from the work function of the electrode portion 31a, and the work function of the electrode portion 32b is the same as the work function of the electrode portion 31a. In this case, it is preferable that the work function of the electrode portion 31b is lower than the work function of the electrode portion 31a.

[0023] A second example is when the work function of electrode portion 32b is different from that of electrode portion 31a, and the work function of electrode portion 31b is the same as that of electrode portion 31a. In this case, it is preferable that the work function of electrode portion 32b is higher than that of electrode portion 31a.

[0024] A third example is when the work function of electrode portion 31b is different from that of electrode portion 31a, and the work function of electrode portion 32b is also different from that of electrode portion 31a. In this case, it is preferable that the work function of electrode portion 31b is lower than that of electrode portion 31a, and the work function of electrode portion 32b is higher than that of electrode portion 31a.

[0025] In the first, second, and third examples, the work function of electrode portion 32a is not limited. That is, the work function of electrode portion 32a may be the same as or different from the work function of electrode portion 31a. Also, the work function of electrode portion 32a may be the same as or different from the work function of electrode portion 31b. Also, the work function of electrode portion 32a may be the same as or different from the work function of electrode portion 32b. However, usually, the work function of electrode portion 32a is the same as at least one of the work functions of electrode portion 31a and electrode portion 32b.

[0026] Furthermore, typically, among the electrode portions 31a, 31b, 32a, and 32b, those with the same work function are formed using a common process and are therefore made from the same material.

[0027] The work function of the ring-shaped electrode 33 is not particularly limited. For example, the work function of the ring-shaped electrode 33 is the same as the work function of the electrode portion 31a of the gate electrode 31.

[0028] With the above configuration, in this embodiment, it is possible to obtain a semiconductor device that can suppress variations in the characteristics and degradation of the breakdown voltage of MOS transistors, as described below.

[0029] In this embodiment, a ring-shaped electrode 32 is provided on the drain region 12 side, and a ring-shaped electrode 33 is provided on the source region 13 side. By providing the ring-shaped electrodes 32 and 33 in this way, it is possible to suppress the influence from the wiring 50. If the ring-shaped electrodes were not provided, the electric field from the wiring 50 would cause fluctuations in the potential of the drain region 12 and the source region 13, which could lead to variations in the characteristics of the MOS transistor.

[0030] In this embodiment, the ring-shaped electrodes 32 and 33 can effectively shield the electric field from the wiring 50, thereby suppressing the problems described above.

[0031] However, when a high voltage is applied to the drain region 12, the potential gradient becomes steep in the region between the gate electrode 31 and the ring-shaped electrode 32, and there is a risk that the surface breakdown voltage will deteriorate due to electric field concentration. In particular, when the potential of the drain region 12 and the potential of the ring-shaped electrode 32 are the same and an off-voltage is applied to the gate electrode 31, a large potential difference is generated between the gate electrode 31 and the ring-shaped electrode 32, and the degree of electric field concentration increases. As a result, there is a risk that the breakdown voltage of the MOS transistor will deteriorate.

[0032] In this embodiment, at least one of the work function of the electrode portion 31b of the gate electrode 31 facing the ring-shaped electrode 32 and the work function of the electrode portion 32b of the ring-shaped electrode 32 facing the gate electrode 31 is different from the work function of the electrode portion 31a of the gate electrode 31. As a result, as described below, the electric field can be weakened in the region between the gate electrode 31 and the ring-shaped electrode 32, and electric field concentration is mitigated, thereby suppressing the problems described above.

[0033] Figures 3A, 3B, and 3C show the relationship between drain voltage Vd and drain current Id.

[0034] Figure 3A shows the characteristics when the work function of the electrode portion 31b of the gate electrode 31 is changed. The work function of the electrode portion 32b of the ring-shaped electrode 32 is the same as the work function of the electrode portion 31a of the gate electrode 31. Characteristic a is the characteristic when the work function of the electrode portion 31b of the gate electrode 31 is the same as the work function of the electrode portion 31a of the gate electrode 31. Characteristic b is the characteristic when the work function of the electrode portion 31b is lower than the work function of the electrode portion 31a (work function difference of 1 eV). Characteristic c is the characteristic when the work function of the electrode portion 31b is higher than the work function of the electrode portion 31a (work function difference of 1 eV).

[0035] As shown in Figure 3A, the current decreases in characteristic b compared to characteristic a, and increases in characteristic c. In this way, when the work function of electrode portion 31b is lower than the work function of electrode portion 31a, the increase in drain current is suppressed, and the deterioration of breakdown voltage due to electric field concentration can be suppressed.

[0036] Figure 3B shows the characteristics when the work function of the electrode portion 32b of the ring-shaped electrode 32 is changed. The work function of the electrode portion 31b of the gate electrode 31 is the same as the work function of the electrode portion 31a of the gate electrode 31. Characteristic a is the characteristic when the work function of the electrode portion 32b of the ring-shaped electrode 32 is the same as the work function of the electrode portion 31a of the gate electrode 31. Characteristic b is the characteristic when the work function of the electrode portion 32b is higher than the work function of the electrode portion 31a (work function difference of 1 eV). Characteristic c is the characteristic when the work function of the electrode portion 32b is lower than the work function of the electrode portion 31a (work function difference of 1 eV).

[0037] As shown in Figure 3B, the current decreases in characteristic b compared to characteristic a, and increases in characteristic c. In this way, when the work function of electrode portion 32b is made higher than the work function of electrode portion 31a, the increase in drain current is suppressed, and it is possible to suppress the deterioration of breakdown voltage due to electric field concentration.

[0038] Figure 3C shows the characteristics when the work function of the electrode portion 31b of the gate electrode 31 and the work function of the electrode portion 32b of the ring-shaped electrode 32 are changed.

[0039] Characteristic a is the characteristic when the work function of the electrode portion 31b of the gate electrode 31 and the work function of the electrode portion 32b of the ring-shaped electrode 32 are the same as the work function of the electrode portion 31a of the gate electrode 31.

[0040] Characteristic b is the characteristic when the work function of electrode portion 31b is lower than the work function of electrode portion 31a and the work function of electrode portion 32b is higher than the work function of electrode portion 31a. Characteristic c is the characteristic when the work function of electrode portion 31b is lower than the work function of electrode portion 31a and the work function of electrode portion 32b is lower than the work function of electrode portion 31a. The work function difference is 1 eV in both cases.

[0041] Characteristic d is the characteristic when the work function of electrode portion 31b is higher than the work function of electrode portion 31a and the work function of electrode portion 32b is lower than the work function of electrode portion 31a. Characteristic e is the characteristic when the work function of electrode portion 31b is higher than the work function of electrode portion 31a and the work function of electrode portion 32b is higher than the work function of electrode portion 31a. The work function difference is 1eV in both cases.

[0042] The characteristics in Figure 3C can be said to reflect the characteristics in Figures 3A and 3B. Therefore, by appropriately setting the work function of the electrode portion 31b of the gate electrode 31 and the work function of the electrode portion 32b of the ring-shaped electrode 32, it is possible to obtain the effects described in Figures 3A and 3B more effectively.

[0043] Furthermore, comparing the characteristics of Figure 3A with those of Figure 3B, the effect of changing the work function is greater in the case of Figure 3A than in the case of Figure 3B. Therefore, for example, as shown in characteristic c of Figure 3C, if the work function of both electrode portion 31b and electrode portion 32b is made lower than the work function of electrode portion 31a, the influence of electrode portion 31b becomes dominant, and the drain current Id decreases. Thus, even in such cases, it is possible to obtain the same effect as described above.

[0044] Figure 4 shows the electric field distribution in the region between the gate electrode 31 and the ring-shaped electrode 32. The horizontal axis represents the distance x from the end of the gate electrode, and the vertical axis represents the electric field E.

[0045] Characteristic a is the case when the work function of the electrode portion 31b of the gate electrode 31 and the work function of the electrode portion 32b of the ring-shaped electrode 32 are the same as the work function of the electrode portion 31a of the gate electrode 31. Characteristic b is the case when the work function of the electrode portion 31b is lower than the work function of the electrode portion 31a (work function difference of 1 eV). Characteristic c is the case when the work function of the electrode portion 32b is higher than the work function of the electrode portion 31a (work function difference of 1 eV).

[0046] As shown in Figure 4, compared to characteristic a, the electric field in the region between the gate electrode 31 and the ring-shaped electrode 32 is relaxed in characteristics b and c. In particular, the electric field is significantly relaxed in characteristic b.

[0047] As shown in Figures 3A, 3B, 3C, and 4, by appropriately changing at least one of the work function of the electrode portion 31b of the gate electrode 31 and the work function of the electrode portion 32b of the ring-shaped electrode 32, electric field concentration can be effectively mitigated, and degradation of the breakdown voltage can be effectively suppressed.

[0048] Next, a specific example of this embodiment will be described.

[0049] Figure 5 is a schematic cross-sectional view showing the configuration of a first specific example of the semiconductor device according to this embodiment.

[0050] In this specific example, the electrode portion 31a of the gate electrode 31 and the electrode portions 32a and 32b of the ring-shaped electrode 32 are formed from the same semiconductor material (e.g., N-type polysilicon) having the same work function, while the electrode portion 31b of the gate electrode 31 is formed from a conductive material (e.g., a non-semiconductor conductive material such as a metallic material) having a lower work function than the electrode portion 31a. The sidewall insulating layer 31s includes an inner portion 31s1, and the sidewall insulating layer 32s includes an inner portion 32s1 and an outer portion 32s2.

[0051] The structure of this specific example can be formed, for example, by first forming a pattern of polysilicon layers, and then replacing a portion of the polysilicon layer with a conductive material such as a metal material.

[0052] Figure 6 is a schematic cross-sectional view showing the configuration of a second specific example of the semiconductor device according to this embodiment.

[0053] In this specific example, the electrode portion 31a of the gate electrode 31 and the electrode portions 32a and 32b of the ring-shaped electrode 32 are formed from the same semiconductor material (e.g., N-type polysilicon) having the same work function, while the electrode portion 31b of the gate electrode 31 is formed from a conductive material (e.g., a non-semiconductor conductive material such as a metallic material) having a lower work function than the electrode portion 31a. Furthermore, in this specific example, the electrode portion 31a includes a portion located on the electrode portion 31b.

[0054] The structure of this specific example can be formed, for example, by forming a first polysilicon layer, then replacing a portion of the polysilicon layer with a conductive material such as a metal, and then forming a second polysilicon layer.

[0055] Figure 7 is a schematic cross-sectional view showing the configuration of a third specific example of the semiconductor device according to this embodiment.

[0056] In this specific example, the electrode portions 31a and 31b of the gate electrode 31 and the electrode portion 32a of the ring-shaped electrode 32 are formed from the same semiconductor material having the same work function (for example, N-type polysilicon), while the electrode portion 32b of the ring-shaped electrode 32 is formed from a conductive material having a higher work function than the electrode portion 31a (for example, a conductive material other than a semiconductor, such as silicide material).

[0057] Furthermore, in this specific example, the gate electrode 31 includes an electrode portion (fifth electrode portion) 31c located on electrode portions 31a and 31b, and the ring-shaped electrode 32 includes an electrode portion (sixth electrode portion) 32c located on electrode portions 32a and 32b. Electrode portions 32b, 31c, and 32c are formed from the same silicide material.

[0058] The structure of this specific example can be formed, for example, by forming a pattern on a polysilicon layer and then silicifying the upper surface portion of the polysilicon layer, while also silicifying the side portion of the ring-shaped electrode 32 using the same process.

[0059] Figure 8 is a schematic cross-sectional view showing the configuration of a fourth specific example of the semiconductor device according to this embodiment.

[0060] In this specific example, the electrode portion 31a of the gate electrode 31 and the electrode portions 32a and 32b of the ring-shaped electrode 32 are formed from the same metallic material having the same work function, while the electrode portion 31b of the gate electrode 31 is formed from a different metallic material than the metallic materials of the electrode portions 31a, 32a, and 32b. The work function of electrode portion 31b is lower than that of electrode portions 31a, 32a, and 32b.

[0061] Figure 9 is a schematic cross-sectional view showing the configuration of a fifth specific example of the semiconductor device according to this embodiment.

[0062] In this specific example, the electrode portions 31a and 31b of the gate electrode 31 are formed from the same metallic material having the same work function, and the electrode portions 32a and 32b of the ring-shaped electrode 32 are formed from the same metallic material having the same work function. The metallic material of the electrode portions 32a and 32b is different from the metallic material of the electrode portions 31a and 31b, and the work function of the electrode portions 32a and 32b is higher than that of the electrode portions 31a and 31b.

[0063] By using structures like those shown in the first to fifth specific examples described above, it is possible to effectively obtain the effects described in the embodiments described above.

[0064] In the embodiments, the first specific example and the second specific example described above, when N-type polysilicon is used as the semiconductor material for the electrode portion 31a of the gate electrode 31, materials having a work function lower than the work function of the electrode portion 31a of the gate electrode 31 can be, for example, magnesium (Mg), indium (In), manganese (Mn), hafnium (Hf), samarium (Sm), erbium (Er), holmium (Ho), ytterbium (Yb), europium (Eu), praseodymium (Pr), erbium silicide (ErSi2), or ytterbium silicide (YbSi2).

[0065] Furthermore, in the embodiments described above and the third specific example, when N-type polysilicon is used as the semiconductor material for the electrode portion 31a of the gate electrode 31, materials having a higher work function than the work function of the electrode portion 31a of the gate electrode 31 can be, for example, molybdenum (Mo), nickel (Ni), cobalt (Co), palladium (Pd), copper (Cu), tungsten (W), gold (Au), platinum (Pt), aluminum (Al), chromium (Cr), tin (Sn), tantalum nitride (TaN), nickel silicide (NiSi2), or platinum silicide (PtSi).

[0066] Furthermore, in the embodiments described above and the fourth specific example, when tungsten (W), molybdenum (Mo), or copper (Cu) is used as the metallic material for the electrode portion 31a of the gate electrode 31, materials having a work function lower than the work function of the electrode portion 31a of the gate electrode 31 can be, for example, aluminum (Al), tin (Sn), silver (Ag), chromium (Cr), magnesium (Mg), indium (In), or manganese (Mn).

[0067] Furthermore, in the embodiments described above and the fifth specific example, when tungsten (W), molybdenum (Mo), or copper (Cu) is used as the metallic material for the electrode portion 31a of the gate electrode 31, materials having a higher work function than the work function of the electrode portion 31a of the gate electrode 31 can be, for example, cobalt (Co), nickel (Ni), platinum (Pt), gold (Au), or tantalum nitride (TaN).

[0068] While several embodiments of the present invention have been described, these embodiments are presented as examples only and are not intended to limit the scope of the invention. These novel embodiments can be carried out in a variety of other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. These embodiments and their variations are included in the scope and spirit of the invention, as well as in the claims of the invention and its equivalents. [Explanation of symbols]

[0069] 10…Semiconductor field 11...Well region 11N...N-type well region 11P...P-type well region 12...Drain region 12L...Low concentration region 12H...High concentration region 13...Source region 13L...Low concentration region 13H...High concentration region 14…Channel area 20...Insulating layer 31… gate 31a... Electrode portion (first electrode portion) 31b... Electrode portion (second electrode portion) 31c... Electrode portion (5th electrode portion) 31s... Side wall insulating layer 32... Ring-shaped electrode (first ring-shaped electrode) 32a... Electrode portion (third electrode portion) 32b... Electrode portion (fourth electrode portion) 32c... Electrode portion (sixth electrode portion) 32s... Side wall insulating layer 33... Ring-shaped electrode (second ring-shaped electrode) 33s... Side wall insulating layer 41…Gate contact 42…Drain contact 43…Source contact 50, 51, 52, 53… wiring 60...Insulating region 70...Element isolation insulating layer

Claims

1. A semiconductor region including a drain region, a source region, and a channel region between the drain region and the source region, An insulating layer provided on the semiconductor region, A gate electrode provided on the insulating layer corresponding to the channel region, A drain contact connected to the drain region, A first ring-shaped electrode is provided on the insulating layer, spaced apart from the gate electrode, and positioned to surround the drain contact, A semiconductor device equipped with, The gate electrode includes a first electrode portion in contact with the insulating layer and a second electrode portion adjacent to the first electrode portion, in contact with the insulating layer, and facing the first ring-shaped electrode. The first ring-shaped electrode includes a third electrode portion in contact with the insulating layer and a fourth electrode portion adjacent to the third electrode portion, in contact with the insulating layer, and facing the gate electrode. At least one of the work function of the second electrode portion and the work function of the fourth electrode portion is different from the work function of the first electrode portion. Semiconductor equipment.

2. The work function of the second electrode portion differs from the work function of the first electrode portion. The work function of the fourth electrode portion is the same as the work function of the first electrode portion. The semiconductor device according to claim 1.

3. The work function of the second electrode portion is lower than the work function of the first electrode portion. The semiconductor device according to claim 2.

4. The work function of the fourth electrode portion differs from the work function of the first electrode portion. The work function of the second electrode portion is the same as the work function of the first electrode portion. The semiconductor device according to claim 1.

5. The work function of the fourth electrode portion is higher than the work function of the first electrode portion. The semiconductor device according to claim 4.

6. The work function of the second electrode portion and the work function of the fourth electrode portion are different from the work function of the first electrode portion. The semiconductor device according to claim 1.

7. The work function of the second electrode portion is lower than the work function of the first electrode portion. The work function of the fourth electrode portion is higher than the work function of the first electrode portion. The semiconductor device according to claim 6.

8. The work function of the third electrode portion is the same as the work function of the first electrode portion. The semiconductor device according to claim 1.

9. The work function of the third electrode portion is the same as the work function of the fourth electrode portion. The semiconductor device according to claim 1.

10. A source contact connected to the aforementioned source region, The system further comprises a second ring-shaped electrode provided on the insulating layer, spaced apart from the gate electrode, and positioned to surround the source contact. The semiconductor device according to claim 1.

11. The material of the first electrode portion is a semiconductor material. The semiconductor device according to claim 1.

12. The material of the second electrode portion is a conductive material other than a semiconductor having a work function lower than that of the first electrode portion. The semiconductor device according to claim 11.

13. The material of the fourth electrode portion is a conductive material other than a semiconductor having a higher work function than the work function of the first electrode portion. The semiconductor device according to claim 11.

14. The first electrode portion includes a portion located on the second electrode portion. The semiconductor device according to claim 1.

15. The gate electrode further includes a fifth electrode portion located on the first electrode portion and the second electrode portion, The first ring-shaped electrode further includes a sixth electrode portion located on the third electrode portion and the fourth electrode portion, The fourth electrode portion, the fifth electrode portion, and the sixth electrode portion are formed from the same silicide material. The semiconductor device according to claim 1.

16. The material of the first electrode portion is a metallic material. The semiconductor device according to claim 1.

17. The material of the second electrode portion is a metallic material having a work function lower than that of the first electrode portion. The semiconductor device according to claim 16.

18. The material of the fourth electrode portion is a metallic material having a higher work function than the work function of the first electrode portion. The semiconductor device according to claim 16.

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