Semiconductor Devices

Abstract

To sufficiently reduce the on-resistance of a semiconductor device.SOLUTION: A semiconductor device of the present invention comprises a plurality of columnar parts formed of a semiconductor. Each of the plurality of columnar parts has a source region, a drain region, and a channel forming region that includes a channel formed between the source region and the drain region. The semiconductor device of the present invention further comprises: a gate electrode that is provided on a side wall of the channel forming region with an insulating layer therebetween; and a first semiconductor layer that is provided on side walls of the drain regions. The conductivity type of the first semiconductor layer is different from the conductivity type of the semiconductor that forms the drain region.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a semiconductor device. [Background technology]

[0002] Semiconductor nanowires are thin semiconductor wires with nanometer (nm)-order thicknesses, and are attracting attention as next-generation nanodevices for use in various semiconductor devices, such as transistors and light sources. Furthermore, by adopting a gate-all-around (GAA) structure in which a semiconductor nanowire is completely surrounded by a gate electrode, the channel formation region of the semiconductor nanowire is completely surrounded by the gate electrode, resulting in complete depletion and improved current controllability. The GAA structure allows for both rapid on / off switching over time and high density per unit area.

[0003] For example, Non-Patent Document 1 discloses a semiconductor device including multiple semiconductor nanowires formed of gallium nitride (GaN). In the semiconductor device disclosed in Patent Document 1, multiple semiconductor nanowires are arranged at intervals in one direction on the surface of a substrate, and each semiconductor nanowire extends in a direction perpendicular to the one direction. In other words, the multiple semiconductor nanowires are formed in a stripe pattern when viewed in a direction perpendicular to the surface of the substrate. In addition, the channel of the vertical transistor is formed by the a-plane of GaN. Chromium (Cr) is used for the gate electrode. [Prior art documents] [Non-patent literature]

[0004] [Non-Patent Document 1] F. Yu et al., “Vertical architecture for enhancement mode power transistors based on GaN nanowires,” Appl. Phys. Lett. Vol. 108, 213503 (2016). Summary of the Invention [Problem to be solved by the invention]

[0005] In the semiconductor device disclosed in Patent Document 1, multiple semiconductor nanowires are formed top-down using a dry etching process. After the dry etching process, a wet process using an alkaline agent or the like is used to restore the GaN crystallinity of the multiple semiconductor nanowires. This results in a large pitch between the semiconductor nanowires, making it difficult to achieve a high density of semiconductor nanowires per area on the array surface. Furthermore, the process using the alkaline agent or the like tends to result in the GaN a-plane forming the channel surface, making it difficult to achieve a high surface density. Furthermore, in the semiconductor device disclosed in Patent Document 1, after the semiconductor nanowires are formed, a gate electrode is formed by obliquely evaporating Cr onto the sidewalls of the semiconductor nanowires, making it difficult to control the gate length. Due to these factors, it is difficult to sufficiently reduce the on-resistance of the semiconductor device disclosed in Patent Document 1 to the level required for power devices. [Means for solving the problem]

[0006] To solve the above problems, one aspect of the present invention provides a semiconductor device comprising a plurality of pillar-shaped portions made of a semiconductor. Each of the plurality of pillar-shaped portions has a source region, a drain region, and a channel formation region including a channel formed between the source region and the drain region. The semiconductor device of one aspect of the present invention further comprises a gate electrode provided on a sidewall of the channel formation region via an insulating layer, and a first semiconductor layer provided on a sidewall of the drain region. The conductivity type of the first semiconductor layer is different from the conductivity type of the semiconductor forming the drain region. [Brief explanation of the drawings]

[0007] [Figure 1] 1 is a perspective view of a semiconductor device according to an embodiment of the present invention; [Figure 2]2 is a cross-sectional view of the semiconductor device shown in FIG. 1 taken along the line C1-C1 shown in FIG. [Figure 3] 3 is a cross-sectional view for explaining a method of manufacturing the semiconductor device shown in FIG. 1 and FIG. 2. [Figure 4] 3 is a cross-sectional view for explaining a method of manufacturing the semiconductor device shown in FIG. 1 and FIG. 2. [Figure 5] 3 is a cross-sectional view for explaining a method of manufacturing the semiconductor device shown in FIG. 1 and FIG. 2. [Figure 6] 3 is a cross-sectional view for explaining a method of manufacturing the semiconductor device shown in FIG. 1 and FIG. 2. [Figure 7] 3 is a cross-sectional view for explaining a method of manufacturing the semiconductor device shown in FIG. 1 and FIG. 2. [Figure 8] 3 is a cross-sectional view for explaining a method of manufacturing the semiconductor device shown in FIG. 1 and FIG. 2. [Figure 9] 3 is a cross-sectional view for explaining a method of manufacturing the semiconductor device shown in FIG. 1 and FIG. 2. [Figure 10] 3 is a cross-sectional view for explaining a method of manufacturing the semiconductor device shown in FIG. 1 and FIG. 2. [Figure 11] 3 is a cross-sectional view for explaining a method of manufacturing the semiconductor device shown in FIG. 1 and FIG. 2. [Figure 12] 3 is a cross-sectional view for explaining a method of manufacturing the semiconductor device shown in FIG. 1 and FIG. 2. [Figure 13] 3 is a cross-sectional view for explaining a method of manufacturing the semiconductor device shown in FIG. 1 and FIG. 2. [Figure 14] 3 is a cross-sectional view for explaining a method of manufacturing the semiconductor device shown in FIG. 1 and FIG. 2. [Figure 15] 3 is a cross-sectional view for explaining a method of manufacturing the semiconductor device shown in FIG. 1 and FIG. 2. [Figure 16] 3 is a cross-sectional view for explaining a method of manufacturing the semiconductor device shown in FIG. 1 and FIG. 2. [Figure 17] 3 is a cross-sectional view for explaining a method of manufacturing the semiconductor device shown in FIG. 1 and FIG. 2. [Figure 18] 3 is a cross-sectional view for explaining a method of manufacturing the semiconductor device shown in FIG. 1 and FIG. 2. [Figure 19] 3 is a cross-sectional view for explaining a method of manufacturing the semiconductor device shown in FIG. 1 and FIG. 2. [Figure 20] 3 is a cross-sectional view for explaining a method of manufacturing the semiconductor device shown in FIG. 1 and FIG. 2. DETAILED DESCRIPTION OF THE INVENTION

[0008] Hereinafter, one embodiment of the present invention will be described with reference to FIGS. In the drawings below, the dimensions of some components may be scaled differently to make them easier to see.

[0009] (Basic structure of semiconductor device) FIG. 1 is a perspective view of a semiconductor device 11 according to one embodiment of the present invention. FIG. 2 is a cross-sectional view of the semiconductor device 11 taken along the C1-C1 line in FIG. 1 . As shown in FIGS. 1 and 2 , the semiconductor device 11 includes multiple vertical field-effect transistors (FETs) and is used as a power device such as an inverter. The semiconductor device 11 mainly includes a metal layer 12 constituting a source-side contact region, a semiconductor layer (second semiconductor layer) 20 and a semiconductor layer (semiconductor) 21C constituting a source region S of the FET, a semiconductor layer (semiconductor) 21A and a semiconductor layer 30 constituting a drain region D of the FET, a semiconductor layer (semiconductor) 21B constituting a channel formation region R of the FET, a gate insulating film (insulating layer) 40, a gate electrode 50, a metal layer (first metal layer) 60 constituting a drain-side contact region of the FET, and a semiconductor layer (first semiconductor layer) 70. Note that although the gate insulating film 40 is omitted in FIG. 1 , it is interposed between the semiconductor layer 21B and the gate electrode 50, as described below.

[0010] In the following description, the Z direction is a direction parallel to the thickness direction of, for example, the metal layer 12 of the semiconductor device 11, and a direction from the front surface 12a to the back surface 12b of the metal layer 12. Two directions parallel to the front surface 12a of the metal layer 12 and perpendicular to each other are defined as the X direction and the Y direction. The Z direction is perpendicular to the X direction and the Y direction.

[0011] In addition to the above-described components, the semiconductor device 11 may further include, for example, a gate conductive layer directly connected to the gate electrode 50 in the Z direction and a gate metal layer provided on the opposite side of the gate conductive layer from the gate electrode 50, although these are not shown. The semiconductor device 11 may also include, for example, a source conductive layer directly connected to the semiconductor layer 20 of the source region S in the Z direction and a source metal layer provided on the opposite side of the source conductive layer from the semiconductor layer 20. Alternatively, wire bonding may be provided on the gate electrode 50 and wire bonding may be provided on the metal layer 12. The gate conductive layer and the source conductive layer function as contact plugs. The gate metal layer functions as a contact terminal to the gate electrode 50, and the source metal layer functions as a contact terminal to the source region S of the FET. The gate conductive layer and the source conductive layer are each formed of, for example, tungsten (W). The gate metal layer and the source metal layer are each formed of, for example, copper (Cu) or aluminum (Al). When the gate electrode 50 is provided with a wire bond and the metal layer 12 is provided with a wire bond, each of the wire bonds may be made of a metal such as copper (Cu) or aluminum (Al).

[0012] 1 and 2, the metal layer 60 serves as a substrate supporting the main components of the semiconductor device 11, extends along the XY plane, and has a predetermined thickness. Because a metal layer has a higher strength than a semiconductor layer at a given thickness, the predetermined thickness may be thinner than that of a semiconductor substrate used in a conventional semiconductor device. The front surface 60a and back surface 60b of the metal layer 60 are flat surfaces approximately parallel to the XY plane. The metal layer 60 is formed of a metal such as Cu.

[0013] Semiconductor layer (Third semiconductor layer)The semiconductor layer 30 is stacked behind the surface 60a of the metal layer 60 in the Z direction, extends along the XY plane, and has a predetermined thickness. The surface 30a and bottom surface 30b of the semiconductor layer 30 are flat surfaces approximately parallel to the XY plane. The semiconductor layer 30 is formed of, for example, an n-type semiconductor. The n-type semiconductor is, for example, gallium nitride (GaN) doped with n-type impurities. Examples of n-type impurities include silicon (Si).

[0014] The semiconductor layer 30 has a two-layer structure including a first layer 31 and a second layer 32. The first layer 31 extends along the XY plane and is disposed on the rear side of the semiconductor layer 30 in the Z direction, i.e., at the bottom of the semiconductor layer 30. A bottom surface 31b of the first layer 31 abuts on a surface 60a of the metal layer 60. The second layer 32 is provided between the first layer 31 and each of the multiple columnar sections 22 in the Z direction, extends along the XY plane, and is disposed on the front side of the semiconductor layer 30 in the Z direction, i.e., at the top of the semiconductor layer 30. A surface 32a of the second layer 32 abuts on the bottom surfaces 22b of the multiple columnar sections 22. A bottom surface 32b of the second layer 32 abuts on a surface 31a of the first layer.

[0015] The first layer 31 is formed of an n-type semiconductor, for example, n-type GaN. Hereinafter, GaN doped with n-type impurities may be referred to as n-GaN. The second layer 32 is formed of an n-type semiconductor with a lower impurity concentration than the n-type semiconductor that forms the first layer 31. Hereinafter, n-GaN with a relatively higher impurity concentration will be referred to as n-GaN. + -GaN is written as n-GaN, and those with relatively low impurity concentrations are written as n - In other words, the first layer 31 is n + -GaN, and the second layer 32 is n - -It is made of GaN.

[0016] The semiconductor layer 21A, the semiconductor layer 21B, and the semiconductor layer 21C are sequentially stacked in the Z direction, have the same shape and size in the XY plane, and form a single columnar portion (columnar portion) 22. The columnar portion 22 is a so-called semiconductor nanowire. In other words, the semiconductor device 11 includes a plurality of columnar portions 22. The plurality of columnar portions 22 are arranged at predetermined intervals from each other along both the X and Y directions. Each of the plurality of columnar portions 22 protrudes parallel to and in the opposite direction to the Z direction from a predetermined region of the surface 20a of the semiconductor layer 20 that forms the source region S. The cross section of each of the plurality of columnar portions 22 intersecting the XY plane is, for example, circular, but may also be rectangular or a polygon other than a rectangle.

[0017] The maximum size in the XY plane of each of the plurality of columnar portions 22 is, for example, about 0.3 μm, and is at least 0.5 μm or less. Because the plurality of columnar portions 22 have a small diameter as described above, the region Ch where the channel is formed can easily reach approximately the center of the semiconductor layer 21C in the XY plane, enabling complete depletion.

[0018] In the claims, "semiconductor" collectively refers to the semiconductor 21 that constitutes the columnar portion 22, and does not mean that the semiconductor layers 21A, 21B, and 21C are made of the same type of semiconductor, but includes the same or different types of semiconductors that have different impurity concentrations while satisfying the conditions described below.

[0019] The semiconductor layer 21A is disposed at the front end in the Z direction of the columnar section 22, i.e., at the bottom layer, and constitutes the drain region D together with the semiconductor layer 30. The bottom surface 22b of each of the plurality of columnar sections 22 abuts against the surface 30a of the semiconductor layer 30. By being disposed in this manner, the semiconductor layer 30 is connected to each of the semiconductor layers 21A of the plurality of columnar sections 22. The semiconductor layer 21A is formed of an n-type semiconductor, and may have the same n-type conductivity as the second layer 32 of the semiconductor layer 30, for example. --GaN. Although not shown, the semiconductor layer 21A constituting the drain region D may include a first region and a second region having a lower impurity concentration than the first region, and the second region may be located between the first region and the semiconductor layer 21B. In this case, the impurity concentration of the second region is lower than that of the first region and higher than that of the semiconductor layer 21B. The second region is a drift region.

[0020] The semiconductor layer 21B is disposed as an intermediate layer between the semiconductor layers 21A and 21C of the columnar portion 22 in the Z direction, and constitutes a channel formation region R. The channel formation region R includes a region Ch where a channel is formed between the source region S and the drain region D, and is a region where a gradient occurs due to the difference in impurity concentration between the semiconductor 21 that forms each of the semiconductor layers 21A and 21C, and where the drift velocity of charges increases when a gate voltage is applied. The size of the semiconductor layer 21B in the Z direction is smaller than the size of each of the semiconductor layers 21A and 21C in the Z direction.

[0021] The semiconductor layer 21B is formed of, for example, a semiconductor that is not doped with impurities. An example of a semiconductor that is not doped with impurities is GaN. Hereinafter, GaN that is barely doped with impurities may be referred to as i-GaN. The semiconductor layer 21B may be formed of any semiconductor with a lower impurity concentration than the n-type semiconductor that forms the semiconductor layers 21A and 21C, and is not necessarily limited to a semiconductor that is not doped with impurities. However, as the impurity concentration of the semiconductor layer 21B approaches that of the semiconductor layer 21A, the on-resistance of the FET decreases, but the breakdown voltage also decreases. The on-resistance and the breakdown voltage are in a trade-off relationship. The impurity concentration of the semiconductor layer 21B is appropriately set taking into consideration the impurity concentration and size in the Z direction of the semiconductor layer 21A and the aforementioned trade-off relationship. In the semiconductor device 11 of this embodiment, a super junction (SJ) structure is formed by the semiconductor layer 21B and the semiconductor layer 70, as described below. The SJ structure reduces the on-resistance. Therefore, the impurity concentration of the semiconductor layer 21B is preferably low, giving priority to ensuring the breakdown voltage of the FET, and is preferably close to zero, i.e., no impurities are doped.

[0022] The semiconductor layers 21A, 21B, and 21C are preferably made of the same type of semiconductor, such as GaN in this embodiment. By forming the semiconductor layers 21A, 21B, and 21C from the same type of semiconductor 21, the process of forming the multiple columnar portions 22 can be performed continuously and easily during the manufacture of the semiconductor device 11.

[0023] Furthermore, GaN can convert power more efficiently than other semiconductors, so the electrical power that can be output per volume of GaN is relatively high. The band gap of GaN is approximately three times larger than that of Si, which is widely used in conventional power devices. Furthermore, the breakdown field of GaN is one order of magnitude larger than that of Si, so the on-resistance can be reduced by approximately three orders of magnitude compared to the performance limit caused by Si. Furthermore, the saturated electron velocity of GaN is higher than that of Si, etc., so the operation speed of the semiconductor device 11 can be increased.

[0024] The semiconductor layer 21C is disposed at the rear end, i.e., the uppermost layer, of the columnar section 22 in the Z direction, and constitutes the source region S. The size of the semiconductor layer 21C in the Z direction is at least larger than the size of the semiconductor layer 21B in the Z direction, and slightly smaller than the size of the semiconductor layer 21A in the Z direction. The semiconductor layer 21C is formed of, for example, an n-type semiconductor. The n-type semiconductor is, for example, n-GaN doped with n-type impurities such as Si, as described above.

[0025] The impurity concentration of the n-type semiconductor forming the semiconductor layer 21C is higher than at least the impurity concentration of the semiconductor forming the semiconductor layer 21B, and is also higher than the impurity concentration of the semiconductor forming the semiconductor layer 21A. - The semiconductor layer 21B is made of i-GaN, and the semiconductor layer 21C is made of n-GaN. + That is, the impurity concentration of the first region and the impurity concentration of the second region of the semiconductor layer 21A are both lower than the impurity concentration of the semiconductor layer 21C.

[0026] Because the size of semiconductor layer 21A in the Z direction is larger than that of semiconductor layer 21C and the impurity concentration of the semiconductor forming semiconductor layer 21A is lower than that of semiconductor layer 21C, a wide depletion layer of the FET is ensured, thereby ensuring the breakdown voltage of semiconductor device 11. Furthermore, a vertical FET is configured by multiple columnar portions 22, the size of semiconductor layer 21B in the Z direction is kept smaller than that of semiconductor layers 21A and 21C, and GaN is used as semiconductor 21, so that the on-resistance per area at surface 30a of semiconductor layer 30 of semiconductor device 11 is reduced to some extent.

[0027] The semiconductor layer 20, together with the semiconductor layer 21C, constitutes a source region S. The semiconductor layer 20 extends along the XY plane, and connects the semiconductor layers 21C of the multiple columnar sections 22 together along the XY plane. The bottom surface 20b of the semiconductor layer 20 abuts on the surfaces 22a of the multiple columnar sections 22. By being arranged in this manner, the semiconductor layer 30 is connected to the semiconductor layers 21C of the multiple columnar sections 22. The semiconductor layer 20 is made of the same type of semiconductor as the semiconductor layers 30, 21A, 21B, and 21C, and is made of GaN. The semiconductor layer 20 is made of, for example, an n-type semiconductor, and in this embodiment, is an n-type semiconductor, like the semiconductor layer 21C. + That is, in the semiconductor device 11, the semiconductor layers 20 and 21C and the first layer 31 of the semiconductor layer 30 are made of n-GaN. + -GaN, and the semiconductor layer 21A and the second layer 32 of the semiconductor layer 30 are n-GaN. - The semiconductor layer 21B is made of i-GaN, and the semiconductor layer 21B is made of i-GaN.

[0028] The metal layer 12 is stacked on the front surface 20a of the semiconductor layer 20 to form a contact region and is connected to the semiconductor layer 20. The metal layer 12 faces the metal layer 60 in the Z direction, plays the role of an opposing base material that supports the main components of the semiconductor device 11, and has a predetermined thickness. The front surface 12a and back surface 12b of the metal layer 12 are flat surfaces approximately parallel to the XY plane. The metal layer 12 is formed of a metal such as aluminum (Al) or Cu.

[0029] The gate electrode 50 is provided on at least the sidewall 21r of the semiconductor layer 21B in the channel formation region R via the gate insulating film 40. The size of the gate electrode 50 in the Z direction is larger than that of the semiconductor layer 21B. When viewed in the Z direction, the gate electrode 50 overlaps the end of the semiconductor layer 21A on the channel formation region R side and the end of the semiconductor layer 21C on the channel formation region R side. That is, the size of the gate electrode 50 in the Z direction is larger than that of the semiconductor layer 21B. In a plan view viewed from the Z direction, the gate electrode 50 is provided to surround the periphery of each of the columnar portions 22. That is, in a plan view viewed from the Z direction, the gate electrode 50 is provided to surround the periphery of the channel formation region R. The gate electrode 50 includes, for example, polycrystalline silicon (Poly-Si) and is formed of Poly-Si doped with boron (B). B-doped Poly-Si has a high work function among materials that can be used to form a gate electrode. By providing a sufficiently high work function, the threshold voltage of the semiconductor device 10 can be made positive (ie, normally off).

[0030] The gate insulating film 40 is provided on the sidewalls 50c and surface 50a of the gate electrode 50. That is, in the XY plane, the gate insulating film 40 is interposed between the gate electrode 50 and the semiconductor layer 21B. The gate insulating film 40 is made of, for example, silicon oxide (SiO2).

[0031] An insulating layer 46 and a mask insulating film 44 are sequentially stacked in the Z direction on the surface 40a of the gate insulating film 40. The surface 46a of the insulating layer 46 overlaps with the surfaces 22a of the multiple columnar sections 22 in the Z direction and is formed to be approximately flush with the surface 21a of the semiconductor layer 21C. The size of the insulating layer 46 in the Z direction is larger than that of the mask insulating film 44. The insulating layer 46 is formed of, for example, glass containing SiO2 as a main component, SiO2, or the like. The mask insulating film 44 is formed of, for example, SiO2.

[0032] An insulating layer 42 is provided on the bottom surface 50b of the gate electrode 50. The insulating layer 42 is formed of, for example, glass containing SiO2 as a main component, or SiO2. The gate electrodes 50 interposed between the multiple columnar portions 22 are surrounded by the gate insulating film 40 and the insulating layer 42, and are connected to each other in predetermined regions of the semiconductor device 11 different from the region shown in cross section in FIG. 2, and are arranged so as to be able to supply a gate voltage.

[0033] The semiconductor layer 70 is provided between the insulating layer 42 and the second layer 32 of the semiconductor layer 30 in the Z direction, and is provided on the sidewall 21d of the semiconductor layer 21A in the drain region D. In the XY plane, the semiconductor layer 70 abuts the semiconductor layer 21A. A bottom surface 70b of the semiconductor layer 70 overlaps with the bottom surfaces 22b of the multiple columnar portions 22 in the Z direction and is formed to be approximately flush with the bottom surface 21b of the semiconductor layer 21A. The semiconductor layer 70 is electrically connected to the semiconductor layers 20, 21C in the source region S via a metal plug 78, which will be described later.

[0034] The conductivity type of the semiconductor layer 70 is different from the conductivity type of the semiconductor 21 that forms at least the semiconductor layer 21A. The semiconductor layer 70 is formed of, for example, a p-type semiconductor. An example of a p-type semiconductor is GaN doped with p-type impurities. Examples of p-type impurities include magnesium (Mg) and zinc (Zn). Hereinafter, GaN doped with p-type impurities may be referred to as p-GaN. Furthermore, p-GaN with a relatively high impurity concentration may be referred to as p-GaN. + -GaN is described as p - The impurity concentration does not affect the conductivity of the semiconductor.

[0035] In the semiconductor device 11, the sidewalls 21d of the semiconductor layer 21A constituting the drain regions D of the plurality of columnar sections 22 are adjacent to the semiconductor layer 70, and the semiconductor layers 21A and 70 are PN junctioned with each other, thereby forming an SJ structure. - The semiconductor layer 21A is made of GaN and the p +An SJ structure with the semiconductor layer 70 formed of -GaN is provided. The SJ structure with the semiconductor layer 70 supports the depletion layer Em of the semiconductor layer 21A from the radially outer side along the XY plane. This allows the on-resistance to be minimized while ensuring the breakdown voltage of the vertical FET in each of the multiple columnar sections 22, as described above. By reducing the on-resistance per area at the surface 30a of the semiconductor layer 30, the switching frequency can be increased when switching the semiconductor device 11. As a result, the power density of the semiconductor device 11 as a power source is improved, and the performance of the power device is improved. Furthermore, the semiconductor layer 70 may be provided on the sidewall of the second region or on the sidewall of the first region. It may also be provided on the sidewalls of both the first and second regions. By providing the semiconductor layer 70 on the sidewall of the second region with a low impurity concentration, the depletion layer Em can be expanded from the radially outer side along the XY plane, thereby ensuring the breakdown voltage of the FET and reducing the on-resistance.

[0036] Between the gate electrode 50 and the semiconductor layer 20 in the Z direction, an insulating layer 46 and a mask insulating film 44 are sequentially provided in the opposite direction to the Z direction. The surface 44a of the mask insulating film 44 overlaps with the surface 22a of each of the plurality of columnar sections 22 in the Z direction and is formed to be substantially flush with the surface 21a of the semiconductor layer 21C. Adjacent columnar sections 22 in the XY plane are separated by the semiconductor layer 70, the insulating layer 42, the gate insulating film 40, the insulating layer 46, and the mask insulating film 44. Like the insulating layer 42, the insulating layer 46 is formed of, for example, glass containing SiO2 as a main component, or SiO2. The mask insulating film 44 is formed of, for example, SiO2 or silicon nitride (SiN).

[0037] The semiconductor device 11 further includes a metal plug 78 and a conductive layer 80. The metal plug 78 connects the metal layer 12 and the semiconductor layer 70 in the Z direction. A surface 78a of the metal plug 78 abuts the back surface 12b of the metal layer 12. A bottom surface 78b of the metal plug 78 abuts the surface 70a of the semiconductor layer 70. The metal plug 78 penetrates the semiconductor layer 20, the mask insulating film 44, the insulating layer 46, the gate insulating film 40, and the insulating layer 42, which are interposed in the Z direction between the metal layer 12 and the semiconductor layer 70 in a region where the plurality of columnar portions 22 are not formed in the XY plane. The metal plug 78 is electrically connected to each semiconductor layer 21C of the plurality of columnar portions 22 via the semiconductor layer 20 that constitutes the source region S. Therefore, the source voltage supplied from the metal layer 12 to the semiconductor layers 20 and 21C is also supplied to the semiconductor layer 70 via the metal plug 78. The metal plug 78 is made of a conductive material. An example of the conductive material is W. The metal plug 78 corresponds to the "metal conductive layer" in the claims.

[0038] The conductive layer 80 is connected to the gate electrode 50 in a predetermined region in the XY plane where the plurality of columnar sections 22 are not formed, and directly supplies a gate voltage to the gate electrode 50. The conductive layer 80 penetrates in the Z direction through the insulating layer 46 and the mask insulating film 44 that are stacked on the gate electrode 50 in the predetermined region.

[0039] As shown in FIG. 1, in regions other than the region where the plurality of columnar portions 22 are formed in the XY plane, an interlayer insulating layer 200 is appropriately provided, for example, between the metal layers 12 and 60, and between the semiconductor layer 70, the semiconductor layer 20 in the source region S, the plurality of columnar portions 22, etc.

[0040] In the above-described semiconductor device 11, the impurity concentration of the semiconductor layer 21B is set lower than the impurity concentrations of the semiconductor layers 21A and 21C, and no current flows between the drain region D and the source region S unless a positive voltage equal to or greater than the threshold is supplied to the gate electrode 50. When the gate voltage is 0V or when a voltage less than the threshold is supplied to the gate electrode 50, the region Ch of the semiconductor layer 21C is substantially completely depleted. When a positive voltage equal to or greater than the threshold is supplied to the gate electrode 50, a channel region Ch is formed in the semiconductor layer 21B of the channel formation region R adjacent to the gate electrode 50 via the gate insulating film 40. The n forming the semiconductor layer 21C of the source region S + -GaN electrons and the semiconductor layer 21A of the drain region D - Electrons in the -Gan are strongly attracted to region Ch, which becomes a flow path for the electrons, causing a current to flow between the drain region D and the source region S. The size of region Ch of the channel formed in the channel formation region R is controlled by the voltage supplied to the gate electrode 50, and the value of the current flowing between the drain region D and the source region S changes. The current between the drain region D and the source region S is controlled by the gate electrode 50.

[0041] In the semiconductor device 11, as described above, the semiconductor layer 70 is interposed between the semiconductor layers 21A in the XY plane, thereby forming an SJ structure. In the semiconductor device 11, the depletion layer Em extends from the interface between the semiconductor layers 21B and 21A to the p +The -GaN semiconductor layer 70 is formed along the sidewall 21d, separated from the other side of the semiconductor layer 70. Therefore, the interface with a large difference in impurity concentration is wider than in a structure without an SJ structure. Therefore, the electric field strength is lower than the maximum value of the semiconductor device 11 and is substantially constant from the interface between the semiconductor layers 21B and 21A to the interface between the semiconductor layers 21A and 20. Generally, to prevent breakdown in a semiconductor device, the breakdown voltage is set so as not to exceed the maximum value of the electric field strength determined by the semiconductor material. Furthermore, when the horizontal axis represents the position in the Z direction and the vertical axis represents the electric field strength, the breakdown voltage of the semiconductor device is determined by the area of the electric field strength distribution. In the semiconductor device 11, the maximum value of the electric field strength can be reduced while maintaining the area of the electric field strength distribution. Furthermore, in the semiconductor device 11, the carrier concentration can be increased by the amount of the reduction in the maximum electric field strength, resulting in a low on-resistance.

[0042] (Method of manufacturing a semiconductor device) Next, a method for manufacturing the semiconductor device 11 of this embodiment will be described. Each of Figures 3 to 20 is a cross-sectional view showing each step of the method for manufacturing the semiconductor device 11.

[0043] As shown in FIG. 3, first, a GaN crystal is grown on a surface 110a of a substrate 110 for growing GaN crystals by, for example, molecular beam epitaxy (MBE), MOCVD (Metal Organic Chemical Vapor Deposition), or the like. + Crystal growth of GaN is performed to form the semiconductor layer 20. The substrate 110 may be, for example, a sapphire substrate.

[0044] Next, SiO2 is deposited on the surface 20a of the semiconductor layer 20 by, for example, chemical vapor deposition (CVD) or physical vapor deposition (PVD) to form a mask insulating film 44. Subsequently, by, for example, photolithography and etching, only the mask insulating film 44 stacked in the region of the surface 20a of the semiconductor layer 20 where the plurality of columnar sections 22 are to be formed is removed to expose the surface 20a of the semiconductor layer 20 in that region.

[0045] Next, the surface 20a of the semiconductor layer 20 exposed in the previous step is subjected to n-type doping by, for example, MBE. + The semiconductor layer 21C is then crystal-grown with i-GaN to a predetermined height in the Z direction. Then, the surface 121a of the semiconductor layer 21C, i.e., the rear bottom surface, is flattened parallel to the XY plane, and i-GaN is then crystal-grown on the surface 121a by, for example, MBE to a predetermined height in the Z direction, forming the semiconductor layer 21B. Then, the surface 122a of the semiconductor layer 21B, i.e., the rear bottom surface, is flattened, and n-GaN is then crystal-grown on the surface 122a by, for example, MBE. - The semiconductor layer 21A is formed by crystal growth of GaN to a predetermined height in the Z direction. Alternatively, the dopant concentration, for example, the Si concentration, may be varied to successively form the semiconductor layers 21C, 21B, and 21A. That is, in the manufacturing method of the semiconductor device 11, the semiconductor 21 constituting the columnar portion 22 is formed bottom-up in the Z direction from the semiconductor layer 20 that will later become the source region S.

[0046] The surface 123a of the semiconductor layer 21A may have irregularities with respect to the XY plane and does not need to be flattened at the stage shown in FIG. 3. When the semiconductor layers 21C, 21B, and 21A are each grown by MBE, irregularities occur on the surface of each. For this reason, it is preferable to grow each of the semiconductor layers 21C, 21B, and 21A to a sufficient height in the Z direction so that the minimum size in the Z direction of each of the semiconductor layers 21C, 21B, and 21A is equal to or greater than the size in the Z direction of each of the semiconductor layers 21A, 21B, and 21C of the columnar portion 22 shown in FIG.

[0047] Next, a spin-on-glass (SOG) liquid is applied and processed by, for example, spin coating so as to cover the surface 44a of the mask insulating film 44, i.e., the rear bottom surface, and the pillars 25 made of the semiconductor layers 21C, 21B, and 21A, to form an insulating layer 46 made of SiO2 or the like, as shown in FIG. 4. This process brings the sidewall 21r of the semiconductor layer 21B, the sidewalls of the semiconductor layers 21C and 21A, and the surface of the semiconductor layer 21A into contact with the insulating layer 46. The surface 46a of the insulating layer 46 is located further above the tips of the pillars 25 in the Z direction, i.e., forward in the Z direction.

[0048] Next, as shown in FIG. 5, the insulating layer 46 is etched back until the surface 46a reaches the bottom surface 21t of the semiconductor layer 21B of the columnar body 25, ie, reaches a position appropriately further back in the Z direction than the rear surface.

[0049] Next, for example, by atomic layer deposition (ALD), SiO2 is deposited in the form of a film so as to cover the surface 46a of the insulating layer 46 and the exposed sidewalls and surfaces of the pillars 25, thereby forming the gate insulating film 40 as shown in FIG. 6.

[0050] Next, B-doped Poly-Si is deposited in the Z direction on the surface of the gate insulating film 40 stacked on the insulating layer 46, i.e., from the rear bottom surface 40b to a position that completely covers the gate insulating film 40 that covers the pillars 25, to form a precursor layer 52 of the gate electrode 50 as shown in FIG. 7. The B doping may be achieved by implanting boron ions into the Poly-Si and then thermally diffusing them. Next, the precursor layer 52 is etched back until the surface 52a reaches the surface 21p of the semiconductor layer 21B of the pillars 25, i.e., a position that is suitably forward in the Z direction from the rear bottom surface, to form the gate electrode 50 as shown in FIG.

[0051] Next, the surface of the gate electrode 50, i.e., the gate insulating film 40 exposed in the Z direction from the rear bottom surface 50b, is removed by wet etching using, for example, a chemical solution, as shown in Fig. 9. This process forms the gate insulating film 40 surrounding the sidewall 50c and surface 50a of the gate electrode 50.

[0052] Next, by using, for example, lithography and etching, a through-hole 54 is formed in the gate electrode 50 in a region in the XY plane where the multiple columnar portions 22 are not formed. The through-hole 54 penetrates only the gate electrode 50 in the Z direction. At the bottom of the through-hole 54, the surface of the gate insulating film 40, i.e., the rear bottom surface 40b, is exposed.

[0053] Next, an SOG liquid is applied and processed to fill the through-holes 54 and cover the exposed columns 25 that protrude in the Z direction beyond the bottom surfaces 50b of the gate electrodes 50, thereby forming an insulating layer 42 as shown in Fig. 11. Subsequently, the insulating layer 42 is subjected to a chemical mechanical polishing (CMP) method or etched back as shown in Fig. 12 until the surface of the insulating layer 42, i.e., the rear bottom surface 42b, reaches a position that is moderately forward in the Z direction relative to the bottom surface 50b of the gate electrode 50, i.e., moderately higher than the gate electrode 50. At this time, the bottom surface 42b of the insulating layer 42 is made flat.

[0054] Next, as shown in FIG. 13, a p + GaN is deposited to form the semiconductor layer 70.

[0055] Next, the front portion of the semiconductor layer 70 in the Z direction is removed by thermal etching using, for example, phosphoric acid. As shown in FIG. 14, the surface of the semiconductor layer 70, i.e., the rear bottom surface 70b, is aligned with the rearmost position in the Z direction of the uneven surface of the semiconductor layer 21A and moderately forward in the Z direction from the surface 21p of the semiconductor layer 21B, i.e., a position higher than the semiconductor layer 21B. In this process, the bottom surface 70b of the semiconductor layer 70 is aligned with the bottom surfaces 22b of the multiple columnar portions 22 and the bottom surface of the semiconductor layer 21A in the Z direction, and is made flush with the bottom surface 22b. This process forms multiple columnar portions 22 protruding in the Z direction from the bottom surface 20b of the semiconductor layer 20.

[0056] Next, as shown in FIG. 15, the entire flat surface consisting of the bottom surfaces 22b of the plurality of columnar sections 22 and the bottom surface 70b of the semiconductor layer 70 is doped with n-type SiO 2 by, for example, MBE. - The GaN is grown to a predetermined height in the Z direction to form the second layer 32 of the semiconductor layer 30. Subsequently, n-type GaN is grown on the surface of the second layer 32, i.e., the rear bottom surface 32b, by, for example, MBE. + The first layer 31 of the semiconductor layer 30 is formed by crystal growth of the -GaN to a predetermined height in the Z direction.

[0057] Next, an adhesive (not shown) is applied to the surface of the first layer 31 of the semiconductor layer 30, i.e., the rear bottom surface 31b, and a metal layer 60 is bonded to the bottom surface 31b via the adhesive, as shown in Fig. 16. The adhesive may be, for example, an ultraviolet curable resin or a thermosetting resin, but is not particularly limited as long as it can satisfactorily bond the metal layer 60 to the bottom surface 30b of the semiconductor layer 30. For example, instead of an adhesive, a metal for bonding may be deposited.

[0058] Next, the substrate 110 is removed from the stacked structure 140, which includes the substrate 110, semiconductor layers 20, 21C, 21B, and 21A, mask insulating film 44, insulating layer 46, gate insulating film 40, gate electrode 50, insulating layer 42, semiconductor layers 70 and 30, and metal layer 60, which were fabricated in the previous process. Specifically, as shown in FIG. 17 , the stacked structure 140 is inverted in the Z direction, and a laser lift-off (LLO) process, for example, is performed. In the LLO process, laser light HL from a high-power laser light source (not shown) is irradiated from behind the substrate 110 in the Z direction, and the substrate 110 is peeled off from the surface 20a of the semiconductor layer 20, as shown in FIG. 18 . When the substrate 110 is a sapphire substrate, a krypton fluoride (KrF) excimer laser is suitable as the high-power laser light source. When a KrF excimer laser is used, the center wavelength of the laser light HL is approximately 248 nm.

[0059] Next, as shown in FIG. 19 , through-holes 56 are formed in regions in the XY plane where the metal plugs 78 shown in FIGS. 1 and 2 are to be formed, but where the multiple columnar portions 22 are not formed. The through-holes 56 reach the surface 70a of the semiconductor layer 70 in the Z direction from the surface 20a of the semiconductor layer 20 exposed by peeling off the substrate 110. The through-holes 56 can be formed, for example, by lithography and dry etching. Next, a conductive material such as W is deposited in the through-holes 56 and behind the through-holes 56 in the Z direction, for example, by CVD. The conductive layer is then etched back until the surface of the conductive layer made of the deposited conductive material is flush with the surface 20a of the semiconductor layer 20. This process forms the metal plugs 78, as shown in FIG. 20 .

[0060] Next, in a region in the XY plane where the plurality of columnar portions 22 are not formed and where the conductive layer 80 shown in FIGS. 1 and 2 will be formed, the semiconductor layer 20, mask insulating film 44, insulating layer 46, and gate insulating film 40 in a region 58 indicated by a dashed line in FIG. 20 are removed to form an opening. The gate electrode 50 is exposed at the bottom of the opening. Next, although not shown, a conductive material such as W is deposited in the opening and behind the opening in the Z direction to form the conductive layer 80.

[0061] Next, an adhesive (not shown) is applied to the surface of the semiconductor layer 20 in the region overlapping with the plurality of columnar portions 22 in the XY plane and to the surface 78a of the metal plug 78, and the metal layer 12 is bonded via the adhesive. Note that this step may be performed after the formation of the metal plug 78 and before the formation of the conductive layer 80.

[0062] Furthermore, although not shown, in regions other than the region where the multiple columnar portions 22 are formed in the XY plane, the interlayer insulating layer is removed in the Z direction from the gate electrode 50 in the region where the gate conductive layer contacting the gate electrode 50 is disposed, for example, by lithography and dry etching to form through-holes. Furthermore, the interlayer insulating layer is removed in the Z direction from the semiconductor layer 20 in the region where the source conductive layer contacting the semiconductor layer 20 in the source region S is disposed, for example, by lithography and CNT etching to form through-holes. Next, W is deposited in each through-hole and behind the through-hole in the Z direction, for example, by CVD, to form gate conductive layers and source conductive layers. The gate conductive layers and source conductive layers are then etched back until their surfaces are flush with the surface 20a of the semiconductor layer 20. A gate metal layer and a source metal layer are bonded to the surfaces of the gate conductive layer and source conductive layer using an adhesive. This process can be performed at an appropriate timing depending on the balance with the above-mentioned processes. Alternatively, in an area other than the area where the plurality of columnar sections 22 are formed in the XY plane, a wire bonding may be formed to contact, for example, the gate electrode 50. Also, a wire bonding may be formed on the metal layer 12.

[0063] By carrying out the above-mentioned steps, the main structure of the semiconductor device 11 shown in Figures 1 and 2 is manufactured. Although not shown, post-processing is carried out as necessary to complete the semiconductor device 11.

[0064] (Action and effect) The semiconductor device 11 of the present embodiment described above includes a plurality of pillar-shaped portions 22 made of a semiconductor 21. Each of the plurality of pillar-shaped portions 22 has a source region S, a drain region D, a channel formation region R, a gate electrode 50, and a semiconductor layer 70. The channel formation region R includes a channel region (channel region) Ch formed between the source region S and the drain region D in the Z direction. The gate electrode 50 is provided on a sidewall 21r of the semiconductor layer 21B that forms the channel formation region R, via a gate insulating film 40. The semiconductor layer 70 is provided on a sidewall 21d of the semiconductor layer 21A that forms the drain region D. The conductivity type of the semiconductor layer 70 is different from the conductivity type of the semiconductor 21 of the semiconductor layer 21A.

[0065] In the semiconductor device 11 of this embodiment, a vertical FET with a GAA structure is formed by multiple pillar-shaped portions 22 and gate electrodes 50 adjacent to the channel formation region R via a gate insulating film 40. In the semiconductor device 11, the pillar-shaped portions 22 are formed with an extremely fine pitch of, for example, 0.5 μm or less in the XY plane. Furthermore, by arranging the semiconductor layer 70 adjacent to the semiconductor layer 21A of each of the drain regions D of the multiple pillar-shaped portions 22 in a direction along the XY plane, i.e., in the lateral direction, an SJ structure is formed, and the breakdown voltage of the multiple pillar-shaped portions 22 is supported laterally. Therefore, the semiconductor device 11 of this embodiment can achieve significantly lower on-resistance than multiple pillar-shaped portions 22 not including the semiconductor layer 70.

[0066] The plurality of pillars 22 of the semiconductor device 11 of this embodiment are formed from the semiconductor layer 20 in a bottom-up manner, rather than by a top-down manufacturing method using a dry etching process as in conventional semiconductor devices. + -n in the Z direction from the bottom surface 20b of the semiconductor layer 20 made of GaN + -GaN, i-GaN, n - By growing GaN in a bottom-up manner, the base end does not spread out more than the tip end as in conventional semiconductor nanowires, and it is possible to form columnar portions 22 with fine pitch and high crystallinity.

[0067] In the semiconductor device 11 of this embodiment, the gate electrode 50 is made of poly-Si and doped with Br. Specifically, the gate electrode 50 is formed of poly-Si doped with Br. Furthermore, the semiconductor 21 of the semiconductor layers 21C, 21A, and 21B constituting the source region S, drain region D, and channel formation region R of each of the plurality of pillar-shaped portions 22 is GaN. As described above, in the plurality of pillar-shaped portions 22 having a GAA structure, the gate electrode 50 is formed of a material having a high work function, thereby increasing the drive voltage of the semiconductor device 11 and reliably realizing a normally-off state. In particular, the use of p-type poly-Si facilitates normally-off state. While there is a trade-off between high current drive capability and normally-off state, the semiconductor device 11 of this embodiment uses poly-Si doped with Br as the material for the gate electrode 50, thereby achieving both high current drive capability and normally-off state.

[0068] Furthermore, in the semiconductor device 11 of this embodiment, the semiconductor layer 70 is electrically connected to the source region S, and is also electrically connected to the semiconductor layers 20 and 21C that constitute the source region S. According to the semiconductor device 11 of this embodiment, a source voltage is supplied to the semiconductor layer 70, and the semiconductor layer 21A in the drain region D of the columnar portion 22 supports the depletion layer Em, thereby obtaining a breakdown voltage.

[0069] Furthermore, in the semiconductor device 11 of this embodiment, the semiconductor layer 20 is connected to the semiconductor layer 21C that constitutes the source region S of each of the plurality of columnar portions 22. According to the semiconductor device 11 of this embodiment, in the source region S, the semiconductor layer 20 is interposed between the plurality of columnar portions 22 that have small diameters in the XY plane and the metal layer 12 that extends in the XY plane, thereby suppressing an increase in contact resistance in the connection between the semiconductor layer 21C and the conductive layer that is the source-side contact terminal, i.e., the metal layer 12, thereby preventing a decrease in performance and ensuring good operation.

[0070] In the semiconductor device 11 of this embodiment, the semiconductor layer 30 is connected to the semiconductor layer 21A that constitutes the drain region D of each of the plurality of columnar sections 22. Therefore, according to the semiconductor device 11 of this embodiment, in the drain region D as well as the source region S, the semiconductor layer 30 is interposed between the semiconductor layer 21A of the plurality of columnar sections 22 that have small diameters in the XY plane and the metal layer 60 that extends in the XY plane, thereby suppressing an increase in contact resistance in the connection between the semiconductor layer 21A and the conductive layer that is the contact terminal on the drain side, i.e., the metal layer 60, and preventing a decrease in performance.

[0071] In the semiconductor device 11 of this embodiment, the semiconductor 21 and the semiconductor layer 20 each have an n-type conductivity, and the semiconductor layer 70 has a p-type conductivity. This allows the channel region Ch in each of the multiple columnar portions 22 to be almost completely depleted, thereby increasing the charge transfer speed. As a result, the switching speed and operating performance of the semiconductor device 11 can be improved.

[0072] In the semiconductor device 11 of this embodiment, the metal layer 12 is connected to the semiconductor layer 20 on the source side. According to the semiconductor device 11 of this embodiment, it is possible to effectively suppress an increase in contact resistance between the semiconductor layer 21C and the metal layer 12, which is a highly conductive contact terminal on the source side. In the semiconductor device 11 of this embodiment, the metal layer 60 is connected to the semiconductor layer 30 on the drain side. The semiconductor layer 30 has a stacked structure of a first layer 31 and a second layer 32. The semiconductor layer 21C and the second layer 32 are both n - -GaN, and the first layer 31 is n + -GaNd is formed. That is, the conductivity increases in the order of semiconductor layer 21C, second layer 32, first layer 31, and metal layer 60. As a result, according to the semiconductor device 11 of this embodiment, it is possible to effectively suppress an increase in contact resistance between the semiconductor layer 21A and metal layer 12, which is a highly conductive contact terminal on the drain side. Furthermore, since the metal layers 12 and 60 function as the element substrate and counter substrate of the semiconductor device 11, it is possible to realize a thin and lightweight semiconductor device 11.

[0073] In the semiconductor device 11 of this embodiment, the n - The impurity concentration of the semiconductor layer 21A made of GaN is p + The semiconductor layer 70 made of GaN and the n-type semiconductor layer 30 + - is lower than that of the first layer 31 made of GaN. Therefore, the transfer of charges due to the PN junction between the semiconductor layer 21A and the semiconductor layer 70 is prevented from being directly connected to the first layer 31 of the semiconductor layer 30, and the occurrence of breakdown in the semiconductor device 11 can be prevented.

[0074] Furthermore, in the semiconductor device 11 of this embodiment, the source region S is connected to the metal layer 12 and the semiconductor layer 70 by a metal plug 78 that penetrates the semiconductor layer 20 in the Z direction. According to the semiconductor device 11 of this embodiment, the source voltage is smoothly supplied from the metal layer 12 to the semiconductor layers 20 and 70 via the metal plug 78, and the depletion layer Em is supported by the semiconductor layer 21A in the drain region D of the columnar section 22, thereby obtaining a breakdown voltage. Compared to connecting the source region S to the metal layer 12 and the semiconductor layer 70 by a plug or the like made of semiconductor, the metal plug 78 can be easily and stably manufactured using etching and deposition processes. Therefore, the operational reliability of the semiconductor device 11 can be improved.

[0075] Although the preferred embodiments of the present invention have been described in detail above, the present invention is not limited to the specific embodiments, and various modifications and variations are possible within the scope of the gist of the present invention as set forth in the claims. Furthermore, the components of multiple embodiments can be combined as appropriate.

[0076] Furthermore, although the semiconductor device according to the present invention can be applied to power devices such as inverters as described in the above embodiments, the use of the semiconductor device according to the present invention is not limited to power devices. For example, the semiconductor device according to the present invention may be mounted on a moving object such as a vehicle such as an automobile or an airplane, and can be applied to semiconductor devices and switching devices that require ultra-low on-resistance. In the semiconductor device according to the present invention, the material of each component can be changed according to the use of the semiconductor device as long as it does not interfere with the operation of the multiple columnar portions 22 as FETs or the effects of the SJ structure.

[0077] For example, in the semiconductor device according to the present invention, the semiconductor forming the source region S, drain region D, and channel formation region R of each of the multiple pillars is not limited to n-GaN or GaN. If permitted for the intended use of the semiconductor device according to the present invention, the semiconductor for the pillars may be Si, gallium arsenide (GaAs), silicon carbide (SiC), or the like. It is preferable that the semiconductor for the pillars exhibit electrical characteristics appropriate for each region of the FET by varying the impurity concentration.

[0078] For example, when the semiconductor device according to the present invention is used in a power device such as an inverter, since the semiconductor forming each of the plurality of pillar-shaped portions is n-GaN, the gate electrode is preferably formed of Br-doped poly-Si. However, if the semiconductor forming the FET of the semiconductor device according to the present invention is SiC and the semiconductor is acceptable for the intended use of the semiconductor device, the gate electrode may be formed of, for example, Al or W, or a conductive material containing these metals. Even in this case, it is preferable that the gate electrode has a high work function relative to the semiconductor forming the pillar-shaped portions.

[0079] The semiconductor device according to the aspect of the present invention may have the following configuration. A semiconductor device according to one embodiment of the present invention includes a plurality of pillar-shaped portions made of a semiconductor. Each of the pillar-shaped portions has a source region, a drain region, and a channel formation region located between the source region and the drain region. The semiconductor device according to one embodiment of the present invention further includes a gate electrode provided on a sidewall of the channel formation region via an insulating layer to control current between the source region and the drain region, and a first semiconductor layer provided on a sidewall of the drain region. The conductivity type of the first semiconductor layer is different from the conductivity type of the semiconductor forming the drain region.

[0080] In the semiconductor device according to one aspect of the present invention, the gate electrode may be made of polycrystalline silicon. In the semiconductor device according to one aspect of the present invention, the gate electrode may be doped with boron.

[0081] In the semiconductor device according to one aspect of the present invention, the semiconductor may be gallium nitride.

[0082] In the semiconductor device according to one aspect of the present invention, the first semiconductor layer may be electrically connected to the source region.

[0083] In the semiconductor device according to one aspect of the present invention, the second semiconductor layer may be connected to the source region of each of the plurality of columnar portions.

[0084] In the semiconductor device according to one aspect of the present invention, the conductivity type of each of the semiconductor and the second semiconductor layer may be n-type, and the conductivity type of the first semiconductor layer may be p-type.

[0085] In the semiconductor device according to one aspect of the present invention, a metal layer may be connected to the second semiconductor layer.

[0086] In the semiconductor device according to one aspect of the present invention, the source region, the metal layer, and the first semiconductor layer may be connected by a metal plug that penetrates the second semiconductor layer.

[0087] In one embodiment of the semiconductor device of the present invention, the drain region includes a first region and a second region located between the first region and the channel formation region, and the impurity concentration of the second region may be lower than the impurity concentration of the first region.

[0088] In the semiconductor device according to one aspect of the present invention, a first semiconductor layer may be provided on a sidewall of the second region. [Explanation of symbols]

[0089] 11...semiconductor device, 21...semiconductor, 22...columnar portion, 20...semiconductor layer (second semiconductor layer), 40...gate insulating film, 50...gate electrode, 60...metal layer, 70...semiconductor layer (first semiconductor layer), D...drain region, R...channel formation region, S...source region.

Claims

1. a plurality of semiconductor pillars; Each of the plurality of columnar portions is A source region; a drain region; a channel forming region located between the source region and the drain region; and a gate electrode provided on a side wall of the channel formation region via an insulating layer, the gate electrode controlling a current between the source region and the drain region; a first semiconductor layer provided on a sidewall of the drain region; Equipped with the conductivity type of the first semiconductor layer is different from the conductivity type of the semiconductor forming the drain region, a second semiconductor layer connected to the source region of each of the plurality of columnar portions; the source region, the drain region, and the second semiconductor layer each have an n-type conductivity; The conductivity type of the first semiconductor layer is p-type. Semiconductor device.

2. the gate electrode is made of polycrystalline silicon; The semiconductor device according to claim 1 .

3. the gate electrode is doped with boron; The semiconductor device according to claim 2 .

4. the semiconductor is gallium nitride; The semiconductor device according to claim 1 .

5. the first semiconductor layer is electrically connected to the source region; The semiconductor device according to claim 1 .

6. a metal layer connected to the second semiconductor layer; The semiconductor device according to claim 1 .

7. The metal layer and the first semiconductor layer are connected by a metal conductive layer that penetrates the second semiconductor layer. The semiconductor device according to claim 6.

8. A third semiconductor layer is connected to the drain region on the opposite side of the channel formation region, the third semiconductor layer is made of an n-type semiconductor and includes a first layer and a second layer located between the first layer and the columnar portion, a concentration of n-type impurities in the second layer is lower than a concentration of n-type impurities in the first layer; The semiconductor device according to claim 1 .

9. the drain region is made of an n-type semiconductor and includes a first region and a second region located between the first region and the channel formation region; the drain region has an n-type impurity concentration lower than the n-type impurity concentration of the first layer; The concentration of n-type impurities in the second region is lower than the concentration of n-type impurities in the first region. The semiconductor device according to claim 8 .

10. The first semiconductor layer is provided on a sidewall of the second region. The semiconductor device according to claim 9 .

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