Semiconductor devices and high-frequency modules

Abstract

The semiconductor device according to this disclosure comprises a GaN layer having an upper surface and a back surface opposite to the upper surface, and provided with a BAW propagation section configured to propagate BAW of a predetermined frequency in the direction from the upper surface to the back surface; a first via hole provided around the BAW propagation section of the GaN layer; an upper ground electrode provided on at least the BAW propagation section of the GaN layer; and a lower ground electrode provided on at least the BAW propagation section of the GaN layer.

Description

[Technical Field]

[0001] This disclosure relates to semiconductor devices and high-frequency modules. [Background technology]

[0002] Patent Document 1 discloses a power amplifier aimed at reducing the impedance of the connection circuit as seen from the terminal of a unit transistor at the difference frequency for all of the multiple transistors arranged, thereby preventing deterioration of distortion characteristics. [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] International Publication No. 2020 / 202532 [Overview of the Initiative] [Problems that the invention aims to solve]

[0004] In amplifiers for satellite communications, multi-carrier operation is required to increase transmission capacity. Broadening the detuning frequency Δf is crucial for multi-carrier operation. As shown in Patent Document 1, reducing the impedance at Δf as seen from the transistor is effective in reducing distortion at Δf. Generally, the impedance at Δf of approximately 1 to 400 MHz can be reduced by mounting chip capacitors or the like outside the semiconductor chip or package. However, in the region Δf > 400 MHz, the influence of the wire length connected to the semiconductor chip is significant. Therefore, impedance reduction, i.e., wide detuning, in the region Δf > 400 MHz has been difficult.

[0005] This disclosure aims to provide a semiconductor device and a high-frequency module that enable broadband detuning of the frequency range. [Means for solving the problem]

[0006] FirstThe disclosed semiconductor device comprises a GaN layer having an upper surface and a back surface opposite to the upper surface, and provided with a BAW propagation section configured to propagate BAW of a predetermined frequency in the direction from the upper surface to the back surface; a first via hole provided around the BAW propagation section in the GaN layer; an upper ground electrode provided on at least the BAW propagation section in the GaN layer; and a lower ground electrode provided on at least the BAW propagation section in the GaN layer. There is no metal layer on the inner wall of the first via hole. . The semiconductor device according to the second disclosure comprises a GaN layer having an upper surface and a back surface opposite to the upper surface, and provided with a BAW propagation section configured to propagate BAW of a predetermined frequency in the direction from the upper surface to the back surface; a first via hole provided around the BAW propagation section of the GaN layer; an upper ground electrode provided on at least the BAW propagation section of the GaN layer; and a lower ground electrode provided on at least the BAW propagation section of the GaN layer, wherein the first via hole is provided so as to surround the BAW propagation section. The semiconductor device according to the third disclosure comprises a GaN layer having an upper surface and a back surface opposite to the upper surface, and provided with a BAW propagation section configured to propagate BAW of a predetermined frequency in the direction from the upper surface to the back surface; a first via hole provided around the BAW propagation section of the GaN layer; an upper ground electrode provided on at least the BAW propagation section of the GaN layer; and a lower ground electrode provided on at least the BAW propagation section of the GaN layer, wherein the thickness of the GaN layer is 25 μm or more. The semiconductor device according to the fourth disclosure comprises a GaN layer having an upper surface and a back surface opposite to the upper surface, and provided with a BAW propagation section configured to propagate BAW of a predetermined frequency in the direction from the upper surface to the back surface; a first via hole provided around the BAW propagation section of the GaN layer; an upper ground electrode provided on at least the BAW propagation section of the GaN layer; a lower ground electrode provided on at least the BAW propagation section of the GaN layer; and a quarter-wavelength stub provided on the GaN layer, wherein the upper ground electrode is connected to the quarter-wavelength stub.

[0007] The semiconductor device according to this disclosure comprises a GaN layer having an upper surface and a back surface opposite to the upper surface, a first electrode inserted into the GaN layer from the upper surface of the GaN layer, and a second electrode inserted into the GaN layer from either the upper surface or the back surface of the GaN layer and provided at a position horizontally offset from the first electrode, wherein the GaN layer is configured to propagate BAW of a predetermined frequency in the horizontal direction and in the direction from the first electrode to the second electrode. [Effects of the Invention]

[0008] In the semiconductor device according to this disclosure, the impedance at Δf can be reduced by making the portion of the GaN layer through which the BAW propagates resonate at a desired Δf. Therefore, it becomes possible to broaden the detuning frequency bandwidth. [Brief explanation of the drawing]

[0009] [Figure 1] This is a cross-sectional view of the semiconductor device according to Embodiment 1. [Figure 2] This is a plan view of the semiconductor device according to Embodiment 1. [Figure 3] This is a cross-sectional view of a semiconductor device relating to a comparative example. [Figure 4] This diagram illustrates the propagation of BAW in a semiconductor device according to Embodiment 1. [Figure 5]Cross-sectional view of the semiconductor device according to Embodiment 2. [Figure 6] Diagram showing the equivalent circuit of the BAW propagation section according to Embodiment 2. [Figure 7] Cross-sectional view of the semiconductor device according to Embodiment 3. [Figure 8] Planar view of the semiconductor device according to Embodiment 3. [Figure 9] Cross-sectional view of the semiconductor device according to Embodiment 3. [Figure 10] Diagram showing the crystal structure of GaN. [Figure 11] Cross-sectional view of the semiconductor device according to Embodiment 4. [Figure 12] Planar view of the semiconductor device according to Embodiment 4. [Figure 13] Diagram for explaining the configuration of the semiconductor device according to Embodiment 5. [Figure 14] Diagram showing the impedance of the semiconductor device according to Embodiment 5. [Figure 15] Diagram showing the insertion loss of the semiconductor device according to Embodiment 5. [Figure 16] Cross-sectional view showing a semiconductor device combining the 1 / 4 wavelength stub according to Embodiment 5 and the configuration of Embodiment 1. [Figure 17] Cross-sectional view showing a semiconductor device combining the 1 / 4 wavelength stub according to Embodiment 5 and the configuration of Embodiment 2. [Figure 18] Cross-sectional view showing a semiconductor device combining the 1 / 4 wavelength stub according to Embodiment 5 and the configuration of Embodiment 3. [Figure 19] Cross-sectional view showing a semiconductor device combining the 1 / 4 wavelength stub according to Embodiment 5 and the configuration of Embodiment 4. [Figure 20] Diagram for explaining the configuration of the high-frequency module according to Embodiment 6.

Embodiments for Carrying Out the Invention

[0010] The semiconductor devices and high-frequency modules according to each embodiment will be described with reference to the drawings. The same or corresponding components are denoted by the same reference numerals, and repetition of the description may be omitted.

[0011] Embodiment 1. Figure 1 is a cross-sectional view of the semiconductor device 100 according to Embodiment 1. Figure 2 is a plan view of the semiconductor device 100 according to Embodiment 1. The semiconductor device 100 comprises a GaN layer 10 having an upper surface and a back surface opposite to the upper surface. The GaN layer 10 is, for example, an epitaxial growth layer on a SiC substrate 30. The thickness of the GaN layer 10 is, for example, 100 nm to 1 μm. The semiconductor device 100 is, for example, a GaN MMIC (Monolithic Microwave Integrated Circuit) using a SiC, Si, or GaN substrate. The semiconductor device 100 may also be a GaN IMFET (Impedance Matched Field Effect Transistor) chip. In this embodiment, the substrate is SiC, but Si, sapphire, diamond, or AlN may also be used.

[0012] As will be described later, the GaN layer 10 is provided with a BAW propagation section 15 configured to propagate a BAW (Bulk Acoustic Wave) of a predetermined frequency in the direction A1 from the top surface to the back surface.

[0013] Via holes 12 are provided around the BAW propagation portion 15 of the GaN layer 10. The via holes 12 are provided so as to surround the BAW propagation portion 15. The inner surface of the via holes 12 may be covered with a metal layer. An upper ground electrode 21 is provided above the BAW propagation portion 15 of the GaN layer 10. In addition, a lower ground electrode 22 is provided below the BAW propagation portion 15 of the GaN layer 10.

[0014] A SiC substrate 30 is provided on the back surface of the GaN layer 10. A back metal 26 is provided on the SiC substrate 30 opposite to the GaN layer 10. Via holes 32 are provided in the SiC substrate 30. The base electrode 22 and the back metal 26 are electrically connected by a metal 25 covering the inner wall of the via hole 32. The back metal 26 is connected to, for example, a GND metal 27 and grounded. Note that, depending on the application, the back metal 26 does not need to be grounded.

[0015] A transistor is formed on the GaN layer 10. In reality, an epitaxial layer necessary for the transistor is formed on top of the GaN layer 10, but since the thickness of these layers is sufficiently thinner than the thickness of the GaN layer 10, they are omitted in Figure 1. The source electrode 41, drain electrode 42, and gate electrode 43 of the transistor are provided on top of the GaN layer 10. The drain electrode 42 is electrically connected to the ground electrode 21 via wiring 23 and an air bridge 24. The air bridge 24 is provided so as to span the via hole 12.

[0016] Next, the effects of this embodiment will be described. GaN has piezoelectric properties. Therefore, the RF (Radio Frequency) signal propagates as BAW from the upper ground electrode 21 to the lower ground electrode 22. After the BAW reaches the lower electrode 22, it is connected to GND. This reduces the impedance at the frequency in which the BAW propagates. In this embodiment, the impedance at Δf can be reduced by making the BAW propagation portion 15 of the GaN layer 10 sized to resonate at a desired Δf. Therefore, it becomes possible to broaden the detuning frequency band.

[0017] In particular, in this embodiment, the impedance can be reduced by providing a BAW propagation section 15 within the semiconductor chip. Therefore, there is no need to use wires, and the impedance at Δf > 400 MHz can be reduced by setting the BAW propagation section 15 to a size that resonates at, for example, 400 MHz or higher. Thus, wide detuning can be performed stably without being affected by wire variations.

[0018] For example, the resonant frequency of the BAW propagation section 15 can be adjusted by adjusting the area of ​​the upper ground electrode 21 or the lower ground electrode 22. In other words, the area of ​​the portion sandwiched between the upper ground electrode 21 and the lower electrode 22 in a plan view is adjusted.

[0019] Figure 3 is a cross-sectional view of a comparative example semiconductor device. In the comparative example semiconductor device, via holes 12 are not provided. In this case, there is a risk of BAW leakage as shown by arrow A2. Also, as shown by arrow A3, there is a risk of BAW interference between adjacent electrodes.

[0020] Figure 4 illustrates the propagation of BAW in the semiconductor device 100 according to Embodiment 1. In this embodiment, via holes 12 provided around the BAW propagation section 15 can block BAW leakage to the outside of the upper ground electrode 21 and the lower ground electrode 22. Therefore, the propagation loss of BAW can be reduced. In addition, interference of BAW between adjacent electrodes can be avoided. Therefore, good BAW characteristics can be obtained.

[0021] Furthermore, the base electrode 22 can be formed using a back-side process. Therefore, unlike conventional FBARs (Film Bulk Acoustic Resonators), GaN regrowth, i.e., epitaxial growth after electrode formation, is unnecessary. Consequently, processing costs can be reduced. In this embodiment, the GaN epitaxial layer of a GaN transistor is used as the BAW propagation section 15. This allows for the formation of a structure on the MMIC chip to reduce impedance. Furthermore, chip components such as capacitors can be reduced. Consequently, the entire module can be miniaturized.

[0022] In Figure 2, via holes 12 are provided on all four sides of the upper ground electrode 21 or the BAW propagation section 15 in a plan view. However, the via holes 12 only need to be provided around at least a portion of the BAW propagation section 15. For example, via holes 12 may be provided on both sides of the BAW propagation section 15. Via holes 12 may also be provided around the entire circumference of the upper ground electrode 21, including the corners of the upper ground electrode 21, in a plan view.

[0023] The modifications described above can be appropriately applied to the semiconductor device and high-frequency module according to the following embodiments. Since the semiconductor device and high-frequency module according to the following embodiments have many similarities with Embodiment 1, the explanation will focus on the differences from Embodiment 1.

[0024] Embodiment 2. Figure 5 is a cross-sectional view of a semiconductor device 200 according to Embodiment 2. In this embodiment, a GaN layer 210, which is a GaN substrate, is used instead of the GaN layer 10, which is an epitaxial growth layer. The thickness of the GaN layer 10 in Embodiment 1 is, for example, 500 nm, while the GaN layer 210 in this embodiment is, for example, 100 μm. Also, the semiconductor device 200 is not provided with a SiC substrate 30. The base electrode 22 is provided on the back surface of the GaN layer 210. There is no metal layer on the inner wall of the via hole 12. The base electrode 22 is connected to the GND metal 27 without going through the semiconductor substrate. The upper ground electrode 21 is provided so as to block the via hole 12. As a measure to prevent short circuits between the upper ground electrode 21 and the base electrode 22 by die bond materials such as solder during chip mounting, a semiconductor layer 218 may be left on the upper side of the via hole 12. The semiconductor layer 218 may be the GaN layer 210 below the upper ground electrode 21, or it may be an epitaxial layer that contributes to the transistor structure. The other components are the same as those in Embodiment 1.

[0025] Figure 6 shows the equivalent circuit of the BAW propagation section according to Embodiment 2. C0 is the capacitance, which can be calculated using the following formula.

[0026]

number

[0027] ε0 is the permittivity of vacuum, ε r is the relative permittivity of GaN, S is the electrode area, and d is the thickness of the GaN layer. C m This is the operating capacitance, which can be calculated using the following formula.

[0028]

number

[0029] t is the thickness of the BAW propagation section 15 and is expressed by the following formula.

[0030]

number

[0031] f res ν is the resonant frequency. ν is the speed of sound and is expressed by the following equation.

[0032]

number

[0033] E is the elastic modulus of GaN, and ρ is the density of GaN. L m This is the operating inductance, and can be calculated using the following formula.

[0034]

number

[0035] Q m This is the mechanical quality factor and can be calculated using the following formula.

[0036]

number

[0037] Δf is the bandwidth. R m This is the operating resistance, and can be calculated using the following formula.

[0038]

number

[0039] The substrate is thicker compared to the epitaxial growth layer. The thickness of the GaN layer is inversely proportional to the capacitance C0. Therefore, in this embodiment, the capacitance C0 can be lowered. This allows the semiconductor device 200 to be applied to higher frequencies. In addition, in this embodiment, the capacitance ratio C0 / C, which affects stability, is also important. m This reduces the noise. This allows the anti-resonant frequency to be moved away from the desired resonant frequency. Therefore, it becomes easier to design a stable amplifier. The thickness of the GaN layer 210 in this embodiment is, for example, 25 μm or more. The thickness of the GaN layer 210 may be 25 μm to 300 μm.

[0040] In this embodiment, via holes 12 are formed by etching from the back surface of the GaN layer 210. The covering portion 228 that covers the via holes 12 of the upper ground electrode 21 functions as a support metal during via hole processing. Of the upper ground electrode 21, the portion enclosed by the dashed frame directly above the BAW propagation section 15 contributes to BAW propagation. In Embodiment 1, the via holes 12 can be formed by etching from the upper surface of the GaN layer 10. Therefore, a support metal is not required in Embodiment 1.

[0041] Embodiment 3. Figures 7 and 9 are cross-sectional views of the semiconductor device 300 according to Embodiment 3. Figure 8 is a plan view of the semiconductor device 300 according to Embodiment 3. Figure 7 is a cross-sectional view obtained by cutting Figure 8 along the line A-A', and Figure 9 is a cross-sectional view obtained by cutting Figure 8 along the line B-B'. In this embodiment, electrodes 321 and 322 are inserted into the GaN layer 210 from the upper surface of the GaN layer 210. Electrode 322 is provided at a position horizontally offset from electrode 321. The GaN layer 210 is configured to propagate BAW at a predetermined frequency in the horizontal direction and in the direction A4 from electrode 321 to electrode 322. In other words, in this embodiment, the portion of the GaN layer 210 sandwiched between electrodes 321 and 322 becomes the BAW propagation section 15.

[0042] A via hole 314 is provided in the GaN layer 210. The electrode 322 is electrically connected to the back metal 326 via the wiring 351, the receiving metal 352 used during via hole 314 processing, and the metal 353 covering the inner wall of the via hole 314. The back metal 326 is connected to the GND metal 27. In this embodiment, the electrode 321 is also electrically connected to the electrode of a transistor (not shown).

[0043] In this embodiment as well, by making the BAW propagation portion 15 of the GaN layer 210 resonate at a desired Δf, the impedance at Δf can be reduced. Therefore, it becomes possible to broaden the detuning frequency band. Also, similar to embodiments 1 and 2, the impedance can be reduced at, for example, Δf > 400 MHz without being affected by the wire, and stable wide detuning can be achieved.

[0044] Via holes 312 are provided around the portion of the GaN layer 210 that is sandwiched between electrodes 321 and 322 in a plan view. The via holes 312 are formed to the same depth as electrodes 321, 322 and the BAW propagation section 15, for example. The via holes 312 are provided adjacent to the side of the BAW propagation section 15 where electrodes 321 and 322 are not provided, for example. Furthermore, via holes 313 are provided directly below the portion of the GaN layer 210 that is sandwiched between electrodes 321 and 322 in a plan view. This suppresses BAW leakage and interference.

[0045] Furthermore, a protective film 360 is provided on the upper surface of the GaN layer 210, specifically in the portion sandwiched between electrodes 321 and 322 in a plan view. Wiring, for example, is provided on top of the protective film 360. As shown in Figure 9, it is advisable to leave a portion of the GaN layer on the via holes 312 to maintain the structure, so as not to affect the BAW. In Figure 8, the GaN layer on top of the via holes 312 is omitted. In this embodiment, wiring 362 such as bias circuits can be placed on the protective film 360. Therefore, the chip area can be reduced.

[0046] Figure 10 shows the crystal structure of GaN. The piezoelectric properties that affect the BAW characteristics depend on the crystal axis. Generally, GaN substrates or GaN epitaxial transistors commonly used in GaN HEMTs (High Electron Mobility Transistors) and GaN HBTs (Heterojunction Bipolar Transistors) are grown in the c-axis direction. That is, the thickness direction of the substrate is the c-axis direction. The BAW characteristics depend on the crystal axis and structure. If the BAW propagation direction is good in the a-axis or m-axis direction, good BAW characteristics can be obtained in this embodiment.

[0047] Furthermore, when adjusting the resonant frequency of the BAW propagation section 15, in embodiments 1 and 2, the thickness of the BAW propagation section 15 in the BAW propagation direction A1 cannot be freely changed because it depends on the transistor structure or substrate thickness. On the other hand, in this embodiment, the thickness of the GaN layer 210 in the BAW propagation direction A4 can be freely designed. In this embodiment as well, the resonant frequency of the BAW propagation section 15 may also be adjusted by the area of ​​the portion sandwiched between electrodes 321 and 322 when viewed from the BAW propagation direction A4.

[0048] The via holes 312 and 313 around the BAW propagation section 15 do not need to be provided. Also, the location of the via hole 312 does not need to be anywhere other than around the BAW propagation section 15. The wiring 362 on the protective film 360 does not need to be provided. Also, components other than the wiring 362 may be provided on the protective film 360. Furthermore, when the semiconductor device 300 is used as a filter, the electrode 322 does not need to be connected to GND.

[0049] Embodiment 4. Figure 11 is a cross-sectional view of the semiconductor device 400 according to Embodiment 4. Figure 12 is a plan view of the semiconductor device 400 according to Embodiment 4. Figure 11 is a cross-sectional view obtained by cutting Figure 12 along the line A-A'. Note that the cross-section obtained by cutting Figure 12 along the line B-B' is the same as the cross-section shown in Figure 9. This embodiment differs from Embodiment 3 in that the electrode 422 is inserted into the GaN layer 210 from the back surface of the GaN layer 210. The electrode 422 is provided at a position shifted horizontally from the electrode 321. The GaN layer 210 is configured to propagate BAW of a predetermined frequency in the horizontal direction and in the direction A4 from the electrode 321 to the electrode 422.

[0050] In this embodiment, in addition to via holes 312 and 313, a via hole 412 is provided in the BAW propagation direction A4, on the opposite side of electrode 422 from electrode 321 and adjacent to electrode 422. In this embodiment, the portion of the GaN layer 210 sandwiched between electrode 321 and via holes 312 and 412 becomes the BAW propagation section 15. The via holes 312 and 412 are formed to the same depth as, for example, electrode 321 and the BAW propagation section 15. The other configurations are the same as those in Embodiment 3.

[0051] In this embodiment, the electrode 422 can be directly connected to the GND metal 27. Therefore, a new via hole is not required to propagate the BAW to GND. Consequently, the semiconductor device 400 can be miniaturized.

[0052] Embodiment 5. Figure 13 is a diagram illustrating the configuration of the semiconductor device 500 according to Embodiment 5. In this embodiment, the structure described in Embodiments 1 to 4 is connected to the end of a quarter-wavelength stub 570, which is approximately one-quarter wavelength of the carrier frequency, i.e., the fundamental wave. In this embodiment, the BAW propagation section 15 is sized to resonate at the second harmonic of the carrier frequency. At this time, a short circuit occurs at both Δf and the carrier frequency, and the BAW propagates. In other words, Δf is shorted to GND, the fundamental wave is open due to the quarter-wavelength stub 570, and the second harmonic is shorted to GND.

[0053] FIG. 14 is a diagram showing the impedance of the semiconductor device 500 according to Embodiment 5. FIG. 14 shows an example of impedance characteristics in a 27.5 - 31 GHz band MMIC. As shown in m3 of FIG. 14, according to this embodiment, it is possible to short-circuit the Δf = 1000 MHz band, which was difficult in the past. Further, as shown in m2 of FIG. 14, according to this embodiment, it is also possible to short-circuit the second harmonic of the 58 GHz band, which is the cause of the deterioration of the distortion level. Also, the impedance in the carrier frequency band of 27.5 - 31 GHz is sufficiently high. Thus, it is possible to simultaneously realize the two functions of wide tuning and reduction of the distortion level. Further, since two functions can be realized with one circuit, the semiconductor device 500 can be miniaturized.

[0054] Here, consider a comparative example using a short stub using a conventional MIM (Metal-Insulator-Metal) capacitor instead of the BAW propagation section 15 in Embodiments 1 to 4. In such a comparative example, when the carrier frequency is high, such as in the millimeter wave band, resonance is likely to occur around the carrier frequency due to parasitic components such as MIM or via holes. For this reason, the RF characteristics may be significantly degraded.

[0055] FIG. 15 is a diagram showing the through loss of the semiconductor device 500 according to Embodiment 5. The broken line S0 shows the through characteristics of the short stub according to the comparative example using MIM. In the comparative example, it can be seen that there is a dip near 27.5 - 31 GHz, which is the used band, and the through loss becomes large near the used band. The solid line S1 shows the through loss of the short stub according to this embodiment. In this embodiment, it can be seen that no dip occurs near the used band.

[0056] Note that the dip of Δf depends on the sizes of the BAW propagation section 15 and MIM. In the example of FIG. 15, the size of MIM is 746×428 μm 2 while the size of the BAW propagation section 15 is 200×200 μm 2Therefore, this embodiment also contributes to miniaturization. This is because the relative permittivity of GaN is higher than that of the MIM film normally used.

[0057] Figure 16 is a cross-sectional view showing a semiconductor device 100a combining the quarter-wavelength stub 570 according to Embodiment 5 and the configuration of Embodiment 1. Figure 17 is a cross-sectional view showing a semiconductor device 200a combining the quarter-wavelength stub 570 according to Embodiment 5 and the configuration of Embodiment 2. The quarter-wavelength stub 570 with a carrier frequency is provided on the GaN layers 10 and 210. The upper ground electrode 21 is connected to the quarter-wavelength stub 570.

[0058] Figure 18 is a cross-sectional view showing a semiconductor device 300a combining the quarter-wavelength stub 570 according to Embodiment 5 and the configuration of Embodiment 3. Figure 19 is a cross-sectional view showing a semiconductor device 400a combining the quarter-wavelength stub 570 according to Embodiment 5 and the configuration of Embodiment 4. The electrode 321 is connected to the quarter-wavelength stub 570.

[0059] In Figures 16-19, the end of the quarter-wavelength stub 570 opposite to the upper ground electrode 21 or electrode 321 is connected, for example, to the electrodes of a transistor or a matching circuit.

[0060] Embodiment 6. Figure 20 is a diagram illustrating the configuration of a high-frequency module 600 according to Embodiment 6. The high-frequency module 600 comprises a semiconductor chip 80 and semiconductor devices 100, 200, 300, and 400 of any of Embodiments 1 to 4 connected to the semiconductor chip 80, within a package. In other words, the structure for reducing impedance at Δf, as described in Embodiments 1 to 4, is provided as a separate chip from the transistor. The semiconductor devices 100, 200, 300, and 400 in this embodiment are, for example, bare chips. The semiconductor devices 100, 200, 300, and 400 are connected to the pads 81 of the semiconductor chip 80 via wires 85.

[0061] The semiconductor devices 100, 200, 300, and 400 of this embodiment can be used, for example, as capacitors to prevent oscillation at low frequencies. The semiconductor devices 100, 200, 300, and 400 are made of GaN. Therefore, their heat resistance temperature is higher than that of commercially available chip components, which is approximately 125°C. Accordingly, they are suitable for high-power devices used in high-temperature environments. By designing the GaN layers 10 and 210 so that BAW propagates at unstable frequencies, it is possible to contribute to circuit stabilization. The semiconductor devices 100, 200, 300, and 400 of this embodiment may also be used as filter circuits in MMIC, IMFET circuits, etc.

[0062] Alternatively, the semiconductor devices 100, 200, 300, and 400 of Embodiments 1-4 may be mounted on the same chip as the transistors, and the semiconductor devices 100, 200, 300, and 400 may be mounted in a package to constitute a high-frequency module 600.

[0063] The technical features described in each embodiment may be used in combination as appropriate. [Explanation of symbols]

[0064] 10 GaN layer, 12 via hole, 15 BAW propagation section, 21 upper ground electrode, 22 lower ground electrode, 23 wiring, 24 air bridge, 25 metal, 26 back metal, 27 GND metal, 30 SiC substrate, 32 via hole, 41 source electrode, 42 drain electrode, 43 gate electrode, 80 semiconductor chip, 81 pad, 85 wire, 100 semiconductor device, 100a semiconductor device, 200 semiconductor device, 200a semiconductor device, 210 GaN layer, 218 semiconductor layer, 228 covering section, 300 semiconductor device, 300a semiconductor device, 312 via hole, 313 via hole, 314 via hole, 315 wiring, 321 electrode, 322 electrode, 326 back metal, 352 receiving metal, 353 metal, 360 protective film, 362 wiring, 400 Semiconductor equipment, 400a semiconductor equipment, 412 via holes, 422 electrodes, 500 semiconductor equipment, 570 quarter-wavelength stubs, 600 high-frequency modules

Claims

1. A GaN layer having an upper surface and a back surface opposite to the upper surface, and provided with a BAW propagation section configured to propagate BAW of a predetermined frequency in the direction from the upper surface to the back surface, Among the GaN layer, a first via hole is provided around the BAW propagation section, At least one of the GaN layers is provided on the BAW propagation section, and the upper ground electrode is provided on the BAW propagation section. Of the GaN layers, at least the base electrode provided below the BAW propagation portion, Equipped with, A semiconductor device characterized in that there is no metal layer on the inner wall of the first via hole.

2. A GaN layer having an upper surface and a back surface opposite to the upper surface, and provided with a BAW propagation section configured to propagate BAW of a predetermined frequency in the direction from the upper surface to the back surface, Among the GaN layer, a first via hole is provided around the BAW propagation section, At least one of the GaN layers is provided on the BAW propagation section, and the upper ground electrode is provided on the BAW propagation section. Of the GaN layers, at least the base electrode provided below the BAW propagation portion, Equipped with, The semiconductor device is characterized in that the first via hole is provided so as to surround the BAW propagation section.

3. The semiconductor device according to claim 1 or 2, characterized in that the upper ground electrode is provided above the first via hole so as to block the first via hole.

4. A GaN layer having an upper surface and a back surface opposite to the upper surface, and provided with a BAW propagation section configured to propagate BAW of a predetermined frequency in the direction from the upper surface to the back surface, Among the GaN layer, a first via hole is provided around the BAW propagation section, At least one of the GaN layers is provided on the BAW propagation section, and the upper ground electrode is provided on the BAW propagation section. Of the GaN layers, at least the base electrode provided below the BAW propagation portion, Equipped with, A semiconductor device characterized in that the thickness of the GaN layer is 25 μm or more.

5. The semiconductor device according to any one of claims 1, 2, or 4, characterized in that the base electrode is connected to GND metal without going through a semiconductor substrate.

6. A SiC substrate provided on the back surface of the GaN layer, The back metal provided on the side of the SiC substrate opposite to the GaN layer, A second via hole provided in the SiC substrate, Equipped with, The semiconductor device according to claim 1 or 2, characterized in that the base electrode and the back metal are electrically connected by the second via hole.

7. A transistor formed in the GaN layer, The electrodes of the transistor provided on the GaN layer, Equipped with, The semiconductor device according to any one of claims 1, 2, or 4, characterized in that the upper ground electrode is electrically connected to the electrode of the transistor.

8. A GaN layer having an upper surface and a back surface opposite to the upper surface, and provided with a BAW propagation section configured to propagate BAW of a predetermined frequency in the direction from the upper surface to the back surface, Among the GaN layer, a first via hole is provided around the BAW propagation section, At least one of the GaN layers is provided on the BAW propagation section, and the upper ground electrode is provided on the BAW propagation section. Of the GaN layers, at least the base electrode provided below the BAW propagation portion, A stub with a carrier frequency of 1 / 4 wavelength is provided on the GaN layer, Equipped with, A semiconductor device characterized in that the upper ground electrode is connected to the quarter-wavelength stub.

9. Semiconductor chips and A semiconductor device according to any one of claims 1, 2, or 4 connected to the aforementioned semiconductor chip, A high-frequency module characterized by comprising the following features.

10. A GaN layer having an upper surface and a back surface opposite to the upper surface, A first electrode inserted into the GaN layer from the upper surface of the GaN layer, A second electrode is inserted into the GaN layer from the upper or lower surface of the GaN layer and is positioned horizontally offset from the first electrode, Equipped with, The semiconductor device is characterized in that the GaN layer is configured to propagate a BAW of a predetermined frequency in the horizontal direction and in the direction from the first electrode to the second electrode.

11. The semiconductor device according to claim 10, characterized in that it comprises a first via hole provided around the portion of the GaN layer that is sandwiched between the first electrode and the second electrode in a plan view.

12. The semiconductor device according to claim 10 or 11, characterized in that it comprises a second via hole provided directly below the portion of the GaN layer that is sandwiched between the first electrode and the second electrode in a plan view.

13. A protective film is provided on the upper surface of the GaN layer in the portion sandwiched between the first electrode and the second electrode in a plan view, Wiring provided on the protective film, The semiconductor device according to claim 10 or 11, characterized by comprising the above.

14. The semiconductor device according to claim 10 or 11, characterized in that the second electrode is inserted into the GaN layer from the upper surface of the GaN layer.

15. The semiconductor device according to claim 10 or 11, characterized in that the second electrode is inserted into the GaN layer from the back surface of the GaN layer.

16. The semiconductor device according to claim 15, further comprising a third via hole provided in the propagation direction of the BAW, on the opposite side of the second electrode from the first electrode and adjacent to the second electrode.

17. A transistor formed in the GaN layer, The electrodes of the transistor provided on the GaN layer, Equipped with, The semiconductor device according to claim 10 or 11, characterized in that the first electrode is electrically connected to the electrode of the transistor.

18. The GaN layer is provided with a stub that is one-quarter wavelength of the carrier frequency, The semiconductor device according to claim 10 or 11, characterized in that the first electrode is connected to the quarter-wavelength stub.

19. Semiconductor chips and A semiconductor device according to claim 10 or 11 connected to the semiconductor chip, A high-frequency module characterized by comprising the following features.

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