Terahertz device

Abstract

This terahertz device includes: a substrate including a substrate surface; an active element provided on the substrate surface and oscillating or detecting an electromagnetic wave; an antenna electrically connected to the active element; and a circuit member provided on the substrate surface and electrically connected to the antenna. The circuit member includes a curved part curved in a plan view viewed from a Z-axis direction perpendicular to the substrate surface.

Description

Terahertz Device

[0001] The present disclosure relates to terahertz devices.

[0002] In recent years, as electronic devices such as transistors have become increasingly miniaturized and their size has reached nanoscale, a phenomenon known as the quantum effect has become observable. Development is underway to utilize this quantum effect to realize ultrafast devices and devices with new functions.

[0003] In such an environment, attempts are being made to utilize electromagnetic waves in the frequency range known as the terahertz band, which has a frequency range of 0.1 THz to 10 THz, for high-capacity communication, information processing, imaging, measurement, and so on. Electromagnetic waves in this frequency range possess the properties of both light and radio waves. Devices operating in this frequency band can be used for a wide range of applications, including the aforementioned imaging, high-capacity communication, and information processing, as well as measurements in various fields such as physical analysis, astronomy, and biology.

[0004] A terahertz device having an antenna structure and an active element that emits electromagnetic waves in the terahertz band or an active element that detects electromagnetic waves is known (see, for example, Patent Document 1).

[0005] Japanese Patent Application Laid-Open No. 2020-115500

[0006] [Summary] However, components arranged around an active element may generate electromagnetic waves with frequencies different from the desired frequency.

[0007] A terahertz device according to one aspect of the present disclosure includes a substrate having a first surface, an active element provided on the first surface for oscillating or detecting electromagnetic waves, an antenna electrically connected to the active element, and a circuit member provided on the first surface and electrically connected to the antenna, the circuit member including a curved portion that is curved in a planar view when viewed from a direction perpendicular to the first surface.

[0008] FIG. 1 is a schematic perspective view of an exemplary terahertz device according to the first embodiment. FIG. 2 is a schematic plan view showing the terahertz device of FIG. 1. FIG. 3 is a schematic plan view showing an enlarged portion of the terahertz device of FIG. 2. FIG. 4 is a schematic cross-sectional view of the terahertz device taken along line F4-F4 in FIG. 2. FIG. 5 is a schematic cross-sectional view of the active element of FIG. 4. FIG. 6 is a schematic cross-sectional view of the terahertz device taken along line F6-F6 in FIG. 2. FIG. 7 is a schematic cross-sectional view of a terahertz unit illustrating an application example of the terahertz device of FIG. 1. FIG. 8 is a schematic plan view showing a terahertz device of a comparative example. FIG. 9 is a schematic plan view showing the terahertz device of FIG. 2. FIG. 10 is a schematic plan view showing the terahertz device of the comparative example of FIG. 8. FIG. 11 is a characteristic diagram showing the frequency characteristics (admittance: real part) of the terahertz devices of FIGS. 9 and 10. FIG. 12 is a characteristic diagram showing the frequency characteristics (admittance: imaginary part) of the terahertz devices of FIGS. 9 and 10 . FIG. 13 is an explanatory diagram showing a configuration of a pad electrode. FIG. 14 is an explanatory diagram showing an exemplary configuration of a curved portion of a pad electrode. FIG. 15 is an explanatory diagram showing an exemplary configuration of a curved portion of a pad electrode. FIG. 16 is an explanatory diagram showing an exemplary configuration of a curved portion of a pad electrode. FIG. 17 is an explanatory diagram showing an exemplary configuration of a curved portion of a pad electrode. FIG. 18 is an explanatory diagram showing an exemplary configuration of a curved portion of a pad electrode. FIG. 19 is an explanatory diagram showing an exemplary configuration of a curved portion of a pad electrode. FIG. 20 is an explanatory diagram showing an exemplary configuration of a curved portion of a pad electrode. FIG. 21 is a schematic plan view showing a terahertz device of a modified example. FIG. 22 is a schematic plan view showing a terahertz device of a modified example. FIG. 23 is a schematic plan view showing a terahertz device of a modified example. FIG. 24 is a schematic plan view showing a terahertz device of a modified example. FIG. 25 is a schematic plan view showing a terahertz device of a modified example. Fig. 26 is a schematic plan view showing a terahertz device according to a modified example. Fig. 27 is a schematic plan view showing a terahertz device according to a modified example. Fig. 28 is a schematic plan view showing an exemplary terahertz device according to a second embodiment. Fig. 29 is a schematic plan view showing a terahertz device according to a modified example. Fig. 30 is a schematic plan view showing a terahertz device according to a modified example. Fig. 31 is a schematic plan view showing an exemplary terahertz device according to a third embodiment.FIG. 32 is a schematic cross-sectional view of a terahertz unit illustrating an application example of the terahertz device of FIG. 31 . FIG. 33 is a schematic plan view illustrating a modified terahertz device. FIG. 34 is a schematic plan view illustrating a modified terahertz device. FIG. 35 is a schematic perspective view of an exemplary terahertz device according to a fourth embodiment. FIG. 36 is a schematic plan view illustrating the terahertz device of FIG. 35 . FIG. 37 is a schematic plan view illustrating some components of the terahertz device of FIG. 36 . FIG. 38 is a schematic cross-sectional view of the terahertz device taken along line F38-F38 in FIG. 36 . FIG. 39 is a schematic plan view illustrating the active element of FIG. 36 and its periphery. FIG. 40 is a schematic plan view illustrating the active element of FIG. 36 and its periphery. FIG. 41 is a schematic cross-sectional view illustrating the active element of FIG. 36 and its periphery. FIG. 42 is a schematic plan view illustrating the resistive element of FIG. 36 and its periphery. FIG. 43 is a schematic cross-sectional view illustrating the resistive element of FIG. 36 and its periphery. FIG. 44 is a schematic plan view illustrating a modified terahertz device. FIG. 45 is a schematic plan view showing a terahertz device according to a modified example. FIG. 46 is a schematic plan view showing a terahertz device according to a modified example. FIG. 47 is a schematic plan view showing a terahertz device according to a modified example. FIG. 48 is a schematic plan view showing a terahertz device according to a modified example. FIG. 49 is a schematic plan view showing a terahertz device according to a modified example. FIG. 50 is a schematic plan view of an exemplary terahertz device according to a fifth embodiment. FIG. 51 is a schematic plan view showing an active element of FIG. 50 and its periphery. FIG. 52 is a schematic plan view showing the active element of FIG. 50 and its periphery. FIG. 53 is a schematic cross-sectional view showing the active element of FIG. 50 and its periphery. FIG. 54 is a schematic plan view of an exemplary terahertz device according to a sixth embodiment. FIG. 55 is a schematic plan view showing a terahertz device according to a modified example. FIG. 56 is a schematic plan view showing a terahertz device according to a modified example.

[0009] DETAILED DESCRIPTION Hereinafter, several embodiments of the terahertz device of the present disclosure will be described with reference to the accompanying drawings. Note that for simplicity and clarity of description, components shown in the drawings are not necessarily drawn to scale. Also, for ease of understanding, hatching lines may be omitted in cross-sectional views. The accompanying drawings merely illustrate embodiments of the present disclosure and should not be considered to limit the present disclosure. Terms such as "first," "second," and "third" in the present disclosure are used merely to distinguish between objects and not to rank them.

[0010] The following detailed description includes devices, systems, and methods embodying exemplary embodiments of the present disclosure. This detailed description is merely illustrative in nature and is not intended to limit the embodiments of the present disclosure or the application and uses of such embodiments.

[0011] The phrase "at least one" as used in this disclosure means "one or more" of the desired options. As an example, the phrase "at least one" as used in this disclosure means "only one option" or "both of two options" when the number of options is two. As another example, the phrase "at least one" as used in this disclosure means "only one option" or "any combination of two or more options" when the number of options is three or more.

[0012] (First embodiment) A terahertz device 10 according to a first embodiment will be described with reference to Fig. 1 to Fig. 6. (Schematic configuration of terahertz device) Fig. 1 is a schematic perspective view of an exemplary terahertz device 10 according to a first embodiment. Fig. 2 is a schematic plan view of the terahertz device 10 of Fig. 1. Fig. 3 is a schematic plan view enlarging a portion of the terahertz device 10 of Fig. 2. Note that the term "plan view" used in this disclosure refers to viewing the terahertz device 10 in the Z-axis direction of the mutually orthogonal X, Y and Z axes shown in Fig. 1.

[0013] As shown in FIGS. 1 to 3 , the terahertz device 10 of the first embodiment has a rectangular parallelepiped shape. The terahertz device 10 includes a substrate 100. The substrate 100 has a flat plate shape. The substrate 100 may include a semiconductor substrate. The substrate 100 may be made of a semiconductor substrate. The semiconductor substrate may be made of at least one semiconductor material selected from the group consisting of InP (indium phosphide), GaAs (gallium arsenide), AlGaAs (aluminum gallium arsenide), InGaAs (indium gallium arsenide), InGaAsP (indium gallium arsenide phosphide), Si (silicon), SiC (silicon carbide), GaN (gallium nitride), and single-crystal AlN (aluminum nitride). In one example, the substrate 100 may be made of a material containing InP.

[0014] As shown in Figures 1 and 2, the substrate 100 has a rectangular parallelepiped shape. The substrate 100 includes a substrate front surface 101 and a substrate back surface 102 opposite the substrate front surface 101. The substrate front surface 101 corresponds to the first surface of the substrate 100. The substrate 100 also includes a plurality of substrate side surfaces 103, 104, 105, and 106 that connect the substrate front surface 101 and the substrate back surface 102. The substrate side surfaces 103 to 106 face either the X-axis direction or the Y-axis direction. The substrate side surfaces 103 and 105 extend along the XZ plane. The substrate side surfaces 103 and 105 constitute both end surfaces in the Y-axis direction. The substrate side surfaces 104 and 106 extend along the YZ plane. The substrate side surfaces 104 and 106 constitute both end surfaces in the X-axis direction.

[0015] In a plan view, the substrate surface 101 of the substrate 100 has a rectangular shape including four corners 111, 112, 113, and 114. The first corner 111 is formed by the substrate side surface 103 and the substrate side surface 104. The second corner 112 is formed by the substrate side surface 104 and the substrate side surface 105. The third corner 113 is formed by the substrate side surface 105 and the substrate side surface 106. The fourth corner 114 is formed by the substrate side surface 106 and the substrate side surface 103.

[0016] The terahertz device 10 includes an insulating layer 120. The insulating layer 120 is provided on a substrate 100. The insulating layer 120 covers a portion of the substrate surface 101 of the substrate 100. In one example, the insulating layer 120 covers a central portion of the substrate surface 101. The insulating layer 120 is disposed in the central portion of the substrate surface 101 in the X-axis direction and the Y-axis direction. In one example, the insulating layer 120 can be said to cover an area of ​​the substrate surface 101 where the antenna 150 and the like are disposed. In a plan view, the insulating layer 120 may have a rectangular shape. The insulating layer 120 may cover the entire substrate surface 101. The insulating layer 120 is made of an insulating material. The insulating layer 120 is made of a material containing, for example, silicon oxide (SiO2). The insulating layer 120 includes an insulating surface 121 and an insulating back surface 122 opposite the insulating surface 121. The insulating back surface 122 of the insulating layer 120 is in contact with the substrate front surface 101 of the substrate 100 .

[0017] The terahertz device 10 includes an active element 130 and an antenna 150. The active element 130 is disposed on a substrate surface 101 of a substrate 100. In one example, the active element 130 has a rectangular shape in a planar view. Note that the shape of the active element 130 in a planar view is not limited to a rectangular shape, and may be any of a circular shape, an elliptical shape, and a polygonal shape.

[0018] The active element 130 is an element that converts electromagnetic waves into electrical energy. Note that the term "electromagnetic waves" encompasses the concepts of either light or radio waves, or both. The active element 130 is an element that oscillates electromagnetic waves (terahertz waves) in a predetermined frequency band, for example, the terahertz band. In this case, the active element 130 can be said to be a terahertz element that oscillates terahertz waves. Furthermore, for example, the active element 130 is an element that detects terahertz waves, which are electromagnetic waves in a predetermined frequency band, for example, the terahertz band. In this case, the active element 130 can be said to be a terahertz element that receives terahertz waves. Here, the frequency band of the terahertz waves is, for example, 0.1 THz or more and 10 THz or less.

[0019] Active element 130 converts the supplied electrical energy into electromagnetic waves by oscillating with the supplied electrical energy. As a result, active element 130 oscillates electromagnetic waves in a desired frequency band. Active element 130 also receives electromagnetic waves and converts the electromagnetic waves into electrical energy. As a result, active element 130 detects electromagnetic waves in a desired frequency band.

[0020] The antenna 150 is disposed on the substrate surface 101 of the substrate 100. In one example, the antenna 150 is configured as a dipole antenna. More specifically, the antenna 150 includes a first antenna member 151 and a second antenna member 152 extending in opposite directions in the X-axis direction. In one example, the first antenna member 151 and the second antenna member 152 may be disposed at the center of the substrate 100 in the Y-axis direction. The first antenna member 151 and the second antenna member 152 are disposed spaced apart from each other in the X-axis direction. The first antenna member 151 is disposed closer to the substrate side surface 104 than the second antenna member 152. The second antenna member 152 is disposed closer to the substrate side surface 106 than the first antenna member 151.

[0021] The length L11 of the antenna 150, i.e., the length in the X-axis direction from the tip 151A of the first antenna member 151 to the tip 152A of the second antenna member 152, may be set, for example, according to the wavelength λ of the electromagnetic wave generated by the active element 130. In one example, the length L11 of the antenna 150 may be set to ½ wavelength (λ / 2) of the wavelength λ of the electromagnetic wave generated by the active element 130. The wavelength λ may be the effective wavelength of the electromagnetic wave propagating inside the terahertz device 10.

[0022] The antenna 150 is electrically connected to the active element 130. When the active element 130 oscillates electromagnetic waves, the antenna 150 radiates the electromagnetic waves from the active element 130 to the outside of the terahertz device 10. When the active element 130 detects electromagnetic waves, the antenna 150 receives the electromagnetic waves incident from the outside of the terahertz device 10. The antenna 150 is made of at least one metal material selected from the group consisting of Au, Ag, Al, Cu, Ti, TiN, and Pt. In one example, the antenna 150 is made of a material containing Au.

[0023] The terahertz device 10 includes a circuit member 160 electrically connected to the antenna 150. The circuit member 160 is used to apply a voltage to the active element 130 or to transmit a signal detected by the active element 130.

[0024] The circuit member 160 includes a first pad electrode 171 and a second pad electrode 172. The first pad electrode 171 and the second pad electrode 172 are arranged on either side of the antenna 150. The first pad electrode 171 and the second pad electrode 172 are arranged symmetrically with respect to the antenna 150. The first pad electrode 171 and the second pad electrode 172 are electrically connected to the antenna 150. In one example, the first pad electrode 171 is electrically connected to a first antenna member 151 of the antenna 150, and the second pad electrode 172 is electrically connected to a second antenna member 152 of the antenna 150.

[0025] The first pad electrode 171 and the second pad electrode 172 are arranged at the edge of the substrate 100. In one example, the first pad electrode 171 is arranged on the substrate surface 101 of the substrate 100, closer to the substrate side surface 103 of the substrate 100. In one example, the first pad electrode 171 is arranged in the center of the substrate surface 101 in the X-axis direction. The first pad electrode 171 has a circular shape in a planar view. It can be said that the first pad electrode 171 includes a curved portion 230 over the entire end portion. In other words, it can be said that the circuit member 160 includes a curved portion 230 that is curved in a planar view.

[0026] The width W11 of the first pad electrode 171 may be represented by a diameter in the X-axis direction, for example. The width W11 of the first pad electrode 171 may be smaller than the length L11 of the antenna 150. The first pad electrode 171 is made of at least one metal material selected from the group consisting of Au, Ag, Al, Cu, Ti, TiN, and Pt. For example, the first pad electrode 171 is made of a material containing Au.

[0027] The second pad electrode 172 is arranged on the substrate surface 101 of the substrate 100, closer to the substrate side surface 105 of the substrate 100. In one example, the second pad electrode 172 is arranged in the center of the substrate surface 101 in the X-axis direction. In one example, the first pad electrode 171 and the second pad electrode 172 are arranged on a straight line that passes through the active element 130 and extends in the Y-axis direction. The second pad electrode 172 has a circular shape in a planar view. It can be said that the second pad electrode 172 includes a curved portion 230 over the entire end portion. In other words, it can be said that the circuit member 160 includes a curved portion 230 that is curved in a planar view.

[0028] The width W12 of the second pad electrode 172 may be represented by a diameter in the X-axis direction, for example. The width W12 of the second pad electrode 172 may be smaller than the length L11 of the antenna 150. The width W12 of the second pad electrode 172 may be equal to or different from the width W11 of the first pad electrode 171. The second pad electrode 172 is made of at least one metal material selected from the group consisting of Au, Ag, Al, Cu, Ti, TiN, and Pt. For example, the second pad electrode 172 is made of a material containing Au.

[0029] The circuit member 160 may include a first capacitor 181 and a second capacitor 182. The first capacitor 181 is disposed between the antenna 150 and the first pad electrode 171. The second capacitor 182 is disposed between the antenna 150 and the second pad electrode 172.

[0030] First capacitor 181 and second capacitor 182 include first electrode plate 183 and second electrode plate 184, respectively. First electrode plate 183 and second electrode plate 184 may have the same shape as each other in a plan view. In FIGS. 2 and 3 , second electrode plate 184 is depicted smaller than first electrode plate 183 in order to illustrate second electrode plate 184. In one example, first electrode plate 183 and second electrode plate 184 may have a rectangular shape in which the length in the Y-axis direction is greater than the length in the X-axis direction. First electrode plate 183 and second electrode plate 184 face each other with insulating layer 120 sandwiched therebetween.

[0031] The first electrode plate 183 and the second electrode plate 184 are made of at least one metal material selected from the group consisting of Au, Ag, Al, Cu, Ti, TiN, and Pt. In one example, the first electrode plate 183 and the second electrode plate 184 are made of a material containing Au. The first electrode plate 183 and the second electrode plate 184 are made of a metal layer. Therefore, the first capacitor 181 and the second capacitor 182 can be called MIM (Metal-Insulator-Metal) capacitors.

[0032] The planar shape of the first electrode plate 183 will be described in detail with reference to FIG. 3. Note that the second electrode plate 184 has the same shape as the first electrode plate 183, and therefore a detailed description thereof will be omitted. The first electrode plate 183 has a rectangular shape with rounded corners. The first electrode plate 183 has a rectangular shape in plan view. The first electrode plate 183 has a rectangular shape including four corner portions 191 to 194. The first electrode plate 183 includes curved portions 230. The curved portions 230 are provided at each of the four corner portions 191 to 194. In other words, it can be said that the circuit member 160 includes curved portions 230 that are curved in plan view.

[0033] The first electrode plate 183 includes a first corner portion 191 and a second corner portion 192 that is positioned closer to the active element 130 than the first corner portion 191. The first electrode plate 183 also includes a third corner portion 193 that is diagonally opposite the first corner portion 191, and a fourth corner portion 194 that is diagonally opposite the second corner portion 192. A curved portion 230 is provided in each of the first to fourth corner portions 191 to 194.

[0034] 2 and 3 , the circuit member 160 includes a first wiring member 200 that electrically connects the first pad electrode 171 and the first antenna member 151. The circuit member 160 also includes a second wiring member 210 that electrically connects the second pad electrode 172 and the second antenna member 152. The first wiring member 200 and the second wiring member 210 are made of at least one metal material selected from the group consisting of Au, Ag, Al, Cu, Ti, TiN, and Pt. In one example, the first wiring member 200 and the second wiring member 210 are made of a material containing Au.

[0035] The first capacitor 181 and the second capacitor 182 are electrically connected between the first wiring member 200 and the second wiring member 210. The first electrode plate 183 of the first capacitor 181 is electrically connected to the first wiring member 200, and the second electrode plate 184 of the first capacitor 181 is electrically connected to the second wiring member 210. The first electrode plate 183 of the second capacitor 182 is electrically connected to the second wiring member 210, and the second electrode plate 184 of the second capacitor 182 is electrically connected to the first wiring member 200.

[0036] The circuit member 160 may include a first resistor element 221 and a second resistor element 222. The first resistor element 221 is disposed between the first capacitor 181 and the first pad electrode 171. The second resistor element 222 is disposed between the second capacitor 182 and the second pad electrode 172. The first resistor element 221 and the second resistor element 222 may be formed of a semiconductor layer containing impurities. For example, the impurities may be n-type impurities. The first resistor element 221 and the second resistor element 222 may be formed of a semiconductor layer doped with a high concentration of n-type impurities. For example, the semiconductor layer may be GaInAs.

[0037] The first resistor element 221 and the second resistor element 222 are electrically connected between the first antenna member 151 and the second antenna member 152. The first resistor element 221 and the second resistor element 222 are electrically connected between the first wiring member 200 and the second wiring member 210. The first resistor element 221 and the second resistor element 222 are electrically connected in parallel to the active element 130. The first resistor element 221 and the second resistor element 222 suppress parasitic oscillation. This allows the terahertz device 10 to stabilize oscillation.

[0038] The first wiring member 200 includes a first wiring portion 201, a second wiring portion 202, and a third wiring portion 203. The first wiring portion 201 electrically connects the first pad electrode 171 and the first electrode plate 183 of the first capacitor 181. The second wiring portion 202 electrically connects the first electrode plate 183 of the first capacitor 181, the first antenna member 151 of the antenna 150, and the second electrode plate 184 of the second capacitor 182. The third wiring portion 203 electrically connects the second electrode plate 184 of the second capacitor 182 and the second resistor element 222. The second resistor element 222 is electrically connected between the third wiring portion 203 of the first wiring member 200 and the first wiring portion 211 of the second wiring member 210.

[0039] The second wiring member 210 includes a first wiring portion 211, a second wiring portion 212, and a third wiring portion 213. The first wiring portion 211 electrically connects the second pad electrode 172 and the first electrode plate 183 of the second capacitor 182. The second wiring portion 212 electrically connects the first electrode plate 183 of the second capacitor 182, the second antenna member 152 of the antenna 150, and the second electrode plate 184 of the first capacitor 181. The third wiring portion 213 electrically connects the second electrode plate 184 of the first capacitor 181 and the first resistor element 221. The first resistor element 221 is electrically connected between the third wiring portion 213 of the second wiring member 210 and the first wiring portion 201 of the first wiring member 200.

[0040] The first wiring member 200 has a first wiring width W31. The first wiring width W31 is smaller than the first pad width W11 of the first pad electrode 171. The first wiring width W31 is also smaller than the first electrode width W21 of the first capacitor 181. The second wiring member 210 has a second wiring width W32. The second wiring width W32 is smaller than the second pad width W12 of the second pad electrode 172. The second wiring width W32 is also smaller than the second electrode width W22 of the second capacitor 182. The first wiring width W31 of the first wiring member 200 may be equal to or different from the second wiring width W32 of the second wiring member 210. The first pad width W11 of the first pad electrode 171 may be equal to or different from the second pad width W12 of the second pad electrode 172. The first electrode width W21 of the first capacitor 181 may be equal to or different from the second electrode width W22 of the second capacitor 182.

[0041] 1 and 3 , the terahertz device 10 may include a back surface metal layer 125. The back surface metal layer 125 is provided on the back surface 102 of the substrate 100. The back surface metal layer 125 is in contact with the back surface 102 of the substrate 100. The back surface metal layer 125 includes a reflective surface 126 and a reflective back surface 127 opposite to the reflective surface 126.

[0042] The back surface metal layer 125 may cover at least a portion of the back surface 102 of the substrate 100. The back surface metal layer 125 may be arranged so as to overlap the antenna 150 in a plan view. In one example, the back surface metal layer 125 is provided over the entire back surface 102 of the substrate 100. It can be said that the back surface metal layer 125 covers the entire back surface 102 of the substrate 100. The back surface metal layer 125 may have a thickness that allows it to reflect electromagnetic waves generated or detected by the active element 130. The back surface metal layer 125 may be said to be a reflective layer that reflects electromagnetic waves.

[0043] The back surface metal layer 125 is composed of a metal layer provided on the back surface 102 of the substrate 100. The back surface metal layer 125 is composed of at least one metal material selected from the group consisting of Au, Ag, Al, Cu, Ti, TiN, and Pt. It can also be said that the back surface metal layer 125 contains at least one of Au, Ag, Al, Cu, Ti, and Pt. In one example, the back surface metal layer 125 is composed of a material containing Au. The back surface metal layer 125 may be composed of the same material as the antenna 150. The back surface metal layer 125 may also be composed of a stacked structure of multiple metal layers.

[0044] (Outline of Active Element) As shown in FIG. 1 , the active element 130 is provided at the center of the substrate surface 101 in the X-axis direction and the Y-axis direction. For example, the active element 130 is an element that exchanges electromagnetic waves of a predetermined frequency band with electrical energy, and therefore converts electrical energy supplied from the first pad electrode 171 and the second pad electrode 172 into electromagnetic waves of a predetermined frequency band. The electromagnetic waves from the active element 130 are radiated by the antenna 150. Therefore, the active element 130 can be referred to as an oscillation point P1 that oscillates electromagnetic waves, and the antenna 150 can be referred to as a radiation point P2 that radiates electromagnetic waves. In this embodiment, the radiation point P2 and the oscillation point P1 are located at the same position. Note that the position of the oscillation point P1 is not limited to the same position as the radiation point P2 and can be arbitrarily changed. Furthermore, the position of the oscillation point P1 can be located at any position on the substrate surface 101 when viewed from the Z-axis direction.

[0045] The active element 130 is, for example, a resonant tunneling diode (RTD). The active element 130 may also be, for example, a tunnel injection transit time (TUNNETT) diode, an impact ionization avalanche transit time (IMPATT) diode, a GaAs-based field effect transistor (FET), a GaN-based FET, a high electron mobility transistor (HEMT), a heterojunction bipolar transistor (HBT), a complementary metal-oxide-semiconductor (CMOS) FET, or a Schottky barrier diode (SBD).

[0046] (Detailed configuration of active element and its periphery) Fig. 4 shows an example of the connection between the active element 130 and the antenna 150. Fig. 5 shows an example of the configuration of the active element 130. Fig. 6 shows an example of the configuration of the first capacitor 181 and the second capacitor 182.

[0047] As shown in Fig. 4, the active element 130 is provided between the first antenna member 151 and the substrate 100. As shown in Figs. 4 and 5, a semiconductor layer 141A is provided on the substrate surface 101 of the substrate 100. In one example, the semiconductor layer 141A has a rectangular shape when viewed from the Z-axis direction. The semiconductor layer 141A is made of, for example, GaInAs. The semiconductor layer 141A is heavily doped with n-type impurities.

[0048] 5, a GaInAs layer 142A is stacked on a semiconductor layer 141A. The GaInAs layer 142A is doped with n-type impurities. The n-type impurity concentration of the GaInAs layer 142A is lower than the n-type impurity concentration of the semiconductor layer 141A.

[0049] A GaInAs layer 143A is stacked on the GaInAs layer 142A. The GaInAs layer 143A is not doped with impurities. An AlAs layer 144A is stacked on the GaInAs layer 143A. An InGaAs layer 145 is stacked on the AlAs layer 144A. The InGaAs layer 145 is not doped with impurities. An AlAs layer 144B is stacked on the InGaAs layer 145. The AlAs layer 144A, the InGaAs layer 145, and the AlAs layer 144B form a resonant tunnel section.

[0050] An undoped GaInAs layer 143B is stacked on the AlAs layer 144B. An n-type impurity-doped GaInAs layer 142B is stacked on the GaInAs layer 143B. A highly doped GaInAs layer 141B is stacked on the GaInAs layer 142B. Therefore, the n-type impurity concentration of the GaInAs layer 141B is higher than that of the GaInAs layer 142B.

[0051] The specific configuration of the active element 130 can be changed as desired as long as it can generate (or detect, or both) electromagnetic waves. In other words, the active element 130 may be any element that performs at least one of oscillation and detection of electromagnetic waves in the terahertz band.

[0052] 4, the first antenna member 151 includes a first antenna body 151B provided on the insulating layer 120 and a first connection portion 151C connected to the active element 130. The second antenna member 152 includes a second antenna body 152B provided on the insulating layer 120 and a second connection portion 152C connected to the semiconductor layer 141A.

[0053] 6 , the second electrode plate 184 is provided on the substrate surface 101 of the substrate 100. The second electrode plate 184 is covered with the insulating layer 120. The first electrode plate 183 is provided on the insulating layer 120. In this manner, the first electrode plate 183 and the second electrode plate 184 are disposed opposite each other in the Z-axis direction with the insulating layer 120 sandwiched therebetween. The first capacitor 181 and the second capacitor 182 short-circuit the first pad electrode 171 and the second pad electrode 172 at high frequencies. The first capacitor 181 and the second capacitor 182 can reflect high-frequency electromagnetic waves and therefore function as low-pass filters.

[0054] 3 , the second electrode plate 184 of the first capacitor 181 is electrically connected to the second wiring member 210 (second connection portion 212, third connection portion 213) disposed on the insulating layer 120 by vias 214. The second electrode plate 184 of the second capacitor 182 is electrically connected to the first wiring member 200 (second connection portion 202, third connection portion 203) disposed on the insulating layer 120 by vias 204.

[0055] (Curved Portion) Next, several examples of the curved portion 230 will be described in detail. FIG. 13 is a schematic plan view of a conductive layer 240 for illustrating the curved portion 230. The conductive layer 240 may schematically represent the first pad electrode 171 and the second pad electrode 172 shown in FIG. 2. The conductive layer 240 may also schematically represent the electrode plates 183, 184 of the first capacitor 181 and the second capacitor 182 shown in FIG. 2. The conductive layer 240 may correspond to the first pad electrode 171 and the second pad electrode 172. The conductive layer 240 may also correspond to the first electrode plate 183 and the second electrode plate 184 of the first capacitor 181 and the second capacitor 182.

[0056] The conductive layer 240 has a rectangular shape in a plan view. A surface 241 of the conductive layer 240 includes first to fourth sides 251 to 254. The first side 251 and the third side 253 extend in the X-axis direction. The second side 252 and the fourth side 254 extend in the Y-axis direction. In one example, the conductive layer 240 may be the first pad electrode 171 shown in FIG. 2. The conductive layer 240 is disposed with respect to the antenna 150 shown in FIG. 2 such that the third side 253 is closer to the antenna 150 than the first side 251. In other words, it can be said that the conductive layer 240 includes the third side 253 that is closer to the antenna 150 than the first side 251.

[0057] The conductive layer 240 includes four corner portions 261 to 264 formed by first to fourth sides 251 to 254. The first corner portion 261 is formed by the first side 251 and the second side 252. The second corner portion 262 is formed by the second side 252 and the third side 253. The third corner portion 263 is formed by the third side 253 and the fourth side 254. The fourth corner portion 264 is formed by the fourth side 254 and the first side 251.

[0058] The conductive layer 240 includes a curved portion 230 at each of the four corner portions 261 to 264. The curved portion 230 may be provided at the end of the conductive layer 240. The curved portion 230 may be curved so as to be convex toward the outside of the conductive layer 240. The curved portion 230 may be an arc-shaped portion that is convex toward the outside of the conductive layer 240. The size of the curved portion 230 may be changed as appropriate. In one example, the curved portion 230 may be formed around at least half the circumference of the conductive layer 240. In this case, the conductive layer 240 may be said to include a semicircular portion in a planar view. The curved portion 230 may be provided around the entire circumference of the conductive layer 240. In other words, the first to fourth sides 251 to 254 may be omitted. In this case, the shape of the conductive layer 240 in a planar view may be circular. That is, the first pad electrode 171 and the second pad electrode 172 shown in FIGS. 2 and 3 may be an example in which the curved portion 230 is provided over the entire periphery.

[0059] In one example, the first to fourth sides 251 to 254 between the curved portion 230 are straight. At least one of the first to fourth sides 251 to 254 may be curved. In one example, the first to fourth sides 251 to 254 may be curved so as to be convex toward the outside of the conductive layer 240. The radius of curvature of the curved first to fourth sides 251 to 254 may be larger than the radius of curvature of the curved portion 230.

[0060] 13, the curved portion 230 may be represented by a line segment between any two points PA and PB on the periphery of the conductive layer 240. The line segment between the two points PA and PB may include one or more straight lines, curved lines, or both straight lines and curved lines.

[0061] For example, if the line segment 271 between the two points PA and PB is not a straight line, the line segment 271 may be considered to be the curved portion 230. As shown in FIG. 14 , the two points PA and PB, which are at a distance LP, are connected by a line segment 272. The distance LP is set to 1 / m of the effective wavelength of the electromagnetic wave propagating inside the terahertz device 10. In one example, the distance LP may be 1 / 16 of the effective wavelength of the electromagnetic wave. The line segment 272 is formed by two straight lines 272A and 272B connecting the two points PA and PB. If the angle between the two straight lines 272A and 272B is not a right angle, the line segment 272 formed by the two points PA and PB may be considered to be the curved portion 230.

[0062] 15, two points PA and PB at a distance LP are connected by a line segment 273. The first derivative of this line segment 273 has one or less extreme value. This line segment 273 can be said to be the curved portion 230.

[0063] As shown in FIG. 16 , two points PA and PB, which are at a distance LP, are connected by a line segment 274. The line segment 274 is composed of three line segments 274A, 274B, and 274C that connect the two points PA and PB. Each of the line segments 274A, 274B, and 274C may have a length not exceeding 1 / k (k is a positive number greater than m) of the effective wavelength of the electromagnetic wave. In this case, the angle between the line segment 274A and the line segment 274B may include a right angle. Furthermore, the angle between the line segment 274B and the line segment 274C may include a right angle. This line segment 274 may be referred to as the curved portion 230.

[0064] As shown in Figures 17 and 18, two points PA and PB at a distance LP are connected by line segments 275 and 276. These line segments 275 and 276 have extrema where the value of the first derivative exceeds 1. The line segment 275 shown in Figure 17 has two extrema. The line segment 276 shown in Figure 18 has three extrema. These line segments 275 and 276 can be said to be curved portions 230.

[0065] As shown in FIG. 19 , two points PA and PB at a distance LP are connected by a line segment 277. This line segment 277 is composed of multiple segments 277S. The point between two adjacent segments 277S can be said to be an inflection point of the line segment 277. It can be said that the line segment 277 includes multiple inflection points. The angle between two adjacent segments 277S may or may not be a right angle. Each segment 277S may have a length not exceeding 1 / k (k is a positive number greater than m) of the effective wavelength of the electromagnetic wave. Such a line segment 277 can be said to be a curved portion 230.

[0066] 19 may be shown as an envelope 277F at two points PA and PB. This envelope 277F is shown as a curved line segment between two points PA and PB. Such line segment 277 and envelope 277F may be said to be a curved portion 230.

[0067] As shown in FIG. 20 , two points PA and PB, which are at a distance LP, are connected by a line segment 278. The line segment 278 may be expressed as a line segment that continuously oscillates between the two points PA and PB. Such a line segment 278 may be referred to as the curved portion 230. Furthermore, an envelope 278F for this line segment 278 is shown as a curved line segment between the two points PA and PB. Such a line segment 278 and envelope 278F may be referred to as the curved portion 230.

[0068] (Application Example of Terahertz Device) FIG. 7 shows a schematic cross section of a terahertz unit 800 to which the terahertz device 10 of the first embodiment is applied.

[0069] The terahertz unit 800 includes the terahertz device 10, a support substrate 810, and an insulating section 820. The support substrate 810 has a rectangular plate shape. The support substrate 810 is made of an insulating material. An example of the insulating material is epoxy resin. The insulating material may contain a filler such as glass. In one example, the support substrate 810 may be a glass epoxy substrate. The support substrate 810 includes a substrate surface 811 and a substrate back surface 812 opposite to the substrate surface 811.

[0070] Two power feed lines 813 are arranged on a substrate surface 811. Two external electrodes 814 are provided on a substrate back surface 812. Two connection conductors 815 are provided within the support substrate 810 to individually connect the two power feed lines 813 and the two external electrodes 814. The terahertz device 10 is mounted on the substrate surface 811. The first pad electrode 171 and the second pad electrode 172 of the terahertz device 10 are individually electrically connected to the two power feed lines 813 by wires 816.

[0071] The terahertz device 10 is mounted with the rear surface 102 of the substrate 100 facing the substrate surface 811 of the support substrate 810. The terahertz device 10 is attached to the support substrate 810 in a state where the rear surface 102 of the substrate 100 is in contact with the substrate surface 811 of the support substrate 810, or in a state where the rear surface 102 of the substrate 100 faces the substrate surface 811 with an intermediate layer sandwiched therebetween.

[0072] The insulating portion 820 is provided on a substrate surface 811 of the support substrate 810. The insulating portion 820 is made of, for example, resin. In one example, the insulating portion 820 is made of epoxy resin. In one example, the insulating portion 820 has a rectangular parallelepiped shape. The insulating portion 820 includes a surface 823 opposite to the support substrate 810.

[0073] The insulating portion 820 includes a through hole 821 that penetrates the insulating portion 820 in the Z-axis direction. The support substrate 810 covers one opening of the through hole 821 in the Z-axis direction. The insulating portion 820 houses the terahertz device 10. When viewed from the Z-axis direction, the terahertz device 10 is disposed within the through hole 821. It can be said that the insulating portion 820 includes the through hole 821 that houses the terahertz device 10. The through hole 821 functions as a transmission region 822 that transmits electromagnetic waves. The insulating portion 820 includes an inner surface 824 that constitutes the through hole 821. The transmission region 822 is defined by the inner surface 824 of the through hole 821. It can also be said that the terahertz device 10 is disposed within the transmission region 822.

[0074] In one example, the shape of the through hole 821 when viewed from the Z-axis direction is circular. The through hole 821 has a tapered shape that increases in diameter as it moves away from the support substrate 810 in the Z-axis direction. In other words, the through hole 821 has a tapered shape that increases in diameter as it moves away from the terahertz device 10 in the Z-axis direction. The shape of the through hole 821 can be changed as desired. The shape of the through hole 821 when viewed from the Z-axis direction may be a polygon such as a rectangle. The inner surface 824 is inclined with respect to the Z-axis direction. The through hole 821 may have a partially tapered shape. In one example, the inner surface 824 may be provided closer to the support substrate 810 and include a first side surface extending in the Z-axis direction and a second side surface that increases in diameter from the first side surface toward the surface 823. A metal layer may be provided on the inner surface 824. The metal layer may be a plated layer. The metal layer efficiently reflects terahertz waves.

[0075] Comparative Example FIG. 8 shows a terahertz device 10X as a comparative example to the terahertz device 10 of the first embodiment.

[0076] In the terahertz device 10X of the comparative example shown in Fig. 8, the same names and symbols are used for components corresponding to those of the terahertz device 10 of the first embodiment shown in Fig. 2. In the terahertz device 10X of the comparative example, the first pad electrode 171 and the second pad electrode 172 have a rectangular shape with right-angled corners in a plan view. Also, in the terahertz device 10X of the comparative example, the first electrode plate 183 and the second electrode plate 184 of the first capacitor 181 and the second capacitor 182 have a rectangular shape with right-angled corners in a plan view, i.e., without a curved portion 230.

[0077] (Operation of First Embodiment) The terahertz device 10 of the first embodiment includes a substrate 100 including a substrate surface 101, an active element 130 provided on the substrate surface 101 and configured to oscillate or detect electromagnetic waves, an antenna 150 electrically connected to the active element 130, and a circuit member 160 provided on the substrate surface 101 and electrically connected to the antenna 150. The circuit member 160 includes a curved portion 230 that is curved in a planar view when viewed from the Z-axis direction perpendicular to the substrate surface 101.

[0078] The circuit member 160 includes a first pad electrode 171 and a second pad electrode 172 electrically connected to the antenna 150. The first pad electrode 171 and the second pad electrode 172 are used to apply a voltage to the active element 130 or to transmit a signal detected by the active element 130. The first pad electrode 171 and the second pad electrode 172 have a circular shape in a plan view.

[0079] 9 and 10 are schematic plan views showing simulation models. Fig. 9 is a simulation model corresponding to the terahertz device 10 of the first embodiment shown in Fig. 2, and Fig. 10 is a simulation model corresponding to the terahertz device 10X of the comparative example shown in Fig. 8. The terahertz device 10 of Fig. 9 includes an antenna 150, a first pad electrode 171, and a second pad electrode 172. Similarly, the terahertz device 10X of Fig. 10 includes an antenna 150, a first pad electrode 171X, and a second pad electrode 172X.

[0080] In the terahertz device 10X of the comparative example shown in FIG. 10 , the electric field is strongly concentrated at the corners of the first pad electrode 171X and the second pad electrode 172X, compared to the terahertz device 10 shown in FIG. 9 . In this manner, electromagnetic waves are likely to be reflected in the areas where the electric field is concentrated. Therefore, multiple resonant modes are likely to occur within the terahertz device 10. In other words, the terahertz device 10 shown in FIG. 9 is less likely to generate multiple resonant modes than the terahertz device 10X of the comparative example shown in FIG. 10 . In other words, the terahertz device 10X of the comparative example shown in FIG. 10 is more likely to generate electromagnetic waves of frequencies other than the target frequency than the terahertz device 10 shown in FIG. 9 . In other words, the terahertz device 10 shown in FIG. 9 is less likely to generate electromagnetic waves of frequencies other than the target frequency than the terahertz device 10X of the comparative example shown in FIG. 10 .

[0081] 11 and 12 show the frequency characteristics of the terahertz device 10 of FIG. 9 and the terahertz device 10X of FIG. 10. In FIG. 11, the horizontal axis represents frequency, and the vertical axis represents the real part Re[Y] of the admittance of the terahertz device. In FIG. 12, the horizontal axis represents frequency, and the vertical axis represents the imaginary part Im[Y] of the admittance. In FIGS. 11 and 12, the solid line represents the frequency characteristics of the terahertz device 10 of FIG. 9, and the dashed line represents the frequency characteristics of the terahertz device 10X of FIG. 10.

[0082] In the frequency characteristics shown in FIG. 12 , resonance is likely to occur at or near frequency f1, where the imaginary part Im[Y] of the admittance is 0 (zero). As shown in FIG. 11 , the real part Re[Y] of the admittance at frequency f1 is smaller in the terahertz device 10 shown in FIG. 9 than in the terahertz device 10X shown in FIG. 10 . In other words, the circular pad electrodes 171 and 172 shown in FIG. 9 , i.e., including curved portions, can suppress reflection better than the rectangular pad electrodes 171X and 172X shown in FIG. 10 . Furthermore, compared to the terahertz device 10X shown in FIG. 10 , the terahertz device 10 shown in FIG. 9 can lower the Q value at frequencies other than the target frequency. In other words, the curved portions of the pad electrodes 171 and 172 are curved to lower the Q value at frequencies other than the target frequency.

[0083] Therefore, the terahertz device 10 of the first embodiment including the first pad electrode 171 having a circular shape in a planar view suppresses the generation of electromagnetic waves having a frequency different from that of electromagnetic waves having a desired frequency, compared to the terahertz device 10X of the comparative example. Similarly, the terahertz device 10 of the first embodiment including the second pad electrode 172 having a circular shape in a planar view suppresses the generation of electromagnetic waves having a frequency different from that of electromagnetic waves having a desired frequency, compared to the terahertz device 10X of the comparative example.

[0084] The first electrode plate 183 and the second electrode plate 184 of the first capacitor 181 include curved portions 230 at their corners. Therefore, the terahertz device 10 of the first embodiment including the first capacitor 181 suppresses the generation of electromagnetic waves of frequencies different from the desired frequency compared to the comparative terahertz device 10X including the rectangular first capacitor 181X. The first electrode plate 183 and the second electrode plate 184 of the second capacitor 182 include curved portions 230 at their corners. Therefore, the terahertz device 10 of the first embodiment including the second capacitor 182 suppresses the generation of electromagnetic waves of frequencies different from the desired frequency compared to the comparative terahertz device 10X including the rectangular second capacitor 182X.

[0085] (Effects of First Embodiment) The terahertz device 10 of the first embodiment has the following effects: (1-1) The terahertz device 10 includes a substrate 100 including a substrate surface 101, an active element 130 provided on the substrate surface 101 and configured to oscillate or detect electromagnetic waves, an antenna 150 electrically connected to the active element 130, and a circuit member 160 provided on the substrate surface 101 and electrically connected to the antenna 150, and the circuit member 160 includes a curved portion 230 that is curved in a planar view when viewed from a Z-axis direction perpendicular to the substrate surface 101.

[0086] The terahertz device 10 can alleviate electric field concentration on the circuit member 160 by using the curved portion 230. The terahertz device 10 can also reduce reflection of electromagnetic waves by using the curved portion 230. Therefore, the terahertz device 10 can suppress the generation of electromagnetic waves with frequencies different from electromagnetic waves with a desired frequency.

[0087] (1-2) The circuit member 160 includes a first pad electrode 171 and a second pad electrode 172 electrically connected to the antenna 150. The first pad electrode 171 has a circular shape in a plan view. The first pad electrode 171 is curved around the entire circumference of the first pad electrode 171. This first pad electrode 171 can be said to include a curved portion 230. This first pad electrode 171 reflects electromagnetic waves less than a rectangular first pad electrode 171X that includes right-angled corners. Therefore, the terahertz device 10 can suppress the generation of electromagnetic waves with frequencies different from those of the desired frequency.

[0088] (1-3) The circuit member 160 includes a first pad electrode 171 and a second pad electrode 172 electrically connected to the antenna 150. The second pad electrode 172 has a circular shape in a plan view. The second pad electrode 172 is curved around the entire circumference of the second pad electrode 172. This second pad electrode 172 can be said to include a curved portion 230. This second pad electrode 172 reflects electromagnetic waves less than a rectangular second pad electrode 172X that includes right-angled corners. Therefore, the terahertz device 10 can suppress the generation of electromagnetic waves with frequencies different from those of the desired frequency.

[0089] (1-4) The corners of the first electrode plate 183 and the second electrode plate 184 of the first capacitor 181 include curved portions 230. Therefore, the terahertz device 10 of the first embodiment including the first capacitor 181 can suppress the generation of electromagnetic waves with frequencies different from those of the desired frequency, compared to the terahertz device 10X of the comparative example including the rectangular first capacitor 181X.

[0090] (1-5) The corners of the first electrode plate 183 and the second electrode plate 184 of the second capacitor 182 include curved portions 230. Therefore, the terahertz device 10 of the first embodiment including the second capacitor 182 can suppress the generation of electromagnetic waves with frequencies different from those of the desired frequency, compared to the terahertz device 10X of the comparative example including the rectangular second capacitor 182X.

[0091] (Modifications of the First Embodiment) The first embodiment can be modified, for example, as follows. The first embodiment and the following modifications can be combined with each other as long as no technical contradiction occurs. In the following modifications, parts that are common to the first embodiment are assigned the same reference numerals as in the first embodiment, and descriptions thereof will be omitted.

[0092] 21 , a circuit member 160A of a modified terahertz device 10A includes a first pad electrode 171A and a second pad electrode 172A. The first pad electrode 171A has a rectangular shape with rounded corners. The first pad electrode 171A has a rectangular shape in a plan view. The first pad electrode 171A has a rectangular shape including four corner portions 261 to 264. The first pad electrode 171A includes curved portions 230. The curved portions 230 are provided at the four corner portions 261 to 264, respectively.

[0093] The first pad electrode 171A includes a first corner portion 261 and a second corner portion 262 that is located closer to the active element 130 than the first corner portion 261. The first pad electrode 171A also includes a third corner portion 263 that is located diagonally opposite the first corner portion 261, and a fourth corner portion 264 that is located diagonally opposite the second corner portion 262. A curved portion 230 is provided in each of the first to fourth corner portions 261 to 264.

[0094] The second pad electrode 172A has a rectangular shape with rounded corners. The second pad electrode 172A has a rectangular shape in a plan view. The second pad electrode 172A has a rectangular shape including four corner portions 261 to 264. The second pad electrode 172A includes curved portions 230. The curved portions 230 are provided at the four corner portions 261 to 264, respectively.

[0095] The second pad electrode 172A includes a first corner portion 261 and a second corner portion 262 that is located closer to the active element 130 than the first corner portion 261. The second pad electrode 172A also includes a third corner portion 263 that is located diagonally opposite the first corner portion 261, and a fourth corner portion 264 that is located diagonally opposite the second corner portion 262. A curved portion 230 is provided in each of the first to fourth corner portions 261 to 264.

[0096] In the first pad electrode 171A, the curved portion 230 may be provided in at least one of the first to fourth corner portions 261 to 264. In the second pad electrode 172A, the curved portion 230 may be provided in at least one of the first to fourth corner portions 261 to 264.

[0097] 22 , a circuit member 160B of a modified terahertz device 10B includes a first pad electrode 171B and a second pad electrode 172B. The curved portions 230 may be provided at a second corner portion 262 and a fourth corner portion 264 of the first pad electrode 171B and the second pad electrode 172B. In this terahertz device 10B, it can be said that the first pad electrode 171B and the second pad electrode 172B have the same shape in a plan view.

[0098] 23 , a circuit member 160C of a modified terahertz device 10C includes a first pad electrode 171C and a second pad electrode 172C. Curved portions 230 are provided at a second corner portion 262 and a fourth corner portion 264 of the first pad electrode 171C. Curved portions 230 are also provided at a first corner portion 261 and a third corner portion 263 of the second pad electrode 172C. In this terahertz device 10C, the first pad electrode 171C and the second pad electrode 172C can be said to have symmetrical shapes with respect to the antenna 150 in a plan view.

[0099] 24 , a circuit member 160D of a modified terahertz device 10D includes a first pad electrode 171D and a second pad electrode 172D. The curved portions 230 may be provided at second corner portions 262 and third corner portions 263 of the first pad electrode 171D and the second pad electrode 172D. In this terahertz device 10D, the first pad electrode 171D and the second pad electrode 172D can be said to have symmetrical shapes with respect to the antenna 150 in a plan view.

[0100] As shown in FIG. 25 , a circuit member 160E of a modified terahertz device 10E includes a first pad electrode 171E and a second pad electrode 172E. The curved portion 230 is formed around at least half of the circumference of the first pad electrode 171E and the second pad electrode 172E. In the first pad electrode 171E and the second pad electrode 172E, the curved portion 230 can be considered to be provided at a second corner portion 262 and a third corner portion 263. The first pad electrode 171E and the second pad electrode 172E can be considered to include a semicircular portion 231 in a plan view. The curved portion 230 may be provided at adjacent corner portions. For example, the curved portion 230 may be provided at the first corner portion 261 and the second corner portion 262. Alternatively, the curved portion 230 may be provided at the first corner portion 261 and the fourth corner portion 264. The curved portion 230 may also be provided at the third corner portion 263 and the fourth corner portion 264 .

[0101] The curved portion 230 may be provided at three of the first to fourth corner portions 261 to 264. Alternatively, the curved portion 230 may be provided at one of the first to fourth corner portions 261 to 264.

[0102] 26 , a circuit member 160F of a modified terahertz device 10F includes a first pad electrode 171 and a second pad electrode 172. The first pad electrode 171 and the second pad electrode 172 are provided at corners of the substrate 100.

[0103] The first pad electrode is disposed at the first corner 111. The second pad electrode 172 is disposed at the third corner 113. The third corner 113 is located at a diagonal corner of the substrate 100 with respect to the first corner 111. It can be said that the first pad electrode and the second pad electrode 172 are disposed at two diagonally opposite corners of the substrate 100.

[0104] The circuit member 160F includes a first wiring member 200F that electrically connects the first pad electrode 171 and the first antenna member 151, and a second wiring member 210F that electrically connects the second pad electrode 172 and the second antenna member 152.

[0105] The first wiring member 200F includes a first wiring portion 201F that electrically connects the first pad electrode 171 and the first capacitor 181. The first wiring portion 201F includes a first wiring 205, a second wiring 206, and a curved portion 207. The first wiring 205 is electrically connected to the first pad electrode 171 and extends from the first pad electrode 171 in the X-axis direction toward the substrate side surface 106. The second wiring 206 is electrically connected to the first capacitor 181 and extends from the first capacitor 181 in the Y-axis direction toward the substrate side surface 103. The curved portion 207 is curved so as to electrically connect the first wiring 205 extending in the X-axis direction with the second wiring 206 extending in the Y-axis direction.

[0106] In one example, the first wiring 205, the second wiring 206, and the curved portion 207 may have the same width W41. The width W41 of the first wiring 205, the second wiring 206, and the curved portion 207 is smaller than the width W11 of the first pad electrode 171. The first wiring 205 and the second wiring 206 may have different widths.

[0107] The first wiring member 200F includes a curved portion 207. This allows electric field concentration in the first wiring member 200F to be alleviated compared to when the first wiring 205 and the second wiring 206 are connected at a right angle. The curved portion 207 allows the terahertz device 10F to reduce reflection of electromagnetic waves. This allows the terahertz device 10F to suppress the generation of electromagnetic waves with frequencies different from those of the desired frequency.

[0108] The second wiring member 210F includes a first wiring portion 211F that electrically connects the second pad electrode 172 and the second capacitor 182. The first wiring portion 211F includes a first wiring 215, a second wiring 216, and a curved portion 217. The first wiring 215 is electrically connected to the second pad electrode 172 and extends from the second pad electrode 172 in the X-axis direction toward the substrate side surface 104. The second wiring 216 is electrically connected to the second capacitor 182 and extends from the second capacitor 182 in the Y-axis direction toward the substrate side surface 105. The curved portion 217 is curved so as to electrically connect the first wiring 215 extending in the X-axis direction with the second wiring 216 extending in the Y-axis direction.

[0109] In one example, the first wiring 215, the second wiring 216, and the curved portion 217 may have the same width W42. The width W42 of the first wiring 215, the second wiring 216, and the curved portion 217 is smaller than the width W12 of the second pad electrode 172. The first wiring 215 and the second wiring 216 may have different widths.

[0110] The second wiring member 210F includes a curved portion 217. This allows electric field concentration in the second wiring member 210F to be alleviated compared to when the first wiring 215 and the second wiring 216 are connected at a right angle. The curved portion 217 allows the terahertz device 10F to reduce reflection of electromagnetic waves. This allows the terahertz device 10F to suppress the generation of electromagnetic waves with frequencies different from those of the desired frequency.

[0111] 26, the second pad electrode 172 may be arranged at a second corner 112 formed by the substrate side surface 104 and the substrate side surface 105 on the substrate surface 101 of the substrate 100. Although not shown, the first pad electrode 171 may be arranged at a fourth corner 114 in FIG. 26. Furthermore, the second pad electrode 172 may be arranged at the second corner 112, and the first pad electrode 171 may be arranged at the fourth corner 114 diagonally opposite the second corner 112.

[0112] 27 , the circuit member 160G of the terahertz device 10G may include fillet portions 208, 218 in comparison with the terahertz device 10F shown in FIG. 26 . The fillet portion 208 is provided between the first pad electrode 171 and the first wiring portion 201F (first wiring 205). The fillet portion 208 has a shape that widens from the first wiring portion 201F toward the first pad electrode 171. The fillet portion 208 acts as a curved portion between the first wiring portion 201F and the first pad electrode 171. Therefore, the terahertz device 10G can further mitigate electric field concentration and further reduce electromagnetic wave reflection compared to a device that does not include the fillet portion 208.

[0113] The fillet portion 218 is provided between the second pad electrode 172 and the first wiring portion 211F (first wiring 215). The fillet portion 218 has a shape that becomes wider from the first wiring portion 211F toward the second pad electrode 172. The fillet portion 218 acts as a curved portion between the first wiring portion 211F and the second pad electrode 172. Therefore, the terahertz device 10G can further alleviate electric field concentration compared to a device that does not include the fillet portion 218, thereby further reducing reflection of electromagnetic waves.

[0114] Second Embodiment A terahertz device 20 according to a second embodiment will be described with reference to Fig. 28. Note that in the terahertz device 20 according to the second embodiment, components similar to those in the terahertz device 10 according to the first embodiment are denoted by the same reference numerals. Below, a description of the components similar to those in the first embodiment will be omitted, and only components different from those in the first embodiment will be described.

[0115] 28 is a schematic plan view of an exemplary terahertz device 20 according to the second embodiment. The terahertz device 20 of the second embodiment includes an active element 130, an antenna 150, and a circuit member 300 electrically connected to the antenna 150. The circuit member 300 is disposed between the antenna 150 and a substrate side surface 103 of the substrate 100. In the terahertz device 20 of the second embodiment, it can be said that the circuit member 300 is disposed biased toward one substrate side surface 103 of the substrate 100 relative to the antenna 150.

[0116] The circuit member 300 includes a first pad electrode 171 and a second pad electrode 172. The first pad electrode 171 and the second pad electrode 172 are arranged along the substrate side surface 103 of the substrate 100. In other words, the first pad electrode 171 and the second pad electrode 172 are arranged offset to one side in the Y-axis direction with respect to the antenna 150 extending in the X-axis direction. The first pad electrode 171 is arranged at a first corner 111 defined by the substrate side surfaces 103 and 104. The second pad electrode 172 is arranged at a fourth corner 114 defined by the substrate side surfaces 103 and 106.

[0117] The first pad electrode 171 has a circular shape in a plan view. It can be said that the first pad electrode 171 includes a curved portion over the entire end portion. The second pad electrode 172 has a circular shape in a plan view. It can be said that the second pad electrode 172 includes a curved portion over the entire end portion.

[0118] The circuit member 300 includes one capacitor 181 disposed between the first pad electrode 171, the second pad electrode 172, and the antenna 150. The capacitor 181 includes a first electrode plate 183 and a second electrode plate 184. The first electrode plate 183 and the second electrode plate 184 may have the same shape as each other in a plan view. In FIG. 28 , the second electrode plate 184 is depicted smaller than the first electrode plate 183 to illustrate the second electrode plate 184. In one example, the first electrode plate 183 and the second electrode plate 184 may have a rectangular shape in which the length in the Y-axis direction is greater than the length in the X-axis direction. The first electrode plate 183 and the second electrode plate 184 face each other with the insulating layer 120 sandwiched therebetween.

[0119] The circuit member 300 includes a first wiring member 310 that electrically connects the first pad electrode 171 and the first antenna member 151, and a second wiring member 320 that electrically connects the second pad electrode 172 and the second antenna member 152. The capacitor 181 is electrically connected between the first wiring member 310 and the second wiring member 320.

[0120] The first wiring member 310 includes a first wiring portion 311 that electrically connects the first pad electrode 171 and the first electrode plate 183 of the capacitor 181, and a second wiring portion 312 that electrically connects the capacitor 181 and the first antenna member 151.

[0121] The first wiring portion 311 includes a first wiring 313, a second wiring 314, and a curved portion 315. The first wiring 313 is electrically connected to the first pad electrode 171 and extends in the X-axis direction from the first pad electrode 171 toward the second pad electrode 172. The second wiring 314 is electrically connected to the capacitor 181 and extends in the Y-axis direction from the capacitor 181 toward the substrate side surface 103. The curved portion 315 is curved to electrically connect the first wiring 313 extending in the X-axis direction with the second wiring 314 extending in the Y-axis direction. In one example, the first wiring 313, the second wiring 314, and the curved portion 315 may have the same width W51. The width W51 of the first wiring 313, the second wiring 314, and the curved portion 315 is smaller than the width W11 of the first pad electrode 171.

[0122] The second wiring member 320 includes a first wiring portion 321 that electrically connects the second pad electrode 172 and the second electrode plate 184 of the capacitor 181, and a second wiring portion 322 that electrically connects the capacitor 181 and the second antenna member 152.

[0123] The second wiring member 320 includes a first wiring portion 321 that electrically connects the second pad electrode 172 and the capacitor 181. The first wiring portion 321 includes a first wiring 323, a second wiring 324, and a curved portion 325. The first wiring 323 is electrically connected to the second pad electrode 172 and extends in the X-axis direction from the second pad electrode 172 toward the first pad electrode 171. The second wiring 324 is electrically connected to the capacitor 181 and extends in the Y-axis direction from the capacitor 181 toward the substrate side surface 103. The curved portion 325 is curved so as to electrically connect the first wiring 323 extending in the X-axis direction and the second wiring 324 extending in the Y-axis direction. In one example, the first wiring 323, the second wiring 324, and the curved portion 325 may have the same width W52. The width W52 of the first wiring 323, the second wiring 324, and the curved portion 325 is smaller than the width W12 of the second pad electrode 172.

[0124] The circuit member 300 includes one resistive element 221 disposed between the first pad electrode 171 and the second pad electrode 172 and the capacitor 181. The resistive element 221 is electrically connected between the first wiring member 310 and the second wiring member 320. In particular, the resistive element 221 is electrically connected between the second wiring 314 of the first wiring member 310 and the second wiring 324 of the second wiring member 320.

[0125] (Effects of Second Embodiment) According to the terahertz device 20 of the second embodiment, in addition to the effects of the terahertz device 10 of the first embodiment, the following effects are achieved.

[0126] (2-1) The terahertz device 20 includes a first pad electrode 171 and a second pad electrode 172. The first pad electrode 171 and the second pad electrode 172 are arranged along the substrate side surface 103 of the substrate 100. Wires or the like are connected to the first pad electrode 171 and the second pad electrode 172 for applying a voltage from the outside or transmitting a detected signal to the outside. In this terahertz device 20, wires or the like can be connected to the first pad electrode 171 and the second pad electrode 172 from both sides in the X-axis direction. Furthermore, in this terahertz device 20, wires or the like can be connected to the first pad electrode 171 and the second pad electrode 172 from one side in the Y-axis direction. In this way, the degree of freedom in the connection direction to the first pad electrode 171 and the second pad electrode 172 can be increased. Furthermore, the degree of freedom in the arrangement and orientation of the terahertz device 20 can also be increased.

[0127] (Modifications of the Second Embodiment) The second embodiment can be modified, for example, as follows. The second embodiment can be combined with the following modifications as long as no technical contradiction occurs. In the following modifications, parts common to the second embodiment are designated by the same reference numerals as in the second embodiment, and their description will be omitted.

[0128] 29 , a circuit member 300A of a modified terahertz device 20A includes a first pad electrode 171A and a second pad electrode 172A. The first pad electrode 171A has a rectangular shape with rounded corners in a plan view. The second pad electrode 172A has a rectangular shape with rounded corners. Similar to the terahertz device 20 of the second embodiment, the modified terahertz device 20A can suppress the generation of electromagnetic waves with frequencies different from those of a desired frequency.

[0129] 30 , a circuit member 300B of a modified terahertz device 20B includes fillet portions 316, 326. The fillet portion 316 is provided between the first pad electrode 171 and the first wiring portion 311 (first wiring 313). The fillet portion 316 has a shape that becomes wider from the first wiring portion 311 toward the first pad electrode 171. This fillet portion 316 acts as a curved portion between the first wiring portion 311 and the first pad electrode 171. Therefore, this terahertz device 20B can further alleviate electric field concentration compared to a device that does not include the fillet portion 316, thereby further reducing reflection of electromagnetic waves.

[0130] The fillet portion 326 is provided between the second pad electrode 172 and the first wiring portion 321 (first wiring 323). The fillet portion 326 has a shape that becomes wider from the first wiring portion 321 toward the second pad electrode 172. The fillet portion 326 acts as a curved portion between the first wiring portion 321 and the second pad electrode 172. Therefore, the terahertz device 20B can further alleviate electric field concentration compared to a device that does not include the fillet portion 326, and can further reduce reflection of electromagnetic waves.

[0131] Third Embodiment A terahertz device 30 according to a third embodiment will be described with reference to Fig. 31. Note that, in the terahertz device 30 according to the third embodiment, components similar to those of the terahertz devices 10 and 20 according to the first and second embodiments are denoted by the same reference numerals. In the following, a description of the components similar to those of the first and second embodiments will be omitted, and only components different from those of the first and second embodiments will be described.

[0132] 31 is a schematic plan view of an exemplary terahertz device 30 according to the third embodiment. The terahertz device 30 of the third embodiment differs from the terahertz device 10 of the first embodiment shown in FIG. 2 mainly in that it includes a plurality of dummy pad electrodes 330.

[0133] The multiple dummy pad electrodes 330 are arranged at the corners 111 to 114 of the substrate 100. The first pad electrode 171 is arranged closer to the substrate side surface 103 of the substrate 100. The first pad electrode 171 is arranged at the center of the substrate surface 101 in the X-axis direction. The first pad electrode 171 is arranged between the first corner 111 and the fourth corner 114 in the X-axis direction. The second pad electrode 172 is arranged closer to the substrate side surface 105 of the substrate 100. The second pad electrode 172 is arranged at the center of the substrate surface 101 in the X-axis direction. The second pad electrode 172 is arranged between the second corner 112 and the third corner 113 in the X-axis direction.

[0134] The plurality of dummy pad electrodes 330 are arranged at the four corners 111 to 114 of the substrate 100. As described above, the first pad electrode 171 is arranged between the first corner 111 and the fourth corner 114, and the second pad electrode 172 is arranged between the second corner 112 and the third corner 113. In other words, the first pad electrode 171 and the second pad electrode 172 are not arranged at the first to fourth corners 111 to 114. It can be said that the plurality of dummy pad electrodes 330 are arranged at the corners 111 to 114 of the substrate 100 where the first pad electrode 171 and the second pad electrode 172 are not arranged.

[0135] In one example, the multiple dummy pad electrodes 330 have a circular shape in a plan view. The multiple dummy pad electrodes 330 are curved around the entire circumference. It can be said that the multiple dummy pad electrodes 330 include the curved portion 230 over the entire end portion. The multiple dummy pad electrodes 330 may have a shape that includes the curved portion 230 in at least a part of the end portion.

[0136] The first pad electrode 171 and the second pad electrode 172 are provided with bumps 331. Similarly, the plurality of dummy pad electrodes 330 are provided with bumps 331. The bumps 331 may be configured with a layered structure of, for example, a metal layer containing Cu, a metal layer containing Ti, and a metal layer containing tin (Sn). The bumps 331 may also have a single-layer structure. The bumps 331 may also be omitted.

[0137] (Operation of Third Embodiment) FIG. 32 shows a schematic cross section of a terahertz unit 900 in which the terahertz device 30 of the third embodiment is mounted.

[0138] The terahertz unit 900 includes the terahertz device 30, a dielectric 910, an antenna base 920, a reflective film 930 as a reflector, and a gas space 940. The gas in the gas space 940 is, for example, air.

[0139] The dielectric 910 is made of a dielectric material that transmits electromagnetic waves generated by the terahertz device 30. In one example, the dielectric 910 is made of a resin material. An example of the resin material is epoxy resin (e.g., glass epoxy resin). The dielectric 910 has insulating properties. The dielectric refractive index n2, which is the refractive index (absolute refractive index) of the dielectric 910, is lower than the element refractive index n1, which is the refractive index of the terahertz device 30. The element refractive index n1 is higher than the gas refractive index n3, which is the refractive index of the gas in the gas space 940. The dielectric refractive index n2 is higher than the gas refractive index n3. For example, the dielectric refractive index n2 is 1.55, and the element refractive index n1 is 3.4. The element refractive index n1 is the refractive index of the substrate 100. In one example, the substrate 100 is made of a material containing InP.

[0140] The dielectric 910 surrounds the terahertz device 30. In one example, the dielectric 910 surrounds the entire terahertz device 30. It can also be said that the dielectric 910 seals the terahertz device 30. The dielectric 910 has, for example, a rectangular plate shape.

[0141] The antenna base 920 has a rectangular parallelepiped shape as a whole. The antenna base 920 is made of, for example, an insulating material. In one example, the antenna base 920 is made of a dielectric material, such as a synthetic resin such as epoxy resin. The material that makes up the antenna base 920 is arbitrary, and may be, for example, silicon or glass.

[0142] A dielectric 910 is laminated on a base surface 921 of the antenna base 920. The dielectric 910 is provided so as to protrude from the antenna base 920 when viewed from the Z-axis direction. The antenna base 920 includes an antenna recess 922 recessed from the base surface 921. The antenna recess 922 is recessed in a direction away from the base surface 921 and away from the dielectric 910. In one example, the antenna recess 922 has an overall hemispherical shape. The antenna recess 922 opens toward the dielectric 910. The opening of the antenna recess 922 is circular when viewed from the Z-axis direction.

[0143] The antenna recess 922 has an antenna surface 923 that faces the terahertz device 30 across the dielectric 910 and the gas space 940. The antenna surface 923 is the inner surface of the antenna recess 922. The antenna surface 923 has a shape corresponding to the antenna shape. In one example, the antenna surface 923 is curved so as to be concave in a direction away from the terahertz device 30. The antenna surface 923 is curved, for example, in a cone shape. In one example, the antenna surface 923 is curved so as to have a parabolic antenna shape.

[0144] The reflective film 930 reflects the electromagnetic waves emitted from the terahertz device 30 in one direction. The reflective film 930 is disposed on the antenna surface 923. Therefore, the reflective film 930 has an antenna shape. In one example, the reflective film 930 is a parabolic mirror of revolution. The reflective film 930 is made of a material that reflects the electromagnetic waves emitted from the terahertz device 30, and is made of, for example, a metal such as Cu or an alloy. The reflective film 930 may have a single-layer structure or a multi-layer structure. The electromagnetic waves emitted from the terahertz device 30 are reflected upward by the reflective film 930. Therefore, the terahertz unit 900 is configured to emit electromagnetic waves upward.

[0145] The terahertz unit 900 includes external electrodes 951 and 952 used for electrical connection to the outside, and conductive portions 961 and 962 electrically connected to the terahertz device 30. The external electrodes 951 and 952 and the conductive portions 961 and 962 are each provided on a dielectric 910. The external electrodes 951 and 952 are provided so as to be exposed from the dielectric 910. The conductive portions 961 and 962 are provided within the dielectric 910.

[0146] The external electrodes 951 and 952 are disposed at positions that do not overlap the reflective film 930 when viewed from the Z-axis direction. Specifically, the external electrodes 951 and 952 are provided on a portion of the dielectric 910 that protrudes beyond the antenna base 920.

[0147] The conductive portions 961 and 962 connect the external electrodes 951 and 952 to the terahertz device 30. More specifically, the conductive portion 961 electrically connects the external electrode 951 to the first pad electrode 171 of the terahertz device 30. The conductive portion 962 electrically connects the external electrode 952 to the second pad electrode 172 of the terahertz device 30.

[0148] The terahertz device 30 is flip-chip mounted on the conductive portions 961 and 962. Specifically, the terahertz device 30 is disposed with the substrate surface 101 of the substrate 100 facing the conductive portions 961 and 962. The first pad electrode 171 is connected to the conductive portion 961 by a bump 331. The second pad electrode 172 is connected to the conductive portion 962 by a bump 331.

[0149] Although not shown, the terahertz unit 900 includes a plurality of dummy conductive portions arranged on the same plane as the conductive portions 961 and 962. The plurality of dummy conductive portions are arranged at positions corresponding to the dummy pad electrode 330 shown in FIG. 31 . The plurality of dummy conductive portions may be connected to either the conductive portion 961 or 962. The dummy pad electrode 330 shown in FIG. 31 is connected to the dummy conductive portion by a bump 331.

[0150] The terahertz device 30 of the third embodiment includes a first pad electrode 171 and a second pad electrode 172 used to apply a voltage to the active element 130 or to transmit a signal detected by the active element 130. The first pad electrode 171 and the second pad electrode 172 are electrically connected to the conductive portions 961 and 962 by bumps 331. Therefore, the length of the transmission path of the signal or the like can be shortened compared to when a wire or the like is connected to the first pad electrode 171 and the second pad electrode 172. Furthermore, the inductance in the transmission path can be reduced.

[0151] The terahertz device 30 of the third embodiment can be mounted on the support substrate 810 of the terahertz unit 800, similar to the terahertz device 10 of the first embodiment. The terahertz device 30 of the third embodiment can also be applied to the terahertz unit 900. In this way, the terahertz device 30 can be used in various terahertz units.

[0152] The terahertz device 30 includes a plurality of dummy pad electrodes 330. The plurality of dummy pad electrodes 330 are arranged at four corners 111 to 114 of the substrate 100. The plurality of dummy pad electrodes 330 are connected to dummy conductive portions by bumps 331. This makes it possible to prevent the substrate 100 of the terahertz device 30 from tilting with respect to the direction in which electromagnetic waves are emitted or incident, such as the antenna surface 923.

[0153] The terahertz device 30 is mounted by the first pad electrode 171, the second pad electrode 172, and a plurality of dummy pad electrodes 330. Therefore, compared to a device that does not include the dummy pad electrodes 330, the connection to the mounting object can be made stronger.

[0154] The stress on the terahertz device 30 is applied to the first pad electrode 171, the second pad electrode 172, and the plurality of dummy pad electrodes 330. Therefore, the dummy pad electrode 330 can relieve the stress on the first pad electrode 171 and the second pad electrode 172.

[0155] (Effects of Third Embodiment) According to the terahertz device 30 of the third embodiment, in addition to the effects of the terahertz device 10 of the first embodiment, the following effects are achieved.

[0156] (3-1) The terahertz device 30 of the third embodiment includes a first pad electrode 171 and a second pad electrode 172 used to apply a voltage to the active element 130 or to transmit a signal detected by the active element 130. The first pad electrode 171 and the second pad electrode 172 are electrically connected to the conductive portions 961 and 962 by bumps 331. Therefore, the length of the transmission path of the signal or the like can be shortened compared to when a wire or the like is connected to the first pad electrode 171 and the second pad electrode 172. Furthermore, the inductance in the transmission path can be reduced.

[0157] (3-2) The terahertz device 30 of the third embodiment can be mounted on the support substrate 810 of the terahertz unit 800, similar to the terahertz device 10 of the first embodiment. Furthermore, the terahertz device 30 of the third embodiment can be applied to the terahertz unit 900. In this way, the terahertz device 30 can be used in various terahertz units.

[0158] (3-3) The terahertz device 30 includes a plurality of dummy pad electrodes 330. The plurality of dummy pad electrodes 330 are arranged at the four corners 111 to 114 of the substrate 100. The plurality of dummy pad electrodes 330 are connected to dummy conductive portions by bumps 331. This makes it possible to prevent the substrate 100 of the terahertz device 30 from tilting with respect to the direction in which electromagnetic waves are emitted or incident, such as the antenna surface 923.

[0159] (3-4) The terahertz device 30 is mounted using the first pad electrode 171, the second pad electrode 172, and a plurality of dummy pad electrodes 330. Therefore, compared to a device that does not include the dummy pad electrodes 330, the connection to the mounting object can be made stronger.

[0160] (3-5) Stress on the terahertz device 30 is applied to the first pad electrode 171, the second pad electrode 172, and the plurality of dummy pad electrodes 330. Therefore, the dummy pad electrode 330 can relieve stress on the first pad electrode 171 and the second pad electrode 172.

[0161] (3-6) In one example, the multiple dummy pad electrodes 330 have a circular shape in a planar view. The multiple dummy pad electrodes 330 are curved around the entire circumference. It can be said that the multiple dummy pad electrodes 330 include the curved portion 230 over the entire end portion. Therefore, reflection of electromagnetic waves by the multiple dummy pad electrodes 330 is suppressed. As a result, the terahertz device 30 can suppress the generation of electromagnetic waves with frequencies different from electromagnetic waves with a desired frequency.

[0162] (Modifications of the Third Embodiment) The third embodiment can be modified, for example, as follows. The third embodiment can be combined with the following modifications as long as no technical contradiction occurs. In the following modifications, parts common to the third embodiment are designated by the same reference numerals as in the third embodiment, and descriptions thereof will be omitted.

[0163] 33, a terahertz device 30A of the modified example differs from the terahertz device 10F shown in Fig. 26 in that it includes a plurality of dummy pad electrodes 330. The first pad electrode 171 is disposed at a first corner 111 of the substrate 100, and the second pad electrode 172 is disposed at a third corner 113 of the substrate 100. The dummy pad electrodes 330 are disposed at the second corner 112 and the fourth corner 114 of the substrate 100 where the first pad electrode 171 and the second pad electrode 172 are not disposed. This terahertz device 30A achieves the same effects as the terahertz device 30 of the third embodiment.

[0164] 34, a terahertz device 30B of a modified example differs from the terahertz device 20 shown in Fig. 28 in that it includes a plurality of dummy pad electrodes 330. The first pad electrode 171 is disposed at a first corner 111 of the substrate 100, and the second pad electrode 172 is disposed at a fourth corner 114 of the substrate 100. The dummy pad electrodes 330 are disposed at the second corner 112 and the third corner 113 of the substrate 100 where the first pad electrode 171 and the second pad electrode 172 are not disposed. This terahertz device 30B achieves the same effects as the terahertz device 30 of the third embodiment.

[0165] 35 to 43, a terahertz device 40 according to a fourth embodiment will be described. Note that, in the terahertz device 40 according to the fourth embodiment, the same components as those in the terahertz devices 10, 20, and 30 according to the first, second, and third embodiments are denoted by the same reference numerals.

[0166] (Schematic configuration of terahertz device) Fig. 35 is a schematic perspective view of an exemplary terahertz device 40 according to the fourth embodiment. Fig. 36 is a schematic plan view of the terahertz device of Fig. 35. Fig. 37 is a schematic plan view showing some components of the terahertz device 40 of Fig. 36, illustrating the arrangement of the first antenna member 410, the second antenna member 420, the first active element 450, the second active element 460, the first resistor element 501, and the second resistor element 502. Fig. 38 is a schematic cross-sectional view taken along line F38-F38 in Fig. 36.

[0167] As shown in Figures 35 to 38, the terahertz device 40 includes a substrate 100. The substrate 100 has a flat plate shape. As shown in Figure 35, the substrate 100 has a rectangular parallelepiped shape. In one example, the shape of the substrate 100 is a square in a plan view. Note that the shape of the substrate 100 in a plan view is not limited to a rectangular shape, and may be a circular shape, an elliptical shape, or a polygonal shape.

[0168] The substrate 100 includes a substrate front surface 101 and a substrate back surface 102 opposite the substrate front surface 101. The substrate 100 includes a plurality of substrate side surfaces 103, 104, 105, and 106 connecting the substrate front surface 101 and the substrate back surface 102. The substrate side surfaces 103 to 106 face either the X-axis direction or the Y-axis direction. The substrate side surfaces 103 and 105 extend along the XZ plane. The substrate side surfaces 103 and 105 constitute both end surfaces in the Y-axis direction. The substrate side surfaces 104 and 106 extend along the YZ plane. The substrate side surfaces 104 and 106 constitute both end surfaces in the X-axis direction.

[0169] In a plan view, the substrate surface 101 of the substrate 100 has a rectangular shape including four corners 111, 112, 113, and 114. The first corner 111 is formed by the substrate side surface 103 and the substrate side surface 104. The second corner 112 is formed by the substrate side surface 104 and the substrate side surface 105. The third corner 113 is formed by the substrate side surface 105 and the substrate side surface 106. The fourth corner 114 is formed by the substrate side surface 106 and the substrate side surface 103.

[0170] The substrate 100 is made of at least one semiconductor material selected from the group consisting of InP (indium phosphide), GaAs (gallium arsenide), AlGaAs (aluminum gallium arsenide), InGaAs (indium gallium arsenide), InGaAsP (indium gallium arsenide phosphide), Si (silicon), SiC (silicon carbide), GaN (gallium nitride), and single crystal AlN (aluminum nitride). In one example, the substrate 100 is made of a material including InP.

[0171] The substrate 100 has a length Bx in the X-axis direction and a length By in the Y-axis direction. The length Bx in the X-axis direction can be 1 mm or less. In one example, the length Bx in the X-axis direction can be 500 μm. The length By in the Y-axis direction can be 1 mm or less. In one example, the length By in the Y-axis direction can be 500 μm.

[0172] The terahertz device 40 includes an insulating layer 120 provided on a substrate 100. The insulating layer 120 may cover a portion of the substrate surface 101 of the substrate 100. In one example, the insulating layer 120 may cover a central portion of the substrate surface 101. The insulating layer 120 may be disposed in the central portion of the substrate surface 101 in the X-axis direction and the Y-axis direction. The insulating layer 120 may cover a region of the substrate surface 101 where the conductive layer 400 constituting the slot antenna 402 is disposed. The insulating layer 120 may cover the entire substrate surface 101. The insulating layer 120 is made of an insulating material. The insulating layer 120 is made of a material containing, for example, SiO2.

[0173] The terahertz device 40 includes a conductive layer 400 disposed on the substrate surface 101 of the substrate 100. The conductive layer 400 is disposed on a portion of the substrate surface 101 of the substrate 100. The conductive layer 400 is made of at least one metal material selected from the group consisting of gold (Au), silver (Ag), aluminum (Al), copper (Cu), titanium (Ti), titanium nitride (TiN), and platinum (Pt). It can also be said that the conductive layer 400 includes at least one of Au, Ag, Al, Cu, Ti, and Pt. In one example, the conductive layer 400 is made of a material containing Au. The conductive layer 400 may also be made of a stacked structure of multiple metal layers.

[0174] The terahertz device 40 includes a slot 401 arranged in a conductive layer 400. The slot 401 has an annular shape in a plan view. In one example, the slot 401 has a circular annular shape in a plan view. Therefore, the terahertz device 40 includes the slot 401 having a circular annular shape.

[0175] The conductive layer 400 includes a first antenna member 410 defined by a slot 401 and a second antenna member 420 disposed to surround the first antenna member 410 via the slot 401. In one example, the first antenna member 410 has a circular shape in a plan view. In one example, the first antenna member 410 is disposed at the center of the substrate 100 in a plan view. In one example, the second antenna member 420 has a rectangular shape. In a plan view, the second antenna member 420 includes a first side 421 and a third side 423 extending parallel to each other, and a second side 422 and a fourth side 424 perpendicular to the first side 421 and the third side 423. In one example, the second antenna member 420 has a rectangular shape in which the lengths of the first side 421 and the third side 423 are greater than the lengths of the second side 422 and the fourth side 424. In one example, the second antenna member 420 is disposed such that the first side 421 and the third side 423 extend in the X-axis direction in a plan view. The second antenna member 420 may be square-shaped in which the lengths of the first side 421 and the third side 423 are equal to the lengths of the second side 422 and the fourth side 424. The second antenna member 420 may also be rectangular-shaped in which the lengths of the second side 422 and the fourth side 424 are greater than the lengths of the first side 421 and the third side 423.

[0176] The terahertz device 40 includes a first active element 450 and a second active element 460 provided in a slot 401. The first active element 450 and the second active element 460 are disposed within the slot 401 in a plan view. Therefore, the first active element 450 and the second active element 460 can be said to be disposed between a first antenna member 410 and a second antenna member 420. The end faces of the conductive layer 400 (the first antenna member 410 and the second antenna member 420) facing the annular slot 401 constitute a ring slot antenna 402. Therefore, the conductive layer 400 can be said to be a member that constitutes the ring slot antenna in the terahertz device 40. The conductive layer 400 can also be said to be the antenna of the terahertz device 40. The antenna includes the first antenna member 410 and the second antenna member 420. Therefore, the first antenna member 410 can be said to be the first antenna member of the antenna, and the second antenna member 420 can be said to be the second antenna member of the antenna.

[0177] The first active element 450 and the second active element 460 are elements that convert electromagnetic waves into electrical energy. Note that the term "electromagnetic waves" encompasses the concepts of either light or radio waves, or both. The first active element 450 and the second active element 460 are elements that emit electromagnetic waves (terahertz waves) in a predetermined frequency band, for example, the terahertz band. In this case, the first active element 450 and the second active element 460 can be considered as terahertz elements that emit terahertz waves. Furthermore, for example, the first active element 450 and the second active element 460 are elements that detect terahertz waves, which are electromagnetic waves in a predetermined frequency band, for example, the terahertz band. In this case, the first active element 450 and the second active element 460 can be considered as terahertz elements that receive terahertz waves. Here, the frequency band of the terahertz waves is, for example, 0.1 THz or more and 10 THz or less.

[0178] The first active element 450 and the second active element 460 convert the supplied electrical energy into electromagnetic waves by oscillating due to the supplied electrical energy. As a result, the first active element 450 and the second active element 460 oscillate electromagnetic waves in a desired frequency band. The first active element 450 and the second active element 460 also receive electromagnetic waves and convert the electromagnetic waves into electrical energy. As a result, the first active element 450 and the second active element 460 detect electromagnetic waves in a desired frequency band.

[0179] For example, the first active element 450 and the second active element 460 may be resonant tunneling diodes (RTDs). The first active element 450 and the second active element 460 may be diodes or transistors other than RTDs. The first active element 450 and the second active element 460 may be, for example, a TUNNETT diode, an IMPATT diode, a GaAs-based field effect transistor (FET), a GaN-based FET, a high electron mobility transistor (HEMT), a heterojunction bipolar transistor (HBT), a CMOSFET, or a Schottky barrier diode (SBD).

[0180] The first active element 450 and the second active element 460 have a rectangular shape in plan view. Note that the shape of the first active element 450 and the second active element 460 in plan view is not limited to a rectangular shape, and may be a circular shape, an elliptical shape, or a polygonal shape.

[0181] As shown in FIG. 37 , the first active element 450 and the second active element 460 are connected between the first antenna member 410 and the second antenna member 420. The first active element 450 and the second active element 460 are arranged on a reference line LM passing through the center 411 of the first antenna member 410 in a plan view, with the first antenna member 410 sandwiched between them. In the fourth embodiment, the reference line LM is set to extend in the X-axis direction. In the fourth embodiment, the reference line LM is parallel to the first side 421 of the second antenna member 420 in a plan view. Furthermore, the reference line LM is parallel to the side surfaces 103 and 104 of the substrate 100 in a plan view. Note that "parallel" does not only mean strictly parallel, but also includes roughly parallel arrangements within a range in which the effects of this embodiment can be achieved.

[0182] The first active element 450 and the second active element 460 are connected to the first antenna member 410 and the second antenna member 420 so as to oscillate in a state where the phases are reversed (anti-phase) to each other. The first active element 450 and the second active element 460 are connected between the first antenna member 410 and the second antenna member 420 so as to be in parallel.

[0183] 36 to 38 , the first active element 450 is connected between the second antenna member 420 and the first antenna member 410. The conductive layer 400 includes a connection portion 433 extending from the second antenna member 420 toward the first antenna member 410. The conductive layer 400 also includes a connection portion 431 extending from the first antenna member 410 toward the second antenna member 420. The first active element 450 is connected between the second antenna member 420 and the first antenna member 410 by the connection portion 433 and the connection portion 431.

[0184] The second active element 460 is connected between the first antenna member 410 and the second antenna member 420. The conductive layer 400 includes a connection portion 432 extending from the first antenna member 410 toward the second antenna member 420. The conductive layer 400 includes a connection portion 434 extending from the second antenna member 420 toward the first antenna member 410. The second active element 460 is connected between the first antenna member 410 and the second antenna member 420 by the connection portion 432 and the connection portion 434.

[0185] 36 and 37 , the terahertz device 40 includes a circuit member 500. The circuit member 500 includes a first resistor element 501 and a second resistor element 502. The first resistor element 501 and the second resistor element 502 are provided outside the slot 401. In one example, the first resistor element 501 and the second resistor element 502 are arranged at positions overlapping the second antenna member 420 in a plan view. The first resistor element 501 and the second resistor element 502 are arranged with the first antenna member 410 sandwiched therebetween. The first resistor element 501 and the second resistor element 502 are arranged at positions symmetrical with respect to the first antenna member 410. In the terahertz device 40 of the fourth embodiment, the first resistor element 501 and the second resistor element 502 are arranged at positions point-symmetrical with respect to the center 411 of the first antenna member 410.

[0186] The first resistive element 501 and the second resistive element 502 are electrically connected in parallel to the first active element 450 and the second active element 460. The first resistive element 501 and the second resistive element 502 suppress parasitic oscillation, thereby stabilizing oscillation in the terahertz device 40.

[0187] The first resistor element 501 and the second resistor element 502 are electrically connected to the first antenna member 410 at virtual short-circuit points 441, 442. It can be said that the first resistor element 501 and the second resistor element 502 are connected to both ends of the first antenna member 410 on an auxiliary line LS that passes through the center 411 of the first antenna member 410.

[0188] The virtual short-circuit points 441 and 442 are portions where the electric field strength of the terahertz waves generated by the first active element 450 and the second active element 460, which oscillate in opposite phases, is relatively low, and can be referred to as pseudo short-circuit points. The virtual short-circuit points 441 and 442 may be set in a range where the electric field strength of the terahertz waves is relatively low. The electric fields generated by the first active element 450 and the second active element 460, which oscillate in opposite phases, are added together in opposite phases. As a result, a portion where the electric field strength is relatively low occurs near the center between the first active element 450 and the second active element 460. Therefore, the location where the electric field strength is relatively low occurs equidistant from the first active element 450 and the second active element 460. As shown in FIG. 37, the area where the electric field strength is relatively low occurs along an auxiliary line LS that passes through the center 411 of the first antenna member 410 and is perpendicular to the reference line LM that passes through the first active element 450 and the second active element 460.

[0189] (Details of First Active Element and Second Active Element) Fig. 39 is a schematic plan view enlarging a portion of the terahertz device 40 of Fig. 36, showing the arrangement of the first active element 450. Fig. 40 is a schematic plan view enlarging a portion of the terahertz device 40 of Fig. 36, showing the arrangement of the second active element 460. Fig. 41 is a schematic cross-sectional view showing the first active element 450, the second active element 460, and their peripheries.

[0190] The following describes an example of a configuration for realizing the first active element 450. As shown in Figures 39 and 41 , the first active element 450 is provided between the second antenna member 420 and the substrate 100 in the Z-axis direction.

[0191] As shown in FIG. 41 , a semiconductor layer 451A is provided on the substrate surface 101 of the substrate 100. In one example, the shape of the semiconductor layer 451A is rectangular in a plan view. The semiconductor layer 451A is made of, for example, GaInAs. The semiconductor layer 451A is doped with a high concentration of n-type impurities. A GaInAs layer 452A is stacked on the semiconductor layer 451A. The GaInAs layer 452A is doped with n-type impurities. The n-type impurity concentration of the GaInAs layer 452A is lower than the n-type impurity concentration of the semiconductor layer 451A. A GaInAs layer 453A is stacked on the GaInAs layer 452A. The GaInAs layer 453A is not doped with impurities.

[0192] An AlAs layer 454A is stacked on the GaInAs layer 453A. An InGaAs layer 455 is stacked on the AlAs layer 454A. The InGaAs layer 455 is not doped with impurities. An AlAs layer 454B is stacked on the InGaAs layer 455. The AlAs layer 454A, the InGaAs layer 455, and the AlAs layer 454B form a resonant tunnel section.

[0193] An undoped GaInAs layer 453B is stacked on the AlAs layer 454B. An n-type impurity-doped GaInAs layer 452B is stacked on the GaInAs layer 453B. A highly doped GaInAs layer 451B is stacked on the GaInAs layer 452B. Therefore, the n-type impurity concentration of the GaInAs layer 451B is higher than that of the GaInAs layer 452B.

[0194] The specific configuration of first active element 450 can be changed as desired as long as it can generate (or detect, or both) electromagnetic waves. In other words, first active element 450 may be any element that performs at least one of oscillation and detection of electromagnetic waves in the terahertz band.

[0195] The connecting portion 433 extending from the second antenna member 420 extends toward the semiconductor layer 451A and is electrically connected to the semiconductor layer 451A. The connecting portion 431 extending from the first antenna member 410 contacts the upper surface of the GaInAs layer 451B and is electrically connected to the GaInAs layer 451B. In this manner, the first active element 450 is connected between the second antenna member 420 and the first antenna member 410.

[0196] The following describes an example of a configuration for realizing the second active element 460. As shown in Figures 40 and 41 , the second active element 460 is provided between the first antenna member 410 and the substrate 100 in the Z-axis direction.

[0197] As shown in FIG. 41 , a semiconductor layer 461A is provided on the substrate surface 101 of the substrate 100. In one example, the shape of the semiconductor layer 461A is rectangular in a plan view. The semiconductor layer 461A is made of, for example, GaInAs. The semiconductor layer 461A is doped with a high concentration of n-type impurities. A GaInAs layer 462A is stacked on the semiconductor layer 461A. The GaInAs layer 462A is doped with n-type impurities. The n-type impurity concentration of the GaInAs layer 462A is lower than the n-type impurity concentration of the semiconductor layer 461A. A GaInAs layer 463A is stacked on the GaInAs layer 462A. The GaInAs layer 463A is not doped with impurities.

[0198] An AlAs layer 464A is stacked on the GaInAs layer 463A. An InGaAs layer 465 is stacked on the AlAs layer 464A. The InGaAs layer 465 is not doped with impurities. An AlAs layer 464B is stacked on the InGaAs layer 465. The AlAs layer 464A, the InGaAs layer 465, and the AlAs layer 464B form a resonant tunnel section.

[0199] An undoped GaInAs layer 463B is stacked on the AlAs layer 464B. An n-type impurity-doped GaInAs layer 462B is stacked on the GaInAs layer 463B. A highly doped GaInAs layer 461B is stacked on the GaInAs layer 462B. Therefore, the n-type impurity concentration of the GaInAs layer 461B is higher than that of the GaInAs layer 462B.

[0200] The specific configuration of second active element 460 can be changed as desired as long as it can generate (or detect, or both) electromagnetic waves. In other words, second active element 460 may be any element that performs at least one of oscillation and detection of electromagnetic waves in the terahertz band.

[0201] The connecting portion 432 extending from the first antenna member 410 contacts the upper surface of the GaInAs layer 461B and is electrically connected to the GaInAs layer 461B. The connecting portion 434 extending from the second antenna member 420 extends toward the semiconductor layer 461A and is electrically connected to the semiconductor layer 461A. In this manner, the second active element 460 is connected between the first antenna member 410 and the second antenna member 420.

[0202] (Details of Resistance Element) Fig. 42 is a schematic plan view enlarging a part of the terahertz device 40 of Fig. 36, showing the arrangement of the second resistance element 502. Fig. 43 is a schematic cross-sectional view showing the second resistance element 502 of Fig. 42 and its periphery.

[0203] 43 , the second resistor element 502 is provided between the substrate 100 and the second antenna member 420. The second resistor element 502 is provided on the substrate surface 101 of the substrate 100. In one example, the second resistor element 502 has a rectangular shape in a plan view. The second resistor element 502 is made of a semiconductor layer doped with a high concentration of n-type impurities. In one example, the semiconductor layer may be GaInAs.

[0204] The second resistive element 502 includes a first end 502A and a second end 502B opposite the first end 502A. The first end 502A is electrically connected to the second antenna member 420 by a via 525 disposed on the second resistive element 502. The via 525 is made of at least one metal material selected from the group consisting of Au, Ag, Al, Cu, Ti, TiN, and Pt. It can also be said that the via 525 includes at least one of Au, Ag, Al, Cu, Ti, and Pt. In one example, the via 525 is made of a material including Au.

[0205] A lower interconnection 523 is electrically connected to the second end 502B of the second resistor element 502. The lower interconnection 523 is disposed within the insulating layer 120 in the Z-axis direction. It can be said that the lower interconnection 523 is disposed between the insulating front surface 121 and the insulating back surface 122 in the Z-axis direction. In one example, the insulating layer 120 may include a first insulating film disposed on the substrate 100 and a second insulating film disposed on the first insulating film. The first insulating film may have the same film thickness as the first resistor element 501, for example. The lower interconnection 523 may be disposed on the first insulating film. Note that the insulating layer 120 may include three or more insulating films. The lower interconnection 523 is made of at least one metal material selected from the group consisting of Au, Ag, Al, Cu, Ti, TiN, and Pt. It can also be said that the lower interconnection 523 includes at least one of Au, Ag, Al, Cu, Ti, and Pt. In one example, the lower wiring 523 is made of a material containing Au.

[0206] As shown in FIGS. 37 and 42 , the lower wiring 523 extends toward the first antenna member 410. It can be said that the lower wiring 523 extends so as to intersect with the slot 401 between the second antenna member 420 and the first antenna member 410. The lower wiring 523 is electrically connected to the first antenna member 410 by a via 524. As shown in FIG. 37 , the via 524 electrically connecting the lower wiring 523 and the first antenna member 410 is located at the virtual short point 442. The via 524 is made of at least one metal material selected from the group consisting of Au, Ag, Al, Cu, Ti, TiN, and Pt. It can also be said that the via 524 includes at least one of Au, Ag, Al, Cu, Ti, and Pt. In one example, the via 524 is made of a material including Au.

[0207] 36 and 37 , the first resistor element 501, like the second resistor element 502, is electrically connected to the first antenna member 410 and the second antenna member 420. Although not shown, the first resistor element 501 is provided on the substrate surface 101 of the substrate 100. In one example, the shape of the first resistor element 501 is rectangular in plan view. The first resistor element 501 is configured of a semiconductor layer doped with a high concentration of n-type impurities. In one example, the semiconductor layer may be GaInAs.

[0208] The first resistor element 501 includes a first end 501A and a second end 501B opposite the first end 501A. The first end 501A is electrically connected to the second antenna member 420 by a via 515 disposed on the first resistor element 501. The via 515 is made of at least one metal material selected from the group consisting of Au, Ag, Al, Cu, Ti, TiN, and Pt. It can also be said that the via 515 includes at least one of Au, Ag, Al, Cu, Ti, and Pt. In one example, the via 515 is made of a material including Au.

[0209] The lower interconnection 513 is electrically connected to the second end 501B of the first resistor element 501. The lower interconnection 513 is disposed within the insulating layer 120 in the Z-axis direction. It can be said that the lower interconnection 513 is disposed between the insulating front surface 121 and the insulating back surface 122 in the Z-axis direction. In one example, the insulating layer 120 may include a first insulating film disposed on the substrate 100 and a second insulating film disposed on the first insulating film. The first insulating film may have the same film thickness as the second resistor element 502, for example. The lower interconnection 513 may be disposed on the first insulating film. Note that the insulating layer 120 may include three or more insulating films. The lower interconnection 513 is made of at least one metal material selected from the group consisting of Au, Ag, Al, Cu, Ti, TiN, and Pt. It can also be said that the lower interconnection 523 includes at least one of Au, Ag, Al, Cu, Ti, and Pt. In one example, the lower wiring 513 is made of a material containing Au.

[0210] As shown in FIGS. 37 and 42 , the lower wiring 513 extends toward the first antenna member 410. In a plan view, the lower wiring 513 can be said to extend so as to intersect with the slot 401 between the second antenna member 420 and the first antenna member 410. The lower wiring 523 is electrically connected to the first antenna member 410 by a via 514. As shown in FIG. 37 , the via 514 electrically connecting the lower wiring 513 and the first antenna member 410 is located at the virtual short point 441. The via 524 is made of at least one metal material selected from the group consisting of Au, Ag, Al, Cu, Ti, TiN, and Pt. The via 524 can also be said to include at least one of Au, Ag, Al, Cu, Ti, and Pt. In one example, the via 524 is made of a material containing Au.

[0211] 35 and 36 , the circuit member 500 of the terahertz device 40 includes a first pad electrode 171 and a second pad electrode 172 provided on the substrate surface 101 of the substrate 100. The first pad electrode 171 and the second pad electrode 172 are arranged at the edge of the substrate 100. In one example, the first pad electrode 171 and the second pad electrode 172 are arranged on a straight line LS that passes through the virtual short-circuit points 441 and 442 and extends in the Y-axis direction.

[0212] The first pad electrode 171 is disposed on the substrate surface 101 of the substrate 100, closer to the substrate side surface 103 of the substrate 100. In one example, the first pad electrode 171 is disposed at the center of the substrate surface 101 in the X-axis direction. The first pad electrode 171 has a circular shape in a plan view. It can be said that the first pad electrode 171 includes a curved portion over the entire end portion. In one example, the width W11 of the first pad electrode 171 may be represented by its diameter in the X-axis direction. The width W11 of the first pad electrode 171 may be smaller than the lengths Lx and Ly of the conductive layer 400, which serves as an antenna. The first pad electrode 171 is made of at least one metal material selected from the group consisting of Au, Ag, Al, Cu, Ti, TiN, and Pt. In one example, the first pad electrode 171 is made of a material containing Au.

[0213] The second pad electrode 172 is disposed on the substrate surface 101 of the substrate 100, closer to the substrate side surface 105 of the substrate 100. In one example, the second pad electrode 172 is disposed at the center of the substrate surface 101 in the X-axis direction. The second pad electrode 172 has a circular shape in a plan view. It can be said that the second pad electrode 172 includes a curved portion over the entire end portion. In one example, the width W12 of the second pad electrode 172 may be represented by its diameter in the X-axis direction. The width W12 of the second pad electrode 172 may be smaller than the lengths Lx and Ly of the conductive layer 400, which serves as an antenna. The width W12 of the second pad electrode 172 may be equal to or different from the width W11 of the first pad electrode 171. The second pad electrode 172 is made of at least one metal material selected from the group consisting of Au, Ag, Al, Cu, Ti, TiN, and Pt. In one example, the second pad electrode 172 is made of a material containing Au.

[0214] The circuit member 500 of the terahertz device 40 includes a first wiring member 510 that connects the first pad electrode 171 and the first antenna member 410. The first wiring member 510 is preferably connected to the first antenna member 410 at a virtual short-circuit point 441. By connecting the first wiring member 510 to the first antenna member 410 at the virtual short-circuit point 441 in this manner, leakage of electromagnetic waves to the first wiring member 510 can be suppressed.

[0215] In one example, the first wiring member 510 includes a first wiring 511, a via 512, a lower wiring 513, and vias 514 and 515. The first wiring 511 extends in the Y-axis direction from the first pad electrode 171 toward the first antenna member 410. The lower wiring 513 extends in the Y-axis direction from the tip of the first wiring 511. The lower wiring 513 is electrically connected to the first wiring 511 by the via 512. The via 514 is connected to the tip of the lower wiring 513. The lower wiring 513 is electrically connected to the first antenna member 410 by the via 514. The via 514 may be disposed at the virtual short point 441. The first wiring member 510 connects the first pad electrode 171 to the virtual short point 441 of the first antenna member 410. The first wiring 511 of the first wiring member 510 may be arranged on a path different from that of the lower wiring 513 and connected to the first antenna member 410 .

[0216] The lower wiring 513 and the vias 514, 515 are used to connect the first resistor element 501 to the conductive layer 400 that serves as the antenna. The lower wiring 513, the vias 514, 515, and the first resistor element 501 are included in a first wiring member 510 that is electrically connected to the conductive layer 400 that serves as the antenna.

[0217] The circuit member 500 of the terahertz device 40 includes a second wiring member 520 that connects the second pad electrode 172 and the second antenna member 420. The second wiring member 520 electrically connects the second pad electrode 172 and the second antenna member 420. The second wiring member 520 is preferably connected to the second antenna member 420 at a virtual short point 442.

[0218] In one example, the second wiring member 520 includes a first wiring 521, a lower wiring 523, and vias 524 and 525. The first wiring 521 extends in the Y-axis direction from the second pad electrode 172 toward the second antenna member 420. The tip of the first wiring 521 is electrically connected to the second antenna member 420. In the terahertz device 40 of the fourth embodiment, the second pad electrode 172 is connected to the second antenna member 420 by the second wiring member 520 at a point where an auxiliary line LS passing through the virtual short point 442 intersects with the third side 423 of the second antenna member 420. It can be said that the second wiring member 520 is connected to the second antenna member 420 on the auxiliary line LS passing through the virtual short point 442. In this way, by connecting the second wiring member 520 near the virtual short point 442, leakage of electromagnetic waves to the second wiring member 520 can be suppressed.

[0219] The lower wiring 523 and the vias 524, 525 are used to connect the second resistor element 502 to the conductive layer 400 that serves as the antenna. The lower wiring 523, the vias 524, 525, and the second resistor element 502 are included in a second wiring member 520 that is electrically connected to the conductive layer 400 that serves as the antenna.

[0220] (Back Metal Layer) The terahertz device 40 may include a back metal layer 125. The back metal layer 125 is provided on the back surface 102 of the substrate 100. The back metal layer 125 is in contact with the back surface 102 of the substrate 100. The back metal layer 125 includes a reflective surface 126 and a reflective back surface 127 opposite to the reflective surface 126. The reflective surface 126 is in contact with the back surface 102 of the substrate.

[0221] The back surface metal layer 125 may cover at least a portion of the back surface 102 of the substrate 100. The back surface metal layer 125 may be arranged so as to overlap the antenna 150 in a plan view. In one example, the back surface metal layer 125 is provided over the entire back surface 102 of the substrate 100. It can be said that the back surface metal layer 125 covers the entire back surface 102 of the substrate 100. The back surface metal layer 125 may have a thickness that allows it to reflect electromagnetic waves generated or detected by the first active element 450 and the second active element 460. The back surface metal layer 125 may be said to be a reflective layer that reflects electromagnetic waves.

[0222] The back surface metal layer 125 is composed of a metal layer provided on the back surface 102 of the substrate 100. The back surface metal layer 125 is composed of at least one metal material selected from the group consisting of Au, Ag, Al, Cu, Ti, TiN, and Pt. It can also be said that the back surface metal layer 125 contains at least one of Au, Ag, Al, Cu, Ti, and Pt. In one example, the back surface metal layer 125 is composed of a material containing Au. The back surface metal layer 125 may be composed of the same material as the conductive layer 400. The back surface metal layer 125 may also be composed of a stacked structure of multiple metal layers.

[0223] (Operation of Fourth Embodiment) The terahertz device 40 includes a substrate 100, a conductive layer 400, a slot 401, a first active element 450, and a second active element 460. The substrate 100 includes a substrate front surface 101 and a substrate back surface 102, and the conductive layer 400 is formed in a portion of the substrate front surface 101. The slot 401 is formed in the conductive layer 400. The slot 401 is formed in an annular shape. The first active element 450 and the second active element 460 are provided within the slot 401. The conductive layer 400 includes a first antenna member 410 defined by the slot 401, and a second antenna member 420 formed to surround the first antenna member 410 via the slot 401. The end faces of the conductive layer 400 (the first antenna member 410 and the second antenna member 420) facing the annular slot 401 form a ring slot antenna 402. In this terahertz device 40, the output power (output electric power) of the terahertz device 40 can be improved by causing the first active element 450 and the second active element 460 to oscillate.

[0224] (Effects of Fourth Embodiment) As described above, the terahertz device 40 of the fourth embodiment provides the following effects.

[0225] (4-1) The first pad electrode 171 has a circular shape in a plan view. The first pad electrode 171 is curved around the entire edge. Therefore, it is possible to reduce the reflection of electromagnetic waves at the first pad electrode 171. As a result, the terahertz device 40 can suppress the generation of electromagnetic waves with frequencies different from those of the desired frequency.

[0226] (4-2) The second pad electrode 172 has a circular shape in a plan view. The second pad electrode 172 is curved around the entire edge. Therefore, it is possible to reduce the reflection of electromagnetic waves at the second pad electrode 172. As a result, the terahertz device 40 can suppress the generation of electromagnetic waves with frequencies different from the electromagnetic waves with the desired frequency.

[0227] (4-3) The terahertz device 40 includes a first active element 450 and a second active element 460. By causing the first active element 450 and the second active element 460 to oscillate, the output power (output electric power) of the terahertz device 40 can be improved.

[0228] (4-4) The terahertz device 40 includes a first resistive element 501 and a second resistive element 502 connected in parallel to the first active element 450 and the second active element 460. This allows the oscillation in the terahertz device 40 to be stabilized.

[0229] (4-5) The terahertz device 40 includes a back surface metal layer 125 provided on the back surface 102 of the substrate 100. The back surface metal layer 125 reflects electromagnetic waves radiated from the ring slot antenna 402 toward the substrate 100. Therefore, the terahertz device 40 can radiate electromagnetic waves in the direction in which the front surface 101 of the substrate 100 faces.

[0230] (4-6) The first pad electrode 171 is connected to the first antenna member 410 by a first wiring member 510. The first wiring member 510 is connected to a virtual short-circuit point 441 of the first antenna member 410. By connecting the first wiring member 510 to the virtual short-circuit point 441, leakage of electromagnetic waves to the first wiring member 510 can be suppressed.

[0231] (4-7) The second pad electrode 172 is connected to the second antenna member 420 by the second wiring member 520. The second wiring member 520 is connected to the second antenna member 420 on an auxiliary line LS that passes through the virtual short-circuit point 442. By connecting the second wiring member 520 to the second antenna member 420 in the vicinity of the virtual short-circuit point, leakage of electromagnetic waves to the second wiring member 520 can be suppressed.

[0232] (Modifications of the Fourth Embodiment) The fourth embodiment can be modified, for example, as follows. The fourth embodiment can be combined with the following modifications as long as no technical contradiction occurs. In the following modifications, parts common to the fourth embodiment are designated by the same reference numerals as in the fourth embodiment, and their description will be omitted.

[0233] As shown in FIG. 44 , the conductive layer 400 of a terahertz device 40A of a modified example may include a curved portion 230. The curved portion 230 may be provided in a second antenna member 420A of the conductive layer 400. In a plan view, the second antenna member 420A has a rectangular shape including a first corner portion 425, a second corner portion 426, a third corner portion 427, and a fourth corner portion 428. The second antenna member 420A (conductive layer 400) includes curved portions 230 at each of the first to fourth corner portions 425 to 428. Unlike the second antenna member 420 of the fourth embodiment, the second antenna member 420A of this terahertz device 40A does not have corners. Therefore, this terahertz device 40A can suppress radiation from the outer peripheral edge of the second antenna member 420A, i.e., the outer peripheral edge of the conductive layer 400. Therefore, the terahertz device 40A can improve the radiation pattern.

[0234] As shown in FIG. 45 , the conductive layer 400 of the modified terahertz device 40B includes a second antenna member 420B. The second antenna member 420B has an elliptical shape in a planar view. That is, the conductive layer 400 has an elliptical outer peripheral edge in a planar view. The second antenna member 420B of this terahertz device 40B does not have corners, unlike the second antenna member 420 of the fourth embodiment. Therefore, this terahertz device 40B can further suppress radiation from the outer peripheral edge of the second antenna member 420B, i.e., the outer peripheral edge of the conductive layer 400. As a result, the terahertz device 40B can further improve its radiation pattern.

[0235] As shown in FIG. 46 , a circuit member 500C of a modified terahertz device 40C includes an upper wiring 531 arranged to straddle the slot 401. More specifically, the modified terahertz device 40C includes a first wiring member 510C that electrically connects the first pad electrode 171 and the first antenna member 410. The first wiring member 510C includes a first wiring 511, a lower wiring 513, vias 514 and 515, an upper wiring 531, and vias 532 and 533. The terahertz device 40C includes an insulating layer 534 formed on the conductive layer 400. The upper wiring 531 is arranged on the insulating layer 534. The upper wiring 531 is electrically connected to the first wiring 511 by a via 532 that penetrates the insulating layer 534. The upper wiring 531 is then electrically connected to the first antenna member 410 by a via 533 that penetrates the insulating layer 534. The via 533 may be located at the virtual short point 441 .

[0236] 47 , a circuit member 500D of a modified terahertz device 40D includes a first pad electrode 171 and a second pad electrode 172. The first pad electrode 171 and the second pad electrode 172 are provided at corners of the substrate 100.

[0237] The first pad electrode 171 is disposed at the first corner 111. The second pad electrode 172 is disposed at the third corner 113. The third corner 113 is located at a diagonal corner of the substrate 100 with respect to the first corner 111. It can be said that the first pad electrode 171 and the second pad electrode 172 are disposed at two diagonally opposite corners of the substrate 100.

[0238] The circuit member 500D includes a first wiring member 510D that electrically connects the first pad electrode 171 and the first antenna member 410, and a second wiring member 520D that electrically connects the second pad electrode 172 and the second antenna member 420.

[0239] The first wiring member 510D includes a first wiring portion 511D connected to the first pad electrode 171. The first wiring portion 511D includes a first wiring 516, a second wiring 517, and a curved portion 518. The first wiring 516 is electrically connected to the first pad electrode 171 and extends from the first pad electrode 171 in the X-axis direction toward the substrate side surface 106. The second wiring 517 is electrically connected to the via 512 and extends from the via 512 in the Y-axis direction toward the substrate side surface 103. The curved portion 518 is curved so as to electrically connect the first wiring 516 extending in the X-axis direction with the second wiring 517 extending in the Y-axis direction.

[0240] In one example, the first wiring 516, the second wiring 517, and the curved portion 518 may have the same width. The widths of the first wiring 516, the second wiring 517, and the curved portion 518 are smaller than the width W11 of the first pad electrode 171. The first wiring 516 and the second wiring 517 may have different widths.

[0241] The first wiring member 510D includes a curved portion 518. This allows electric field concentration in the first wiring member 510D to be alleviated compared to when the first wiring 516 and the second wiring 517 are connected at a right angle. The curved portion 518 allows the terahertz device 40D to reduce reflection of electromagnetic waves. This allows the terahertz device 40D to suppress the generation of electromagnetic waves with frequencies different from those of the desired frequency.

[0242] The second wiring member 520D includes a first wiring portion 521D connected to the second pad electrode 172. The first wiring portion 521D includes a first wiring 526, a second wiring 527, and a curved portion 528. The first wiring 526 is electrically connected to the second pad electrode 172 and extends from the second pad electrode 172 in the X-axis direction toward the substrate side surface 104. The second wiring 527 is electrically connected to the second antenna member 420 and extends from the second antenna member 420 in the Y-axis direction toward the substrate side surface 105. The curved portion 528 is curved so as to electrically connect the first wiring 526 extending in the X-axis direction with the second wiring 527 extending in the Y-axis direction.

[0243] In one example, the first wiring 526, the second wiring 527, and the curved portion 528 may have the same width. The widths of the first wiring 526, the second wiring 527, and the curved portion 528 are smaller than the width W12 of the second pad electrode 172. The first wiring 526 and the second wiring 527 may have different widths.

[0244] The second wiring member 520D includes a curved portion 528. This allows electric field concentration in the second wiring member 520D to be alleviated compared to when the first wiring 526 and the second wiring 527 are connected at a right angle. The curved portion 528 allows the terahertz device 40D to reduce reflection of electromagnetic waves. This allows the terahertz device 40D to suppress the generation of electromagnetic waves with frequencies different from those of the desired frequency.

[0245] 47, the second pad electrode 172 may be arranged at a second corner 112 formed by the substrate side surface 104 and the substrate side surface 105 on the substrate surface 101 of the substrate 100. Although not shown, the first pad electrode 171 may be arranged at a fourth corner 114 compared to FIG. 26. Furthermore, the second pad electrode 172 may be arranged at the second corner 112, and the first pad electrode 171 may be arranged at the fourth corner 114 diagonally opposite the second corner 112.

[0246] In the terahertz device 40D of this modified example, the first pad electrode 171 and the second pad electrode 172 may be disposed at the corners 111, 113 of the substrate 100. This makes it possible to prevent the first pad electrode 171 and the second pad electrode 172 from blocking the electromagnetic waves that are reflected by the back surface metal layer 125 and head toward the substrate surface 101.

[0247] 48 includes a circuit member 500E of a terahertz device 40E according to a modified example. The circuit member 500E includes a first pad electrode 171 and a second pad electrode 172. The first pad electrode 171 is disposed at the first corner 111. The second pad electrode 172 is disposed at the fourth corner 114.

[0248] The circuit member 500E includes a first wiring member 510D that electrically connects the first pad electrode 171 and the first antenna member 410, and a second wiring member 520E that electrically connects the second pad electrode 172 and the second antenna member 420.

[0249] The second wiring member 520E includes a first wiring portion 521E connected to the second pad electrode 172. The first wiring portion 521E includes a first wiring 526, a second wiring 527, and a curved portion 528. The first wiring 526 is electrically connected to the second pad electrode 172 and extends from the second pad electrode 172 in the X-axis direction toward the substrate side surface 104. The second wiring 527 is electrically connected to the second antenna member 420 and extends from the second antenna member 420 in the Y-axis direction toward the substrate side surface 103. The second wiring 527 is electrically connected to the second antenna member 420 near the auxiliary line LS, which serves as the virtual short-circuit point. In this way, connecting the second wiring member 520E to the second antenna member 420 near the virtual short-circuit point can suppress leakage of electromagnetic waves to the second wiring member 520E. The curved portion 528 is curved so as to electrically connect the first wiring 526 extending in the X-axis direction and the second wiring 527 extending in the Y-axis direction.

[0250] In one example, the first wiring 526, the second wiring 527, and the curved portion 528 may have the same width. The widths of the first wiring 526, the second wiring 527, and the curved portion 528 are smaller than the width W12 of the second pad electrode 172. The first wiring 526 and the second wiring 527 may have different widths.

[0251] The second wiring member 520E includes a curved portion 528. This allows electric field concentration in the second wiring member 520E to be alleviated compared to when the first wiring 526 and the second wiring 527 are connected at a right angle. The curved portion 528 allows the terahertz device 40E to reduce reflection of electromagnetic waves. This allows the terahertz device 40E to suppress the generation of electromagnetic waves with frequencies different from those of the desired frequency.

[0252] As shown in Fig. 49 , the terahertz device 40F of the modified example includes fillet portions 519 and 529 in addition to the configuration of the terahertz device 40E of the modified example shown in Fig. 48 . The fillet portion 519 is provided between the first pad electrode 171 and the first wiring 516. The fillet portion 519 has a shape that widens from the first wiring 516 toward the first pad electrode 171. This fillet portion 519 acts as a curved portion between the first wiring member 510D and the first pad electrode 171. Therefore, compared to a device that does not include the fillet portion 519, this terahertz device 40F can further alleviate electric field concentration and thereby further reduce electromagnetic wave reflection.

[0253] The fillet portion 529 is provided between the second pad electrode 172 and the first wiring 526. The fillet portion 529 has a shape that widens from the first wiring 526 toward the second pad electrode 172. This fillet portion 529 acts as a curved portion between the second wiring member 520E and the second pad electrode 172. Therefore, compared to a device that does not include the fillet portion 529, this terahertz device 40F can further alleviate electric field concentration and therefore further reduce electromagnetic wave reflection.

[0254] 50 to 53, a terahertz device 50 according to a fifth embodiment will be described. Note that, in the terahertz device 50 according to the fifth embodiment, components similar to those of the terahertz device 40 according to the fourth embodiment are denoted by the same reference numerals. Below, a description of the components similar to those of the fourth embodiment will be omitted, and components different from those of the fourth embodiment will be described.

[0255] FIG. 50 is a schematic plan view of an exemplary terahertz device 50 of the fifth embodiment. FIG. 51 is a schematic plan view showing the second active element 460 of FIG. 50 and its periphery. The second active element 460 and the second resistive element 502 are shown in FIG. 51. FIG. 52 is a schematic plan view showing the first active element 450 of FIG. 50 and its periphery. The first active element 450 and the first resistive element 501 are shown in FIG. 53. FIG. 53 is a schematic cross-sectional view showing the first active element 450 of FIG. 50 and its periphery. The first active element 450 and the first resistive element 501 are shown in FIG.

[0256] 50 , a terahertz device 50 according to the fifth embodiment includes a first resistive element 501 and a second resistive element 502 that are arranged to overlap with a first active element 450 and a second active element 460 in a plan view. The first resistive element 501 is connected in parallel to the first active element 450. The second resistive element 502 is connected in parallel to the second active element 460.

[0257] 52 , the first resistor element 501 is disposed so as to overlap the first active element 450 in a plan view. The first resistor element 501 includes a first end 501A and a second end 501B. The second end 501B of the first resistor element 501 is electrically connected to the first active element 450. The first end 501A of the first resistor element 501 is disposed so as to overlap the first antenna member 410. The first end 501A of the first resistor element 501 is electrically connected to the first antenna member 410 by a via 515.

[0258] 51 , the second resistor element 502 is disposed so as to overlap the second active element 460 in a plan view. The second resistor element 502 includes a first end 502A and a second end 502B. The second end 502B of the second resistor element 502 is electrically connected to the second active element 460. The first end 502A of the second resistor element 502 is disposed so as to overlap the first antenna member 410. The first end 502A of the second resistor element 502 is electrically connected to the first antenna member 410 by a via 525.

[0259] 53 , the first resistor element 501 is disposed on the substrate surface 101 of the substrate 100. The first resistor element 501 is disposed adjacent to the semiconductor layer 451A of the first active element 450. The GaInAs layer 452A of the first active element 450 is disposed so as to overlap both the semiconductor layer 451A and the first resistor element 501.

[0260] The semiconductor layer 451A and the first resistor element 501 may be made of the same material. In one example, the semiconductor layer 451A and the first resistor element 501 are made of GaInAs. The semiconductor layer 451A and the first resistor element 501 may be heavily doped with n-type impurities. The first resistor element 501 may be formed integrally with the semiconductor layer 451A. In FIG. 53 , the boundary between the semiconductor layer 451A and the first resistor element 501 is indicated by a dashed line, but this dashed line does not necessarily mean that there is an actually observable boundary. Although not shown, the second resistor element 502 is configured similarly to the first resistor element 501.

[0261] The terahertz device 50 of the fifth embodiment functions as a detector that detects terahertz waves. As shown in Figures 50 to 52, the first resistor element 501 is electrically connected in parallel with the first active element 450. The second resistor element 502 is electrically connected in parallel with the second active element 460. The first resistor element 501 and the second resistor element 502 of the fifth embodiment can suppress oscillation of the first active element 450 and the second active element 460.

[0262] (Effects of Fifth Embodiment) According to the terahertz device 50 of the fifth embodiment, the following effects are achieved in addition to the effects of the fourth embodiment.

[0263] (5-1) Similar to the terahertz device 40 of the fourth embodiment, the terahertz device 50 of the fifth embodiment includes a first active element 450 and a second active element 460 arranged on either side of the first antenna member 410. The terahertz device 50 of the fifth embodiment detects terahertz waves using the first active element 450 and the second active element 460. Therefore, the terahertz device 50 of the fifth embodiment can improve detection sensitivity.

[0264] (5-2) The terahertz device 50 of the fifth embodiment includes a first resistive element 501 arranged to overlap the first active element 450, and a second resistive element 502 arranged to overlap the second active element 460. The first resistive element 501 and the second resistive element 502 suppress oscillation of the first active element 450 and the second active element 460. Therefore, the terahertz device 50 of the fifth embodiment can suppress oscillation of the first active element 450 and the second active element 460.

[0265] Sixth Embodiment A terahertz device 60 according to a sixth embodiment will be described with reference to Fig. 54. Note that in the terahertz device 60 according to the sixth embodiment, components similar to those in the terahertz devices 40 and 50 according to the fourth and fifth embodiments are denoted by the same reference numerals. Below, a description of the components similar to those in the fourth and fifth embodiments will be omitted, and only components different from those in the fourth and fifth embodiments will be described.

[0266] 54 is a schematic plan view of an exemplary terahertz device 60 according to the sixth embodiment. The terahertz device 60 according to the sixth embodiment differs from the terahertz device 40 according to the fourth embodiment shown in FIG. 36 mainly in that the terahertz device 60 includes a plurality of dummy pad electrodes 540.

[0267] The dummy pad electrodes 540 are arranged at the corners 111 to 114 of the substrate 100. The first pad electrode 171 is arranged closer to the substrate side surface 103 of the substrate 100. The first pad electrode 171 is arranged in the center of the substrate surface 101 in the X-axis direction. The first pad electrode 171 is arranged between the first corner 111 and the fourth corner 114 in the X-axis direction. The second pad electrode 172 is arranged closer to the substrate side surface 105 of the substrate 100. The second pad electrode 172 is arranged in the center of the substrate surface 101 in the X-axis direction. The second pad electrode 172 is arranged between the second corner 112 and the third corner 113 in the X-axis direction.

[0268] The plurality of dummy pad electrodes 540 are arranged at the four corners 111 to 114 of the substrate 100. As described above, the first pad electrode 171 is arranged between the first corner 111 and the fourth corner 114, and the second pad electrode 172 is arranged between the second corner 112 and the third corner 113. In other words, the first pad electrode 171 and the second pad electrode 172 are not arranged at the first to fourth corners 111 to 114. It can be said that the plurality of dummy pad electrodes 540 are arranged at the corners 111 to 114 of the substrate 100 where the first pad electrode 171 and the second pad electrode 172 are not arranged.

[0269] In one example, the multiple dummy pad electrodes 540 have a circular shape in a plan view. The multiple dummy pad electrodes 540 are curved around the entire circumference. It can be said that the multiple dummy pad electrodes 540 include the curved portion 230 over the entire end portion. The multiple dummy pad electrodes 540 may have a shape that includes the curved portion 230 in at least a part of the end portion.

[0270] The first pad electrode 171 and the second pad electrode 172 are provided with bumps 541. Similarly, the plurality of dummy pad electrodes 540 are provided with bumps 541. The bumps 541 may be formed, for example, with a laminated structure of a metal layer containing Cu, a metal layer containing Ti, and a metal layer containing Sn. The bumps 541 may also have a single-layer structure. The bumps 541 may also be omitted.

[0271] The terahertz device 60 of the sixth embodiment is used in the terahertz unit 900 in place of the terahertz device 30 of the third embodiment. The terahertz device 60 of the sixth embodiment can be flip-chip mounted on the conductive parts 961 and 962 shown in FIG. 32 , similar to the terahertz device 30 of the third embodiment.

[0272] (Effects of Sixth Embodiment) As described above, the terahertz device 60 of the sixth embodiment has the following effects in addition to the effects of the fourth embodiment.

[0273] (6-1) The terahertz device 60 of the sixth embodiment includes a first pad electrode 171 and a second pad electrode 172 used to apply a voltage to the active element 130 or to transmit a signal detected by the active element 130. The first pad electrode 171 and the second pad electrode 172 are electrically connected to the conductive portions 961 and 962 by the bumps 541. Therefore, the length of the transmission path of the signal or the like can be shortened compared to when a wire or the like is connected to the first pad electrode 171 and the second pad electrode 172. Furthermore, the inductance in the transmission path can be reduced.

[0274] (6-2) The terahertz device 60 of the sixth embodiment can be mounted on the support substrate 810 of the terahertz unit 800, similar to the terahertz device 10 of the first embodiment. Furthermore, the terahertz device 60 of the sixth embodiment can be applied to the terahertz unit 900. In this way, the terahertz device 60 can be used in various terahertz units.

[0275] (6-3) The terahertz device 60 includes a plurality of dummy pad electrodes 540. The plurality of dummy pad electrodes 540 are arranged at the four corners 111 to 114 of the substrate 100. The plurality of dummy pad electrodes 540 are connected to dummy conductive portions by bumps 541. This makes it possible to prevent the substrate 100 of the terahertz device 60 from tilting with respect to the direction in which electromagnetic waves are emitted or incident, such as the antenna surface 923.

[0276] (6-4) The terahertz device 60 is mounted using the first pad electrode 171, the second pad electrode 172, and a plurality of dummy pad electrodes 540. Therefore, compared to a device that does not include the dummy pad electrodes 540, the connection to the mounting object can be made stronger.

[0277] (6-5) Stress on the terahertz device 60 is applied to the first pad electrode 171, the second pad electrode 172, and the plurality of dummy pad electrodes 540. Therefore, the dummy pad electrode 540 can relieve stress on the first pad electrode 171 and the second pad electrode 172.

[0278] (6-6) In one example, the multiple dummy pad electrodes 540 have a circular shape in a planar view. The multiple dummy pad electrodes 540 are curved around the entire circumference. It can be said that the multiple dummy pad electrodes 540 include the curved portion 230 over the entire end portion. Therefore, reflection of electromagnetic waves by the multiple dummy pad electrodes 540 is suppressed. Therefore, the terahertz device 60 can suppress the generation of electromagnetic waves with frequencies different from electromagnetic waves with a desired frequency.

[0279] (Modifications of the Sixth Embodiment) The sixth embodiment can be modified, for example, as follows. The sixth embodiment can be combined with the following modifications as long as no technical contradiction occurs. In the following modifications, parts common to the sixth embodiment are designated by the same reference numerals as in the sixth embodiment, and their description will be omitted.

[0280] As shown in Fig. 55, a terahertz device 60A of the modified example differs from the terahertz device 40D shown in Fig. 47 in that it includes a plurality of dummy pad electrodes 540. The first pad electrode 171 is disposed at the first corner 111 of the substrate 100, and the second pad electrode 172 is disposed at the third corner 113 of the substrate 100. The dummy pad electrodes 540 are disposed at the second corner 112 and the fourth corner 114 of the substrate 100. This terahertz device 60A has the same effects as the terahertz device 60 of the sixth embodiment.

[0281] As shown in Fig. 56, a terahertz device 60B of a modified example differs from the terahertz device 40E shown in Fig. 48 in that it includes a plurality of dummy pad electrodes 540. The first pad electrode 171 is disposed at the first corner 111 of the substrate 100, and the second pad electrode 172 is disposed at the fourth corner 114 of the substrate 100. The dummy pad electrodes 540 are disposed at the second corner 112 and the third corner 113 of the substrate 100. This terahertz device 60B achieves the same effects as the terahertz device 60 of the sixth embodiment.

[0282] (Other Modifications) The above embodiment and modifications can be modified, for example, as follows. The above embodiment and each of the following modifications can be combined with each other as long as no technical contradiction occurs. In the following modifications, parts that are common to the above embodiment will be assigned the same reference numerals as in the above embodiment, and their description will be omitted.

[0283] The backside metal layer 125 may be omitted. The substrate 100 may be composed of multiple stacked substrates, including semiconductor substrates. The term "on" as used in this disclosure includes both "on" and "above" unless the context clearly indicates otherwise. Thus, the expression "a first layer is disposed on a second layer" is intended to mean that in some embodiments, the first layer may be disposed directly on the second layer in contact with the second layer, while in other embodiments, the first layer may be disposed above the second layer without contacting the second layer. In other words, the term "on" does not exclude a structure in which another layer is disposed between the first layer and the second layer.

[0284] The Z-axis direction used in this disclosure does not necessarily have to be the vertical direction, nor does it have to completely coincide with the vertical direction. Therefore, various structures according to this disclosure (for example, the structure shown in FIG. 1 ) are not limited to the "up" and "down" in the Z-axis direction described in this disclosure being "up" and "down" in the vertical direction. For example, the X-axis direction may be the vertical direction, or the Y-axis direction may be the vertical direction.

[0285] [Notes] The technical ideas that can be understood from the present disclosure are described below. Note that, for the purpose of aiding understanding and not intending to be limiting, the components described in the notes are given the reference symbols of the corresponding components in the embodiments. The reference symbols are shown as examples to aid understanding, and the components described in each note should not be limited to the components indicated by the reference symbols.

[0286] [Supplementary Note 1] A terahertz device comprising: a substrate (100) including a first surface (101); an active element (130, 450, 460) provided on the first surface (101) and configured to oscillate or detect electromagnetic waves; an antenna (150, 400) electrically connected to the active element (130, 450, 460); and a circuit member (160, 500) provided on the first surface (101) and electrically connected to the antenna (150, 400), wherein the circuit member (160, 500) includes a curved portion (230) that is curved in a planar view when viewed from a direction perpendicular to the first surface (101).

[0287] [Supplementary Note 2] The terahertz device according to Supplementary Note 1, wherein the circuit member (160, 500) includes a pad electrode used to apply a voltage to the active element (130, 450, 460) or to transmit a signal detected by the active element (130, 450, 460), and the curved portion (230) is provided at an end of the pad electrode.

[0288] [Supplementary Note 3] The terahertz device according to Supplementary Note 2, wherein the pad electrode includes one or more corner portions, and the curved portion (230) is provided at the corner portion.

[0289] [Supplementary Note 4] The terahertz device according to Supplementary Note 2, wherein the pad electrode includes a first corner portion and a second corner portion that is arranged closer to the active element (130, 450, 460) than the first corner portion, and the curved portion (230) is provided at the second corner portion.

[0290] [Supplementary Note 5] The terahertz device according to Supplementary Note 4, wherein the pad electrode includes a third corner portion diagonally opposite to the first corner portion and a fourth corner portion diagonally opposite to the second corner portion, and the curved portion (230) is provided at the fourth corner portion.

[0291] [Supplementary Note 6] The terahertz device according to Supplementary Note 4, wherein the pad electrode includes a third corner portion diagonally opposite to the first corner portion and a fourth corner portion diagonally opposite to the second corner portion, and the curved portion (230) is provided at the third corner portion.

[0292] [Supplementary Note 7] The terahertz device according to any one of Supplementary Note 2 to Supplementary Note 6, wherein the curved portion (230) has an arc shape that is convex outward.

[0293] [Supplementary Note 8] The terahertz device according to any one of Supplementary Note 2 to Supplementary Note 7, wherein the curved portion (230) is formed over at least half of the circumference of the pad electrode, and the pad electrode includes a portion that is semicircular in plan view.

[0294] [Supplementary Note 9] The terahertz device according to Supplementary Note 2, wherein the pad electrode has a rectangular shape having four corners, and the curved portion (230) is provided at each of the four corners.

[0295] [Supplementary Note 10] The terahertz device according to Supplementary Note 9, wherein a side between two adjacent curved portions (230) is linear.

[0296] [Supplementary Note 11] The terahertz device according to Supplementary Note 9, wherein a side between two adjacent curved portions (230) is curved so as to be convex outward.

[0297] [Supplementary Note 12] The terahertz device according to Supplementary Note 11, wherein the radius of curvature of the curved portion (230) is smaller than the radius of curvature of the side.

[0298] [Supplementary Note 13] The terahertz device according to Supplementary Note 2, wherein the curved portion (230) is formed around the entire periphery of the pad electrode, and the pad electrode has a circular shape in the plan view.

[0299] [Supplementary Note 14] The terahertz device according to any one of Supplementary Note 2 to Supplementary Note 13, wherein the pad electrodes include a first pad electrode and a second pad electrode electrically connected to the antenna (150, 400).

[0300] [Supplementary Note 15] The terahertz device according to Supplementary Note 14, wherein the first pad electrode and the second pad electrode are arranged on either side of the antenna (150, 400), and in the planar view, the first pad electrode and the second pad electrode are symmetrical with respect to the antenna (150, 400).

[0301] [Supplementary Note 16] The terahertz device according to Supplementary Note 14, wherein the first pad electrode and the second pad electrode are arranged on either side of the antenna (150, 400), and the first pad electrode and the second pad electrode have the same shape in the planar view.

[0302] [Supplementary Note 17] The terahertz device according to any one of Supplementary Note 14 to Supplementary Note 16, wherein the first pad electrode and the second pad electrode are arranged in the center portions of two sides of the substrate (100) that sandwich the antenna (150, 400) in the planar view.

[0303] [Supplementary Note 18] The terahertz device according to Supplementary Note 14, wherein the first pad electrode and the second pad electrode are arranged at corners at both ends of one of two sides of the substrate (100) that sandwich the antenna (150, 400) in the planar view.

[0304] [Supplementary Note 19] The terahertz device described in Supplementary Note 14, wherein the substrate (100) has a rectangular shape including four corners in a planar view, the first pad electrode (171) is arranged at one of the four corners, and the second pad electrode (172) is arranged at a corner diagonally opposite the corner at which the first pad electrode is arranged.

[0305] [Supplementary Note 20] The terahertz device according to any one of Supplementary Note 14 to Supplementary Note 19, wherein the substrate (100) has a rectangular shape including four corners (111 to 114) in the planar view, and includes dummy pad electrodes (330, 540) arranged at corners among the four corners where the pad electrodes (171, 172) are not arranged.

[0306] [Supplementary Note 21] The terahertz device according to Supplementary Note 20, wherein the dummy pad electrode (330, 540) includes a curved portion (230) that is curved in the plan view.

[0307] [Supplementary Note 22] The terahertz device according to Supplementary Note 20 or Supplementary Note 21, wherein the dummy pad electrode (330, 540) is electrically insulated from the circuit member (160, 500).

[0308] [Supplementary Note 23] The terahertz device according to any one of Supplementary Note 14 to Supplementary Note 22, wherein the antenna (150, 400) includes a first antenna member (151, 410) and a second antenna member (152, 420) between which the active element (130, 450, 460) is electrically connected, and the circuit member (160, 500) includes: a first wiring member (200, 510) that electrically connects the first pad electrode (171) and the first antenna member (151, 410), and a second wiring member (210, 520) that electrically connects the second pad electrode (172) and the second antenna member.

[0309] [Supplementary Note 24] The terahertz device according to Supplementary Note 23, wherein the circuit member (160) includes a resistive element (221, 222) electrically connected between the first wiring member (200) and the second wiring member (210).

[0310] [Supplementary Note 25] The terahertz device according to Supplementary Note 24, wherein the circuit member (160) includes capacitors (181, 182) electrically connected between the first wiring member (200) and the second wiring member (210).

[0311] [Supplementary Note 26] The terahertz device according to Supplementary Note 25, wherein the capacitor includes a first capacitor (181) and a second capacitor (182) arranged on opposite sides of the antenna (150).

[0312] [Supplementary Note 27] The terahertz device according to Supplementary Note 26, wherein the resistive element includes: a first resistive element (221) disposed between the first pad electrode (171) and the first capacitor (181); and a second resistive element (222) disposed between the second pad electrode (172) and the second capacitor (182).

[0313] [Supplementary Note 28] The terahertz device according to any one of Supplementary Note 2 to Supplementary Note 22, wherein the circuit member (160, 500) includes a wiring member that connects the pad electrode and the antenna, and the curved portion (230) is provided on the wiring member.

[0314] [Supplementary Note 29] The terahertz device according to Supplementary Note 28, wherein widths (W41, W42) of the wiring member (160) are smaller than widths of the pad electrodes (W11, W12).

[0315] [Supplementary Note 30] The terahertz device according to Supplementary Note 28 or Supplementary Note 29, wherein the circuit member (160, 500) includes a fillet portion (316, 326) that widens from the wiring member (200, 210, 510, 520) toward the pad electrode (171, 172).

[0316] [Supplementary Note 31] The terahertz device according to any one of Supplementary Note 2 to Supplementary Note 22, wherein the circuit member (160) includes a capacitor (181, 182) electrically connected in parallel to the active element (130), and the curved portion (230) is provided at an end of an electrode plate (183, 184) constituting the capacitor.

[0317] [Supplementary Note 32] The terahertz device according to Supplementary Note 31, wherein the capacitor includes one or more corner portions (191 to 194), and the curved portion (230) is provided at the corner portion (191 to 194).

[0318] [Supplementary Note 33] The terahertz device according to Supplementary Note 32, wherein the capacitor includes a first corner portion and a second corner portion that is arranged closer to the active element (130, 450, 460) than the first corner portion, and the curved portion (230) is provided at the second corner portion.

[0319] [Supplementary Note 34] The terahertz device according to Supplementary Note 33, wherein the capacitor includes a third corner portion diagonally opposite the first corner portion and a fourth corner portion diagonally opposite the second corner portion, and the curved portion (230) is provided at the fourth corner portion.

[0320] [Supplementary Note 35] The terahertz device according to Supplementary Note 33, wherein the capacitor includes a third corner portion diagonally opposite the first corner portion and a fourth corner portion diagonally opposite the second corner portion, and the curved portion (230) is provided at the third corner portion.

[0321] [Supplementary Note 36] The terahertz device according to any one of Supplementary Note 31 to Supplementary Note 35, wherein the curved portion (230) has an arc shape that is convex outward.

[0322] [Supplementary Note 37] The terahertz device according to any one of Supplementary Note 31 to Supplementary Note 36, wherein the curved portion (230) is formed over at least half of the circumference of the capacitor, and the capacitor includes a portion that is semicircular in plan view.

[0323] [Supplementary Note 38] The terahertz device according to Supplementary Note 31, wherein the capacitor has a rectangular shape having four corners, and the curved portion (230) is provided at each of the four corners.

[0324] [Supplementary Note 39] The terahertz device according to Supplementary Note 38, wherein a side between two adjacent curved portions (230) is linear.

[0325] [Supplementary Note 40] The terahertz device according to Supplementary Note 38, wherein a side between two adjacent curved portions (230) is curved so as to be convex outward.

[0326] [Supplementary Note 41] The terahertz device according to Supplementary Note 40, wherein the radius of curvature of the curved portion (230) is smaller than the radius of curvature of the side.

[0327] [Supplementary Note 42] The terahertz device according to Supplementary Note 31, wherein the curved portion (230) is formed around the entire periphery of the capacitor, and the capacitor has a circular shape in the plan view.

[0328] [Supplementary Note 43] The terahertz device according to any one of Supplementary Note 31 to Supplementary Note 42, wherein the capacitor includes a first capacitor and a second capacitor arranged on either side of the antenna, and the first capacitor and the second capacitor have symmetrical shapes with respect to the antenna in the planar view.

[0329] [Supplementary Note 44] The terahertz device according to any one of Supplementary Note 31 to Supplementary Note 42, wherein the capacitor includes a first capacitor and a second capacitor arranged on either side of the antenna, and the first capacitor and the second capacitor have the same shape in the planar view.

[0330] [Supplementary Note 45] The terahertz device according to any one of Supplementary Note 31 to Supplementary Note 44, wherein the circuit member (500) includes: a wiring member (510, 520) that connects the pad electrodes (171, 172) and the antenna (400); and a resistive element (501, 502) that is electrically connected in parallel to the active element (450, 460).

[0331] [Appendix 46] The terahertz device according to Appendix 45, wherein the antenna (400) includes a first antenna member (410) and a second antenna member (420) with the active element (450, 460) electrically connected therebetween, the pad electrodes include: a first pad electrode (171) electrically connected to the first antenna member; and a second pad electrode (172) electrically connected to the second antenna member, the wiring members include: a first wiring member (510) electrically connecting the first pad electrode (171) and the first antenna member (410), and a second wiring member (520) electrically connecting the second pad electrode (172) and the second antenna member (420), and the resistive elements (501, 502) are electrically connected between the first antenna member (410) and the second antenna member (420).

[0332] [Supplementary Note 47] The terahertz device according to Supplementary Note 46, wherein the resistive element includes: a first resistive element (221) disposed between the first pad electrode (171) and the antenna (150); and a second resistive element (222) disposed between the second pad electrode (172) and the antenna (150).

[0333] [Supplementary Note 48] The terahertz device according to any one of Supplementary Note 2 to Supplementary Note 47, wherein the antenna is a dipole antenna.

[0334] [Supplementary Note 49] The terahertz device according to Supplementary Note 48, wherein the antenna (150) includes a first antenna member (151) and a second antenna member (152) extending in opposite directions from the active element (130).

[0335] [Supplementary Note 50] The terahertz device according to Supplementary Note 48 or Supplementary Note 49, wherein widths (W11, W12) of the pad electrodes (171, 172) are smaller than a length (L11) of the antenna (150).

[0336] [Supplementary Note 51] The terahertz device according to any one of Supplementary Note 2 to Supplementary Note 47, wherein the antenna is a slot antenna including a linear slot.

[0337] [Supplementary Note 52] The terahertz device according to any one of Supplementary Note 2 to Supplementary Note 47, wherein the antenna (400) is a slot antenna including an annular slot.

[0338] [Supplementary Note 53] The terahertz device according to Supplementary Note 52, comprising a conductive layer provided on a portion of the first surface (101), the conductive layer comprising: a first antenna member (410) partitioned by the slot; and a second antenna member (420) surrounding the first antenna member.

[0339] [Supplementary Note 54] The terahertz device according to Supplementary Note 53, wherein the active elements (450, 460) are provided in the slot and include a first active element (450) and a second active element (460) arranged on either side of the first antenna member (410) on a first reference line (LM) passing through the center of the first antenna member (410) in the planar view.

[0340] [Supplementary Note 55] The terahertz device according to Supplementary Note 54, comprising a first resistive element (501) and a second resistive element (502) electrically connected in parallel to the first active element (450) and the second active element (460).

[0341] [Supplementary Note 56] The terahertz device according to Supplementary Note 55, wherein the first resistive element (501) and the second resistive element (502) are arranged on a second reference line (LS) that passes through a center of the first antenna member (410) in the planar view and is perpendicular to a first reference line (LM).

[0342] [Supplementary Note 57] The terahertz device according to any one of Supplementary Note 1 to Supplementary Note 56, wherein the active element (130, 450, 460) includes any one of a resonant tunneling diode, a Tannett diode, an IMPATT diode, a GaAs-based field effect transistor, a GaN-based FET, a high electron mobility transistor, a heterojunction bipolar transistor, a CMOSFET, and an SBD.

[0343] The above description is merely illustrative. Those skilled in the art will recognize that many more possible combinations and permutations are possible other than the components and methods (manufacturing processes) listed for the purpose of illustrating the technology of the present disclosure. The present disclosure is intended to embrace all alternatives, modifications, and variations that fall within the scope of the present disclosure, including the claims.

[0344] 10, 10A to 10G... terahertz device, 20, 20A, 20B... terahertz device, 30, 30A, 30B... terahertz device, 40, 40A to 40F... terahertz device, 50... terahertz device, 60, 60A, 60B... terahertz device, 100... substrate, 101... substrate surface, 102... substrate back surface, 103 to 106... substrate side surface, 111 to 114... corners, 120... insulating layer, 121... insulating surface, 122... insulating back surface, 125... back metal layer, 126... reflective surface, 127... reflective back surface, 130... active element, 150... antenna, 151... first antenna member, 1 51A...tip, 151B...first antenna body, 151C...first connection portion, 152...second antenna member, 152A...tip, 152B...second antenna body, 152C...second connection portion, 160, 160A to 160G...circuit member, 171, 171A to 171E...first pad electrode, 172, 172A to 172E...second pad electrode, 181...first capacitor (capacitor), 182...second capacitor, 183...first electrode plate, 184...second electrode plate, 191 to 194...corner portion, 200, 200F...first wiring member, 201, 201F...first wiring portion, 20 2...second wiring portion, 203...third wiring portion, 204...via, 205...first wiring, 206...second wiring, 207...curved portion, 208...fillet portion, 210, 210F...second wiring member, 211, 211F...first wiring portion, 212...second wiring portion, 213...third wiring portion, 214...via, 215...first wiring, 216...second wiring, 217...curved portion, 218...fillet portion, 221...first resistor element (resistance element), 222...second resistor element, 230...curved portion, 231...portion, 240...conductive layer, 241...surface, 251-254...first to fourth sides, 261-264...corners Parts, 300, 300A, 300B...circuit member, 310...first wiring member, 311...first wiring portion, 312...second wiring portion, 313...first wiring, 314...second wiring, 315...curved portion, 316...fillet portion, 320...second wiring member, 321...first wiring portion, 322...second wiring portion, 323...first wiring, 324...second wiring, 325...curved portion, 326...fillet portion, 330...dummy pad electrode, 331...bump, 400...conductive layer, 401...slot, 402...ring slot antenna, 410...first antenna member, 411...center, 420, 420A,420B...second antenna member, 421 to 424...first to fourth sides, 425 to 428...first to fourth corner portions, 431 to 434...connection portions, 441, 442...virtual short-circuit points, 450...first active element, 500, 500C to 500E...circuit members, 501...first resistor element, 501A...first end portion, 501B...second end portion, 502...second resistor element, 502A...first end portion, 502B...second end portion, 510...first wiring member, 510C, 510D...first wiring member, 511...first wiring, 511D...first wiring portion, 512...via, 513...lower wiring, 51 4, 515... via, 516... first wiring, 517... second wiring, 518... curved portion, 519... fillet portion, 520... second wiring member, 520D, 520E... second wiring member, 521... first wiring, 521D, 521E... first wiring portion, 523... lower wiring, 524, 525... via, 526... first wiring, 527... second wiring, 528... curved portion, 529... fillet portion, 531... upper wiring, 532, 533... via, 534... insulating layer, 540... dummy pad electrode, 541... bump, LP... distance, P1... oscillation point, P2... radiation point, PA, PB... points,

Claims

1. A terahertz device comprising: a substrate including a first surface; an active element provided on the first surface for emitting or detecting electromagnetic waves; an antenna electrically connected to the active element; and a circuit member provided on the first surface and electrically connected to the antenna, wherein the circuit member includes a curved portion that is curved in a planar view viewed from a direction perpendicular to the first surface.

2. The terahertz device according to claim 1, wherein the circuit member includes a pad electrode used to apply a voltage to the active element or to transmit a signal detected by the active element, and the curved portion is provided at an end of the pad electrode.

3. The terahertz device according to claim 2, wherein the pad electrode includes one or more corner portions, and the curved portion is provided at the corner portion.

4. The terahertz device according to claim 2, wherein the pad electrode includes a first corner portion and a second corner portion that is positioned closer to the active element than the first corner portion, and the curved portion is provided at the second corner portion.

5. The terahertz device according to claim 4, wherein the pad electrode includes a third corner portion diagonally opposite the first corner portion and a fourth corner portion diagonally opposite the second corner portion, and the curved portion is provided at the fourth corner portion.

6. The terahertz device according to claim 4, wherein the pad electrode includes a third corner portion diagonally opposite the first corner portion and a fourth corner portion diagonally opposite the second corner portion, and the curved portion is provided at the third corner portion.

7. The terahertz device according to any one of claims 2 to 6, wherein the curved portion is arc-shaped so as to be convex outward.

8. A terahertz device according to any one of claims 2 to 7, wherein the curved portion is formed over at least half the circumference of the pad electrode, and the pad electrode includes a portion that is semicircular in plan view.

9. The terahertz device according to claim 2, wherein the pad electrode is rectangular with four corners, and the curved portion is provided at each of the four corners.

10. The terahertz device according to claim 2, wherein the curved portion is formed around the entire periphery of the pad electrode, and the pad electrode has a circular shape in the plan view.

11. The terahertz device according to any one of claims 2 to 10, wherein the pad electrodes include a first pad electrode and a second pad electrode electrically connected to the antenna.

12. The terahertz device according to claim 11, wherein the first pad electrode and the second pad electrode are arranged on either side of the antenna, and in the planar view, the first pad electrode and the second pad electrode are symmetrical with respect to the antenna.

13. The terahertz device according to claim 11, wherein the first pad electrode and the second pad electrode are arranged on either side of the antenna, and the first pad electrode and the second pad electrode have the same shape in the planar view.

14. A terahertz device according to any one of claims 11 to 13, wherein the first pad electrode and the second pad electrode are arranged in the center portions of two sides of the substrate that sandwich the antenna when viewed in the plane.

15. The terahertz device according to claim 11, wherein the first pad electrode and the second pad electrode are arranged at corners at both ends of one of two sides of the substrate that sandwich the antenna in the plan view.

16. The terahertz device according to claim 11, wherein the substrate has a rectangular shape including four corners in a plan view, the first pad electrode is disposed at one of the four corners, and the second pad electrode is disposed at a corner diagonally opposite the corner at which the first pad electrode is disposed.

17. A terahertz device according to any one of claims 11 to 16, wherein the substrate is rectangular in shape with four corners in the plan view, and includes dummy pad electrodes arranged at those of the four corners where no pad electrodes are arranged.

18. A terahertz device according to any one of claims 2 to 17, wherein the circuit member includes a wiring member that connects the pad electrode and the antenna, and the curved portion is provided on the wiring member.

19. A terahertz device according to any one of claims 2 to 17, wherein the circuit member includes a capacitor electrically connected in parallel to the active element, and the curved portion is provided at an end of an electrode plate that constitutes the capacitor.

20. The terahertz device according to claim 19, wherein the capacitor includes a first capacitor and a second capacitor arranged on either side of the antenna, and the first capacitor and the second capacitor are symmetrical with respect to the antenna in the plan view.

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