Semiconductor device and method for manufacturing a semiconductor device

Abstract

To provide a semiconductor device capable of obtaining stable characteristics, and a method for manufacturing the semiconductor device.SOLUTION: A semiconductor device includes first to second semiconductor layers and first to third electrodes, a conductive part, and an insulating part. The second semiconductor layer is located on the first semiconductor layer. The first electrode is located on the second semiconductor layer. The first electrode includes an electrode part and an electrode extension part. The electrode extension part extends from an upper end portion of the electrode part in a second direction perpendicular to a first direction, the first direction being from the first semiconductor layer toward the second semiconductor layer. The second electrode is located on the second semiconductor layer and is separated from the first electrode in the second direction. The conductive part is in contact with an upper surface of the second semiconductor layer, and is positioned between the first electrode and the second electrode to be in contact with the first electrode. The insulating part is located on the conductive part and is positioned between the conductive part and the electrode extension part. The third electrode is positioned above the second semiconductor layer with an insulating film part interposed and is positioned between the first electrode and the second electrode.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] Embodiments of the present invention relate to a semiconductor device and a method for manufacturing a semiconductor device.

Background Art

[0002] In semiconductor devices such as transistors using nitride semiconductors, changes in characteristics such as an increase in on-resistance may occur due to operations such as repeated switching.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] The problem to be solved by the present invention is to provide a semiconductor device and a method for manufacturing a semiconductor device capable of obtaining stable characteristics.

Means for Solving the Problems

[0005] The semiconductor device according to the embodiment includes a first semiconductor layer, a second semiconductor layer, a first electrode, a second electrode, a conductive portion, an insulating portion, and a third electrode. The first semiconductor layer includes a nitride semiconductor. The second semiconductor layer is provided on the first semiconductor layer and includes a nitride semiconductor. The first electrode is provided on the second semiconductor layer. The first electrode includes an electrode portion and an electrode extension portion. The electrode portion is in contact with the second semiconductor layer. The electrode extension portion extends from the upper end of the electrode portion in a second direction perpendicular to a first direction toward the second semiconductor layer. The second electrode is provided on the second semiconductor layer and is separated from the first electrode in the second direction. The conductive portion is in contact with the upper surface of the second semiconductor layer, is located between the first electrode and the second electrode, and is in contact with the first electrode. The length along the second direction from the electrode portion to the end of the conductive portion on the second electrode side is longer than the length along the second direction from the electrode portion to the end of the electrode extension portion on the second electrode side. The insulating portion is provided on the conductive portion and is located between the conductive portion and the electrode extension portion. The third electrode is located above the second semiconductor layer via an insulating film portion and is located between the first electrode and the second electrode. [Brief explanation of the drawing]

[0006] [Figure 1] Figure 1 is a schematic cross-sectional view illustrating a semiconductor device according to an embodiment. [Figure 2] Figure 2 is a schematic plan view illustrating a semiconductor device according to an embodiment. [Figure 3] Figures 3(a) to 3(c) are schematic cross-sectional views illustrating a semiconductor device according to a reference example. [Figure 4] Figures 4(a) and 4(b) are schematic cross-sectional views illustrating semiconductor devices. [Figure 5] Figure 5 is a schematic plan view illustrating a semiconductor device according to a modified embodiment. [Figure 6] Figure 6 is a schematic plan view illustrating a semiconductor device according to a modified embodiment. [Figure 7]Figure 7 is a schematic plan view illustrating a semiconductor device according to a modified embodiment. [Figure 8] Figure 8 is a schematic plan view illustrating a semiconductor device according to a modified embodiment. [Figure 9] Figures 9(a) to 9(d) are schematic cross-sectional views illustrating the manufacturing process of a semiconductor device according to an embodiment. [Figure 10] Figures 10(a) to 10(d) are schematic cross-sectional views illustrating the manufacturing process of a semiconductor device according to an embodiment. [Modes for carrying out the invention]

[0007] Each embodiment of the present invention will be described below with reference to the drawings. Drawings are schematic or conceptual, and the relationships between the thickness and width of each part, as well as the ratios of the sizes of different parts, are not necessarily identical to those of reality. Even when representing the same part, the dimensions and ratios may be depicted differently in different drawings. In this specification and in each figure, elements similar to those already described are denoted by the same reference numerals, and detailed explanations are omitted as appropriate.

[0008] Figure 1 is a schematic cross-sectional view illustrating a semiconductor device according to an embodiment. Figure 2 is a schematic plan view illustrating a semiconductor device according to an embodiment. Figure 1 corresponds to the cross-section along line AA shown in Figure 2. Figures 1 and 2 illustrate a HEMT (High Electron Mobility Transistor) as an example of a semiconductor device 100 according to the embodiment. As shown in Figure 1, the semiconductor device 100 includes a first semiconductor layer 11, a second semiconductor layer 12, a first electrode 21, a second electrode 22, a third electrode 23, an insulating layer 30, and a conductive portion 50. The semiconductor device 100 further includes a wiring layer 41 (first wiring layer) and a wiring layer 42. Note that in Figure 2, some parts such as the wiring layer 41, wiring layer 42, and insulating layer 30 are omitted from the illustration.

[0009] In describing the embodiments, the XYZ Cartesian coordinate system is used. The direction from the first semiconductor layer 11 to the second semiconductor layer 12 is defined as the Z direction (first direction). The two directions perpendicular to the Z direction and mutually orthogonal are defined as the X and Y directions. For explanatory purposes, the direction from the first semiconductor layer 11 to the second semiconductor layer 12 may be referred to as "up," and the opposite direction as "down." These directions are based on the relative positional relationship between the first semiconductor layer 11 and the second semiconductor layer 12 and are independent of the direction of gravity.

[0010] The first semiconductor layer 11 contains a nitride semiconductor. The second semiconductor layer 12 is provided on top of the first semiconductor layer 11 and is in contact with the first semiconductor layer 11. The second semiconductor layer 12 contains a nitride semiconductor. The first semiconductor layer 11 and the second semiconductor layer 12 form, for example, a heterojunction.

[0011] The first electrode 21 is, for example, a drain electrode. The first electrode 21 is provided on a portion of the second semiconductor layer 12. The first electrode 21 is in ohmic contact with the upper surface of the second semiconductor layer 12 and is electrically connected to the second semiconductor layer 12.

[0012] The first electrode 21 includes a first electrode portion 21e and a first electrode extension portion 21f. The lower end of the first electrode portion 21e is in contact with the upper surface of the second semiconductor layer 12. The first electrode extension portion 21f extends from the upper end of the first electrode portion 21e toward the second electrode 22 along the X direction. The first electrode portion 21e and the first electrode extension portion 21f may be, for example, a single conductive layer (metal layer) integrally formed from the same material.

[0013] The conductive portion 50 is provided on the second semiconductor layer 12 and is in contact with the upper surface 12u of the second semiconductor layer 12. The conductive portion 50 may be in ohmic contact with the second semiconductor layer 12 or may not be in ohmic contact (for example, it may be a Schottky contact). The conductive portion 50 is located between the first electrode 21 and the second electrode 22 and is in contact with the second electrode 22. More specifically, as shown in FIG. 1, a part of the conductive portion 50 is provided between the first electrode portion 21e and the second semiconductor layer 12 and is covered by the first electrode portion 21e. That is, a part of the first electrode portion 21e is in contact with the upper surface 50s of a part of the conductive portion 50. Also, in this example, as shown in FIG. 2, the conductive portion 50 extends in the Y direction along the first electrode 21.

[0014] As shown in FIG. 1, the conductive portion 50 extends from the first electrode portion 21e toward the second electrode 22 side more than the first electrode extension portion 21f. That is, the length L1 (the length along the X direction from the first electrode portion 21e to the end portion 50x on the second electrode 22 side of the conductive portion 50) is longer than the length L2 (the length along the X direction from the first electrode portion 21e to the end portion 21fx on the second electrode 22 side of the first electrode extension portion 21f). The end portion 21fx of the first electrode extension portion 21f is aligned (overlaps) with the conductive portion 50 in the Z direction.

[0015] The wiring layer 41 is provided on the first electrode 21 and is electrically connected to the first electrode 21. The wiring layer 41 includes a wiring portion 41e (the first wiring portion) and a wiring extension portion 41f (the first wiring extension portion). The lower end portion of the wiring portion 41e is in contact with the upper end portion of the first electrode portion 21e. The wiring extension portion 41f extends from the upper end portion of the wiring portion 41e toward the second electrode 22 side along the X direction. The wiring portion 41e and the wiring extension portion 41f may be, for example, a single conductive layer (metal layer) integrally formed of the same material.

[0016] In this example, the wiring extension 41f extends further from the wiring portion 41e towards the second electrode 22 than the first electrode extension 21f. For example, the length L3 (the length along the X direction from the first electrode portion 21e to the end 41fx of the wiring extension 41f on the second electrode 22 side) is longer than the length L2 mentioned above. Also, for example, the conductive portion 50 extends further from the first electrode portion 21e towards the second electrode 22 than the wiring extension 41f. For example, the length L1 mentioned above is longer than the length L3. The end 41fx of the wiring extension 41f aligns with the conductive portion 50 in the Z direction, but not with the first electrode extension 21f.

[0017] The second electrode 22 is, for example, a source electrode. The second electrode 22 is provided on a portion of the second semiconductor layer 12. The second electrode 22 is separated from the first electrode 21 in the X direction. The second electrode 22 is in ohmic contact with the upper surface of the second semiconductor layer 12 and is electrically connected to the second semiconductor layer 12.

[0018] For example, the second electrode 22 includes a second electrode portion 22e and a second electrode extension portion 22f. The lower end of the second electrode portion 22e is in contact with the upper surface of the second semiconductor layer 12. The second electrode extension portion 22f extends from the upper end of the second electrode portion 22e toward the first electrode 21 along the X direction. The second electrode portion 22e and the second electrode extension portion 22f may be, for example, a single conductive layer (metal layer) integrally formed from the same material.

[0019] The wiring layer 42 is provided on the second electrode 22 and is electrically connected to the second electrode 22. The wiring layer 42 (second wiring layer) includes a wiring portion 42e (second wiring portion) and a wiring extension portion 42f (second wiring extension portion). The lower end of the wiring portion 42e is in contact with the upper end of the second electrode portion 22e. The wiring extension portion 42f extends from the upper end of the wiring portion 42e toward the first electrode 21 along the X direction. The wiring portion 42e and the wiring extension portion 42f may be, for example, a single conductive layer (metal layer) integrally formed from the same material.

[0020] The wiring extension portion 42f extends further from the wiring portion 42e toward the first electrode 21 than the second electrode extension portion 22f, and covers the second electrode 22. In other words, in the X direction, the end portion 42fx of the wiring extension portion 42f on the first electrode 21 side is located between the end portion 22fx of the second electrode extension portion 22f on the first electrode 21 side and the first electrode 21. The wiring extension 42f extends further toward the first electrode 21 than the third electrode 23, covering the third electrode 23, the conductive member 61, and the conductive member 62. In other words, in the X direction, the end 42fx of the wiring extension 42f is located between the third electrode 23 and the first electrode 21. The wiring extension 42f functions, for example, as a field plate electrode.

[0021] The third electrode 23 is, for example, a gate electrode. The third electrode 23 is located above the second semiconductor layer 12 via an insulating film portion 31a. That is, an insulating film portion 31a is provided on the second semiconductor layer 12, and the third electrode 23 is provided on the insulating film portion 31a. The third electrode 23 is insulated from the second semiconductor layer 12 by the insulating film portion 31a. The third electrode 23 is located between the second electrode 22 and the first electrode 21.

[0022] The third electrode 23 is positioned closer to the second electrode 22 than to the first electrode 21. That is, the distance between the third electrode 23 and the first electrode 21 is longer than the distance between the third electrode 23 and the second electrode 22.

[0023] In this example, a conductive member 61 is provided above the third electrode 23. The conductive member 61 is electrically connected to the third electrode 23 and covers the third electrode 23. A conductive member 62 is provided between the conductive member 61 and the first electrode 21. The conductive member 62 is electrically connected to the second electrode 22 by, for example, a connection (not shown). The conductive members 61 and 62 function, for example, as field plate electrodes.

[0024] The third electrode 23 is insulated from the first electrode 21 and the second electrode 22 by the insulating layer 30. In this example, the insulating layer 30 includes a first insulating film 31 provided on the second semiconductor layer 12, a second insulating film 32 provided on the first insulating film 31, and a third insulating film 33 provided on the second insulating film 32. Thus, the insulating layer 30 may have a laminated structure.

[0025] The first insulating film 31 and the second insulating film 32 are provided between the first electrode portion 21e and the second electrode portion 22e. The aforementioned insulating film portion 31a is a part of the first insulating film 31. The third electrode 23 is provided on the first insulating film 31. A part of the second insulating film 32 is provided on a part of the conductive portion 50. The conductive member 61, the conductive member 62, the first electrode extension portion 21f, and the second electrode extension portion 22f are provided on the second insulating film 32. The third insulating film 33 is provided between the wiring portion 41e and the wiring portion 42e and covers the conductive member 61, the conductive member 62, the first electrode extension portion 21f, and the second electrode extension portion 22f. The wiring extension portion 41f and the wiring extension portion 42f are provided on the third insulating film 33.

[0026] As shown in Figure 1, the semiconductor device 100 is provided with a first insulating portion 30a and a second insulating portion 30b. The first insulating portion 30a and the second insulating portion 30b are parts of the insulating layer 30. More specifically, in this example, the first insulating portion 30a is part of the second insulating film 32, and the second insulating portion 30b is part of the third insulating film 33.

[0027] The first insulating portion 30a is a portion provided on a part of the conductive portion 50. The first insulating portion 30a is in contact with the side surface of the first electrode portion 21e and the upper surface of the conductive portion 50. A part of the first insulating portion 30a is located between the conductive portion 50 and the first electrode extension portion 21f. The second insulating portion 30b is in contact with the side surface of the wiring portion 41e, the upper surface of the first electrode extension portion 21f and the upper surface of the first insulating portion 30a. The second insulating portion 30b is located between the wiring extension portion 41f and the first insulating portion 30a.

[0028] On top of the wiring layer 41, wiring layer 42, and insulating layer 30, an additional insulating layer 35 is provided.

[0029] An example of the material of each element of the semiconductor device 100 will be described. The first semiconductor layer 11 contains, for example, Al x1 Ga 1-x1 N (0 ≤ x1 < 1). The composition ratio x1 of Al in the first semiconductor layer 11 is, for example, 0 or more and 0.01 or less. The first semiconductor layer 11 may be, for example, GaN. The second semiconductor layer 12 contains, for example, Al x2 Ga 1-x2 N (x1 < x2 < 1). The composition ratio x2 of Al in the second semiconductor layer 12 is, for example, 0.1 or more and 0.4 or less. The insulating layer 30 (each of the first insulating film 31, second insulating film 32, and third insulating film 33) and the insulating layer 35 contain at least one of silicon nitride and silicon oxide. The first electrode 21 contains, for example, at least one selected from the group consisting of Ti and Al. The second electrode 22 contains, for example, at least one selected from the group consisting of Ti and Al. The wiring layer 41 and the wiring layer 42 contain, for example, at least one selected from the group consisting of Ti, Al, Au, and W. The third electrode 53 contains, for example, at least one selected from the group consisting of Al, Ti, TiN, TiW, WN, Pt, Ni, In, and Au. The conductive members 61 and 62 contain, for example, at least one selected from the group consisting of Al, Cu, Au, and Ag. The conductive portion 50 contains, for example, at least one selected from the group consisting of Al, Ti, TiN, TiW, WN, Pt, Ni, In, and Au. The conductive portion 50 is, for example, a metal layer. The material of the conductive portion 50 may be different from, for example, the material of the first electrode 21 (first electrode portion 21e). For example, the electrical resistivity (Ω·cm) of the first electrode 21 may be lower than that of the conductive portion 50. The same material as that of the first electrode 21 may be used for the conductive portion 50.

[0030] The operation of the semiconductor device 100 will be described. A positive voltage is applied to the first electrode 21 relative to the second electrode 22. For example, a two-dimensional electron gas (2DEG) is generated near the interface between the first semiconductor layer 11 and the second semiconductor layer 12 within the first semiconductor layer 11. By controlling the voltage of the third electrode 23 with respect to the voltage of the second electrode 22, the concentration of the two-dimensional electron gas below the third electrode 23 can be controlled. For example, when the voltage of the third electrode 23 is above a threshold (e.g., 0V), a two-dimensional electron gas is generated below the third electrode 23. This results in an ON state where electrons flow from the second electrode 22 through the first semiconductor layer 11 to the first electrode 21. When the voltage of the third electrode 23 is less than a threshold (e.g., negative), the concentration of the two-dimensional electron gas below the third electrode 23 decreases, and for example, virtually no two-dimensional electron gas is generated below the third electrode 23. This results in an OFF state where electrons do not substantially flow from the second electrode 22 through the first semiconductor layer 11 to the first electrode 21. In this example, a normally-on device is shown where the ON state is obtained when the third electrode 23 is 0V. However, the embodiment may also be a normally-off device where the OFF state is obtained when the third electrode 23 is 0V.

[0031] The effects of the embodiment will be explained with reference to the example. Figures 3(a) to 3(c) are schematic cross-sectional views illustrating a semiconductor device according to a reference example. Figures 3(a) to 3(c) illustrate the area around the first electrode 21 of the semiconductor device 190 according to a reference example. The semiconductor device 190 differs from the semiconductor device 100 according to the embodiment in that it does not have a conductive portion 50.

[0032] Figure 3(a) shows the state in the off state where a positive voltage is applied to the first electrode 21 relative to the second electrode 22. Figure 3(b) shows the state where the voltage applied to the first electrode 21 is greater than the voltage in Figure 3(a). Figure 3(c) shows the state where the voltage applied to the first electrode 21 is even greater than the voltage in Figure 3(b).

[0033] As shown in Figure 3(a), a two-dimensional electron gas G is formed in a portion between the first semiconductor layer 11 and the second semiconductor layer 12. The end De of the depletion layer is located on the third electrode 23 side of the two-dimensional electron gas G. As the voltage of the first electrode 21 increases, as shown in Figure 3(b), the region in which the two-dimensional electron gas G is formed narrows, and the end De of the depletion layer approaches the first electrode 21. In Figure 3(b), the end De is located near the bottom of the end 21fx of the first electrode extension 21f. At this time, an electric field E1 along the Z direction is generated between the second semiconductor layer 12 and the wiring extension 41f. As the voltage of the first electrode 21 increases further, as shown in Figure 3(c), the region in which the two-dimensional electron gas G is formed narrows even further, and the end De of the depletion layer approaches the first electrode portion 21e. In Figure 3(c), the end De is located near the bottom of the side surface of the first electrode portion 21e. At this time, an electric field E2 is generated between the second semiconductor layer 12 and the first electrode extension portion 21f, along the Z direction.

[0034] When the depletion layer reaches the vicinity of the first electrode 21, a strong longitudinal electric field is generated between the second semiconductor layer 12 and the extension portion 21f of the first electrode, and between the second semiconductor layer 12 and the wiring extension portion 41f.

[0035] Figures 4(a) and 4(b) are schematic cross-sectional views illustrating semiconductor devices. Figure 4(a) illustrates semiconductor device 190, and Figure 4(b) illustrates semiconductor device 100. As shown in Figure 4(a), electrons e are injected from the second semiconductor layer 12 into the insulating layer 30 and into the interface B between the second semiconductor layer 12 and the insulating layer 30 due to the longitudinal electric field explained in Figures 3(a) to 3(c). The injected electrons e are trapped in the insulating layer 30 and interface B. The trapped electrons e may affect the two-dimensional electron gas formed at the interface between the first semiconductor layer 11 and the second semiconductor layer 12, for example, in the ON state. For example, the electric field generated by the electrons e may decrease the electron density of the two-dimensional electron gas, potentially increasing the ON resistance.

[0036] In contrast, in this embodiment, a conductive portion 50 is provided on the second semiconductor layer 12, as described in Figure 1, with a length L1 longer than the length L2 of the first electrode extension portion 21f, and in contact with the first electrode 21. As shown in Figure 4(b), for example, electrons e that reach the conductive portion 50 located below the first electrode extension portion 21f from the second semiconductor layer 12 are discharged from the conductive portion 50 to the first electrode 21. The conductive portion 50 prevents electrons e from being trapped in the insulating layer 30 or interface B, thus suppressing an increase in on-resistance. According to this embodiment, for example, current collapse can be suppressed, and stable characteristics can be obtained.

[0037] As described with respect to Figure 1, for example, the length L1 of the conductive portion 50 may be longer than the length L3 of the wiring extension portion 41f. By forming the conductive portion 50 so widely, the trapping of electrons e in the insulating layer 30 or interface B can be further suppressed. However, in this embodiment, the length L3 may be longer than the length L1. When the length L3 is long, the electrical resistance of the wiring layer 41 can be suppressed.

[0038] Although not shown in the diagram, another wiring layer 41 may be laminated on top of the wiring layer 41. The length L3 of the wiring extension portion 41f of each wiring layer 41 may be longer than, for example, the length L2 of the first electrode extension portion 21f and shorter than the length L1 of the conductive portion 50.

[0039] Furthermore, as shown in Figure 1, the first electrode portion 21e is in contact with the upper surface 50s of a part of the conductive portion 50 and the upper surface 12u of the second semiconductor layer 12. In other words, the first electrode portion 21e is in contact with the upper surface of the conductive portion 50 and the upper surface of the second semiconductor layer 12. In this way, for example, the first electrode portion 21e is made to make more reliable contact with both the conductive portion 50 and the second semiconductor layer 12.

[0040] For example, as shown in Figure 4(b), the thickness T50 (length along the Z direction) of the conductive portion 50 is thinner than the thickness T21f of the first electrode extension portion 21f and thinner than the thickness T30a of the first insulating portion 30a. By making the conductive portion 50 relatively thin, the thickness of the first electrode 21 can be reduced, for example, and the increase in the resistance component in the Z direction is suppressed.

[0041] The conductive portion 50 may be provided around the first electrode 21. For example, as shown in Figure 1, in the X direction, the end 50x of the conductive portion 50 is between the end 41fx of the wiring extension portion 41f and the end 42fx of the wiring extension portion 42f. The length L4 along the X direction between the end 50x of the conductive portion 50 and the end 42fx of the wiring extension portion 42f is longer than the difference between length L1 and length L3, and longer than the difference between length L1 and length L2. For example, length L4 is longer than length L1.

[0042] Figures 5 to 8 are schematic plan views illustrating a semiconductor device according to a modified embodiment. Figures 5 to 8 show the planar arrangement of the peripheral portion of the first electrode 21 in semiconductor devices 101 to 104 according to a modified embodiment. Semiconductor devices 101 to 104 differ from semiconductor device 100 shown in Figure 2 in the planar shape of the conductive portion 50 and the first electrode 21.

[0043] In the semiconductor device 101 shown in Figure 5, a plurality of first electrodes 21 and a plurality of conductive parts 50 are provided. The plurality of first electrodes 21 and the plurality of conductive parts 50 are arranged in the Y direction. Each conductive part 50 is provided so as to be in contact with each first electrode 21. In other words, one conductive part 50 is in contact with one first electrode 21. In addition, one wiring layer 41 extends in the Y direction and is provided on the plurality of first electrodes 21. The wiring layer 41 is electrically connected to each first electrode 21.

[0044] In a plan view along the Z direction, the outer edge of the first electrode extension 21f may be provided so as to surround the first electrode portion 21e. The planar shape of the outer edge of the first electrode extension 21f may be, for example, rectangular. That is, the first electrode extension 21f of the first electrode 21 may extend from the first electrode portion 21e in all four directions (X direction and Y direction).

[0045] In a plan view along the Z direction, the outer edge of the conductive portion 50 may be provided so as to surround the first electrode 21, for example. The planar shape of the outer edge of the conductive portion 50 may be rectangular, for example. For example, the length L50 of the conductive portion 50 along the Y direction is longer than the length L21f of the first electrode extension portion 21f along the Y direction. The first electrode extension portion 21f has both ends (ends f1 and f2) in the Y direction. Ends f1 and f2 are positioned to overlap with the conductive portion 50 in the Z direction. For example, in a plan view along the Z direction, ends f1 and f2 are located between the ends (ends g1 and g2) of the conductive portion 50 in the Y direction. By forming the conductive portion 50 so that it is wider than the first electrode 21 in this way, the trapping of electrons e in the insulating layer 30 and the like can be further suppressed.

[0046] In the semiconductor device 102 shown in Figure 6, multiple first electrodes 21 are provided for one conductive portion 50. The multiple first electrodes 21 are arranged in the Y direction. One conductive portion 50 extends in the Y direction and is in contact with the multiple first electrodes 21.

[0047] In the semiconductor device 103 shown in Figure 7, the width W50 (length along the X direction) of the conductive portion 50 is narrower than the width of the conductive portion 50 in the semiconductor device 102 shown in Figure 6. In the semiconductor device 103, a portion f1a of the end f1 (side) of the first electrode 21 overlaps with the conductive portion 50 in the Z direction. On the other hand, another portion f1b of the end f1 does not overlap with the conductive portion 50 in the Z direction. Note that portion f1a is the part closer to the second electrode 22 than portion f1b. Similarly, in the semiconductor device 103, a portion f2a of the end f2 (side) of the first electrode 21 overlaps with the conductive portion 50 in the Z direction. On the other hand, another portion f2b of the end f2 does not overlap with the conductive portion 50 in the Z direction. Note that portion f2a is the part closer to the second electrode 22 than portion f2b.

[0048] In the examples shown in Figures 5 to 7, the width of the conductive portion 50 (length along the X direction) is, for example, constant. However, as in the semiconductor device 104 shown in Figure 8, the width of the conductive portion 50 may vary along the Y direction. For example, in the semiconductor device 104, the conductive portion 50 includes a plurality of wide portions 51 and a plurality of narrow portions 52 that are alternately arranged in the Y direction. The width W51 of the wide portions 51 is wider than the width W52 of the narrow portions 52. Each of the plurality of wide portions 51 is in direct contact with each of the plurality of first electrodes 21. The narrow portions 52 are separated from the first electrodes 21. In the example in Figure 8, the ends f1 (side) and f2 (side) of the first electrodes 21 do not overlap with the conductive portion 50 in the Z direction.

[0049] Figures 9(a) to 9(d) and 10(a) to 10(d) are schematic cross-sectional views illustrating the manufacturing process of a semiconductor device according to an embodiment. Figures 9(a) to 10(c) show only the area surrounding the region where the first electrode 21 is formed. Figure 10(d) shows the area surrounding the region where the first electrode 21, the second electrode 22, and the third electrode 23 are formed.

[0050] As shown in Figure 9(a), a second semiconductor layer 12 is provided on the first semiconductor layer 11. Then, a first insulating film 31 is formed on the second semiconductor layer 12 by, for example, LPCVD (Low-Pressure Chemical Vapor Deposition).

[0051] Subsequently, as shown in Figure 9(b), a portion of the first insulating film 31 is removed, for example, by reactive ion etching, to form an opening OP1. At the opening OP1, the upper surface 12u of the second semiconductor layer 12 is exposed.

[0052] Subsequently, as shown in Figure 9(c), a conductive film 50f is formed, for example, by sputtering. The conductive film 50f is provided on the first insulating film 31 and on the upper surface 12u of the second semiconductor layer 12.

[0053] Subsequently, as shown in Figure 9(d), for example, a portion of the conductive film 50f is removed from the first insulating film 31 and a portion of the upper surface 12u of the second semiconductor layer 12 by wet etching. This exposes the upper surface of the first insulating film 31 and the first region 12ua, which is a portion of the upper surface 12u, and the conductive portion 50 is formed.

[0054] Subsequently, as shown in Figure 10(a), a second insulating film 32 is formed on the first insulating film 31, on the second semiconductor layer 12 (the first region 12ua on the upper surface 12u), and on the conductive portion 50 by, for example, PECVD (Plasma-Enhanced Chemical Vapor Deposition). At this time, the second insulating film 32 covers, for example, the entire conductive portion 50 and the first region 12ua.

[0055] Subsequently, as shown in Figure 10(b), a first insulating portion 30a is formed on the first portion 50a of the conductive portion 50. That is, a portion of the second insulating film 32 is removed from the upper surface 12ub of a part of the second semiconductor layer 12 and the upper surface 50s of the second portion 50b of the conductive portion 50 by reactive ion etching, for example, to form an opening OP2 in the second insulating film 32. The upper surface 50s and the upper surface 12ub are exposed at the opening OP2. The upper surface 12ub is a part of the first region 12ua of the upper surface 12u.

[0056] Subsequently, as shown in Figure 10(c), the first electrode 21 is formed inside the opening OP2 and on the first insulating portion 30a. Specifically, for example, an electrode film that will become the first electrode 21 is formed on the second insulating film 32, the upper surface 50s, and the upper surface 12ub. The first electrode 21 is formed by removing a portion of the electrode film from a portion 32a of the second insulating film 32 by reactive ion etching or the like. Of the first electrode 21, the portion provided on the upper surface 50s and the upper surface 12ub inside the opening OP2 becomes the first electrode portion 21e. Of the first electrode 21, the portion provided on the first insulating portion 30a becomes the first electrode extension portion 21f.

[0057] As shown in Figure 10(d), the second electrode 22 is formed. The formation of the second electrode 22 may be performed simultaneously with the formation of the first electrode 21, for example. That is, when forming the opening OP2, an opening OP3 is formed in the first insulating film 31 and the second insulating film 32, depending on the position where the second electrode 22 is to be formed. The second semiconductor layer 12 is exposed at the opening OP3. Subsequently, the electrode film described above is also formed inside the opening OP3, and the second electrode 22 is formed by processing it simultaneously with the first electrode 21 by reactive ion etching or the like.

[0058] Furthermore, the third electrode 23 is formed by an appropriate method and timing. For example, the third electrode 23 may be formed by embedding it in the second insulating film 32 before forming the first electrode 21 and the second electrode 22. Alternatively, the third electrode 23 may be formed before forming the second insulating film 32, and then the second insulating film 32 may be laminated and polished.

[0059] In the embodiment, as explained with respect to Figure 9(d), for example, a portion of the conductive film 50f is processed by wet etching. By using wet etching, the impact (damage) on the second semiconductor layer 12 can be suppressed compared to when dry etching is used. For example, a decrease in the carrier density in the two-dimensional electron gas can be suppressed. As the etching solution for wet etching, for example, if the material of the conductive film 50f is TiN, a mixture of hydrochloric acid, hydrogen peroxide, and water can be used.

[0060] Furthermore, as explained with respect to Figure 10(c), for example, the second semiconductor layer 12 and the conductive portion 50 are exposed at the opening OP2, and the first electrode portion 21e is formed thereon. This allows for a more reliable connection between the conductive portion 50 and the first electrode portion 21e while forming an ohmic junction between the first electrode portion 21e and the second semiconductor layer 12.

[0061] As described above, the material of the first electrode 21 may be different from the material of the conductive portion 50. For example, a material that easily forms an ohmic junction with the second semiconductor layer 12 can be selected for the first electrode 21, and a material that is easy to process by wet etching can be selected for the conductive portion 50.

[0062] According to the embodiment, a semiconductor device capable of obtaining stable characteristics can be provided.

[0063] The embodiment may include the following configurations. (Composition 1) A first semiconductor layer containing a nitride semiconductor, A second semiconductor layer, comprising a nitride semiconductor, is provided on the first semiconductor layer, A first electrode comprising an electrode portion provided on the second semiconductor layer and in contact with the second semiconductor layer, and an electrode extension portion extending from the upper end of the electrode portion in a second direction perpendicular to a first direction toward the second semiconductor layer from the first semiconductor layer, A second electrode is provided on the aforementioned second semiconductor layer, and is separated from the aforementioned first electrode in the aforementioned second direction, A conductive portion that is in contact with the upper surface of the second semiconductor layer, located between the first electrode and the second electrode, and in contact with the first electrode, wherein the length along the second direction from the electrode portion to the end of the conductive portion on the second electrode side is longer than the length along the second direction from the electrode portion to the end of the electrode extension portion on the second electrode side, An insulating portion is provided on the conductive portion and is located between the conductive portion and the electrode extension portion, A third electrode is located above the second semiconductor layer via an insulating film and is positioned between the first electrode and the second electrode, A semiconductor device equipped with [the necessary components]. (Configuration 2) The semiconductor device according to configuration 1, wherein the electrode portion is in contact with the upper surface of a part of the conductive portion and the upper surface of the second semiconductor layer. (Composition 3) The first wiring layer is further provided on the first electrode, The first wiring layer includes a first wiring portion and a first wiring extension portion extending in the second direction from the upper end of the first wiring portion. The semiconductor device according to configuration 1 or 2, wherein the length along the second direction from the electrode portion to the end of the first wiring extension portion on the second electrode side is longer than the length along the second direction from the electrode portion to the end of the electrode extension portion on the second electrode side, and shorter than the length along the second direction from the electrode portion to the end of the conductive portion on the second electrode side. (Composition 4) The second wiring layer is further provided on the second electrode, The second wiring layer includes a second wiring portion and a second wiring extension portion extending from the upper end of the second wiring portion toward the first electrode side. A semiconductor device according to any one of configurations 1 to 3, wherein the length along the second direction between the end of the conductive portion on the second electrode side and the end of the second wiring extension portion on the first electrode side is longer than the length along the second direction from the electrode portion to the end of the conductive portion on the second electrode side. (Composition 5) The second wiring layer is further provided on the second electrode, The second wiring layer includes a second wiring portion and a second wiring extension portion extending from the upper end of the second wiring portion toward the first electrode side. A semiconductor device according to any one of configurations 1 to 4, wherein the length along the second direction between the end of the conductive portion on the second electrode side and the end of the second wiring extension portion on the first electrode side is longer than the difference between the length along the second direction from the electrode portion to the end of the conductive portion on the second electrode side and the length along the second direction from the electrode portion to the end of the electrode extension portion on the second electrode side. (Composition 6) The second wiring layer is further provided on the second electrode, The second wiring layer includes a second wiring portion and a second wiring extension portion extending from the upper end of the second wiring portion toward the first electrode side. The semiconductor device according to configuration 3, wherein the length along the second direction between the end of the conductive portion on the second electrode side and the end of the second wiring extension portion on the first electrode side is longer than the difference between the length along the second direction from the electrode portion to the end of the conductive portion on the second electrode side and the length along the second direction from the electrode portion to the end of the first wiring extension portion on the second electrode side. (Composition 7) Multiple first electrodes are provided, Multiple conductive parts are provided, A semiconductor device according to any one of configurations 1 to 6, wherein each of the plurality of conductive parts is in contact with each of the plurality of first electrodes. (Composition 8) Multiple first electrodes are provided, A semiconductor device according to any one of configurations 1 to 6, wherein one of the conductive parts is in contact with a plurality of first electrodes. (Composition 9) The length of the conductive portion in the third direction perpendicular to the first direction and perpendicular to the second direction is longer than the length of the electrode extension in the third direction. The semiconductor device according to any one of configurations 1 to 8, wherein the end of the electrode extension in the third direction is located at a position that overlaps with the conductive portion in the first direction. (Composition 10) The semiconductor device according to any one of configurations 1 to 9, wherein the thickness of the conductive portion is thinner than the thickness of the electrode extension portion. (Composition 11) The semiconductor device according to any one of configurations 1 to 10, wherein the material of the conductive part is different from the material of the first electrode. (Composition 12) A first insulating film is provided on the second semiconductor layer and includes the insulating film portion, A second insulating film is provided on the first insulating film, with a portion of it provided on the conductive portion, A third insulating film is provided on the second insulating film, with a portion of it provided on the electrode extension portion, A semiconductor device according to any one of configurations 1 to 11, further comprising the above. (Composition 13) A step of forming a conductive portion on a part of a second semiconductor layer, which is provided on a first semiconductor layer containing a nitride semiconductor and also contains a nitride semiconductor, A step of forming an insulating portion on the first portion of the conductive portion, A step of forming a first electrode, which includes an electrode portion located on the second semiconductor layer and in contact with the second semiconductor layer and the conductive portion, and an electrode extension portion located on the insulating portion and extending from the upper end of the electrode portion in a second direction perpendicular to the first direction from the first semiconductor layer to the second semiconductor layer, A step of forming a second electrode, which is located away from the first electrode and the conductive portion in the second direction, wherein the length along the second direction from the electrode portion to the end of the conductive portion on the second electrode side is longer than the length along the second direction from the electrode portion to the end of the electrode extension on the second electrode side; A step of forming a third electrode located above the second semiconductor layer via an insulating film and positioned between the first electrode and the second electrode, A method for manufacturing a semiconductor device equipped with [the specified features]. (Composition 14) The method for manufacturing a semiconductor device according to configuration 13, wherein the step of forming the conductive portion includes forming a conductive film on the second semiconductor layer and removing a portion of the conductive film by wet etching. (Composition 15) The step of forming the insulating portion includes forming an insulating film that is provided on the second semiconductor layer and the conductive portion and covers the conductive portion, The method for manufacturing a semiconductor device according to configuration 13 or 14, wherein the step of forming the first electrode includes forming a part of the electrode portion within the opening.

[0064] In this specification, "perpendicular" does not mean strictly perpendicular, but includes variations in the manufacturing process, for example; it is sufficient if it is substantially perpendicular. In this specification, "electrically connected" includes not only cases where the connection is made by direct contact, but also cases where the connection is made via other conductive members or the like. The phrase "placed on top of" one element may include not only cases where the two elements are touching (or continuous) with each other, but also cases where another element is placed between the two elements. For example, the phrase "placed on top of" one element may include cases where one element is located above another element, regardless of whether the two elements are touching each other or not.

[0065] Although several embodiments of the present invention have been illustrated above, these embodiments are presented as examples only and are not intended to limit the scope of the invention. These novel embodiments can be implemented in various 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. Furthermore, the embodiments described above can be implemented in combination with each other. [Explanation of Symbols]

[0066] 11: First semiconductor layer 12: Second semiconductor layer 12u:Top surface 12ua: 1st area 12ub:Top surface 21: 1st electrode 21e: 1st electrode part 21f: First electrode extension part 21fx: end 22:Second electrode 22e: Second electrode part 22f: Second electrode extension part 22fx: end 23: Third electrode 30: Insulating layer 30a: First insulating section 30b: Second insulating section 31: First insulating film 31a: Insulating film portion 32: Second insulating film 32a: some 33: Third insulating film 35: Insulating layer 41: Wiring layer 41e: Wiring section 41f: Wiring extension section 41fx: end 42: Wiring layer 42e: Wiring section 42f: Wiring extension section 42fx: end 50: Conductive part 50a: 1st part 50b:Second part 50f: Conductive film 50s:Top surface 50x: end 51: Wide section 52: Narrow part 53: Third electrode 61: Conductive material 62: Conductive material 100-104, 190: Semiconductor devices B: Interface De: Edge of the depletion layer E1, E2: Electric field G: Two-dimensional electron gas L1~L4, L21f, L50: Length OP1~OP3: Opening T21f, T30a, T50: Thickness W50, W51, W52: Width f1, f2: Edge f1a, f1b, f2a, f2b: Part of the end g1, g2: End

Claims

1. A first semiconductor layer containing a nitride semiconductor, A second semiconductor layer, comprising a nitride semiconductor, is provided on the first semiconductor layer, A first electrode comprising an electrode portion provided on the second semiconductor layer and in contact with the second semiconductor layer, and an electrode extension portion extending from the upper end of the electrode portion in a second direction perpendicular to the first direction toward the second semiconductor layer from the first semiconductor layer, A second electrode is provided on the second semiconductor layer, and is separated from the first electrode in the second direction, A conductive portion that is in contact with the upper surface of the second semiconductor layer, located between the first electrode and the second electrode, and in contact with the first electrode, wherein the length along the second direction from the electrode portion to the end of the conductive portion on the second electrode side is longer than the length along the second direction from the electrode portion to the end of the electrode extension portion on the second electrode side, An insulating portion is provided on the conductive portion and is located between the conductive portion and the electrode extension portion, A third electrode is located above the second semiconductor layer via an insulating film and is positioned between the first electrode and the second electrode, Equipped with, The electrode portion is a semiconductor device that is in contact with the upper surface of a part of the conductive portion and the upper surface of the second semiconductor layer.

2. The first wiring layer is further provided on the first electrode, The first wiring layer includes a first wiring portion and a first wiring extension portion extending in the second direction from the upper end of the first wiring portion. The semiconductor device according to claim 1, wherein the length along the second direction from the electrode portion to the end of the first wiring extension portion on the second electrode side is longer than the length along the second direction from the electrode portion to the end of the electrode extension portion on the second electrode side, and shorter than the length along the second direction from the electrode portion to the end of the conductive portion on the second electrode side.

3. The second wiring layer is further provided on the second electrode, The second wiring layer includes a second wiring portion and a second wiring extension portion extending from the upper end of the second wiring portion toward the first electrode side. The semiconductor device according to claim 1, wherein the length along the second direction between the end of the conductive portion on the second electrode side and the end of the second wiring extension portion on the first electrode side is longer than the length along the second direction from the electrode portion to the end of the conductive portion on the second electrode side.

4. The second wiring layer is further provided on the second electrode, The second wiring layer includes a second wiring portion and a second wiring extension portion extending from the upper end of the second wiring portion toward the first electrode side. The semiconductor device according to claim 1, wherein the length in the second direction between the end of the conductive portion on the second electrode side and the end of the second wiring extension portion on the first electrode side is longer than the difference between the length in the second direction from the electrode portion to the end of the conductive portion on the second electrode side and the length in the second direction from the electrode portion to the end of the electrode extension portion on the second electrode side.

5. The second wiring layer is further provided on the second electrode, The second wiring layer includes a second wiring portion and a second wiring extension portion extending from the upper end of the second wiring portion toward the first electrode side. The semiconductor device according to claim 2, wherein the length in the second direction between the end of the conductive portion on the second electrode side and the end of the second wiring extension portion on the first electrode side is longer than the difference between the length in the second direction from the electrode portion to the end of the conductive portion on the second electrode side and the length in the second direction from the electrode portion to the end of the first wiring extension portion on the second electrode side.

6. Multiple first electrodes are provided, Multiple conductive parts are provided, The semiconductor device according to claim 1, wherein each of the plurality of conductive parts is in contact with each of the plurality of first electrodes.

7. Multiple first electrodes are provided, The semiconductor device according to claim 1, wherein one of the conductive parts is in contact with a plurality of the first electrodes.

8. The length of the conductive portion in the third direction perpendicular to the first direction and perpendicular to the second direction is longer than the length of the electrode extension in the third direction. The semiconductor device according to claim 1, wherein the end of the electrode extension in the third direction is located at a position that overlaps with the conductive portion in the first direction.

9. The semiconductor device according to claim 1, wherein the thickness of the conductive portion is thinner than the thickness of the electrode extension portion.

10. The semiconductor device according to claim 1, wherein the material of the conductive part is different from the material of the first electrode.

11. A first insulating film is provided on the second semiconductor layer and includes the insulating film portion, A second insulating film is provided on the first insulating film, with a portion of it provided on the conductive portion, A third insulating film is provided on the second insulating film, with a portion of it provided on the electrode extension portion, The semiconductor device according to claim 1, further comprising the above.

12. A step of forming a conductive portion on a part of a second semiconductor layer, which is provided on a first semiconductor layer containing a nitride semiconductor and also contains a nitride semiconductor, A step of forming an insulating portion on the first portion of the conductive portion, A step of forming a first electrode, which includes an electrode portion located on the second semiconductor layer and in contact with the upper surface of the second semiconductor layer and the upper surface of a part of the conductive portion, and an electrode extension portion located on the insulating portion and extending from the upper end of the electrode portion in a second direction perpendicular to the first direction toward the second semiconductor layer, A step of forming a second electrode, which is located away from the first electrode and the conductive portion in the second direction, wherein the length along the second direction from the electrode portion to the end of the conductive portion on the second electrode side is longer than the length along the second direction from the electrode portion to the end of the electrode extension on the second electrode side, A step of forming a third electrode located above the second semiconductor layer via an insulating film and positioned between the first electrode and the second electrode, A method for manufacturing a semiconductor device equipped with [the specified features].

13. The method for manufacturing a semiconductor device according to claim 12, wherein the step of forming the conductive portion includes forming a conductive film on the second semiconductor layer and removing a portion of the conductive film by wet etching.

14. The step of forming the insulating portion includes forming an insulating film on the second semiconductor layer and the conductive portion and covering the conductive portion, and removing a part of the insulating film to form an opening in the insulating film. The method for manufacturing a semiconductor device according to claim 12 or 13, wherein the step of forming the first electrode includes forming a part of the electrode portion within the opening.

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