High-frequency FET

Abstract: On two active areas (13a, 13b) formed in a semiconductor substrate (12), source electrodes (14), gate electrodes (15), and drain electrodes (16) are disposed symmetrically to each other. A gate pad section (17) electrically connected to both gate electrodes (15) is disposed at one side of the active areas (13a, 13b), and a drain pad section (19) electrically connected to both drain electrodes (16) is disposed at the other side of the active areas (13a, 13b). A source pad section (19) electrically connected to one source electrode (14) is disposed at one side of the gate pad section (17) and the drain pad section (18), and a source pad section (19) electrically connected to the other source electrode (14) is disposed at the other side of the gate pad section (17) and the drain pad section (19). An input slot line (20) is formed between the gate pad section (17) and the source pad sections (19), and an output slot line (21) is formed between the drain pad section (18) and the source pad sections (19).

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to high-frequency semiconductor devices. The present invention more particularly relates to a high-frequency semiconductor device used for a millimetric-wave or quasi-millimetric-wave circuit module for amplification, oscillation, and modulation. 2. Description of the Related Art Fig. 1 is a plan showing a structure of a currently well used high-frequency semiconductor device (HEMT) 1. In this semiconductor device 1, on the upper surface of a compound semiconductor substrate 2 (width: 300 µm, length: 400 µm) in which two active areas 3a and 3b are formed, a drain pad section 4 is disposed at one side against the line connecting the active areas 3a and 3b, which serves as a boundary, two gate pad sections 8 are disposed at the other side, and a source pad section 6 is disposed around the gate pad sections 8. Drain electrodes 5 extend from the drain pad section 4 toward the active areas 3a and 3b, respectively. Source electrodes 7 each divided into two portions extend from the source pad section 6 to the active areas 3a and 3b, respectively. Gate electrodes 9 extend from the gate pad sections 8 toward the active areas 3a and 3b such that the gate electrodes pass between the two divided portions of the source electrodes 7. Each fine gate electrode 9 (having a gate length Lg of 0.15 µm) is disposed between the drain electrode 5 and the source electrode 7 in each of the active areas 3a and 3b. When this semiconductor device 1 is mounted to an external circuit board, the source electrodes 7 are connected to the ground of the circuit board with bonding wire connected to the source pad section 6, and the gate electrodes 9 and the drain electrodes 5 are connected to RF signal lines of the circuit board with bonding wire connected to the gate pad sections 8 and the drain pad section 4, respectively. An RF signal is input to the gate electrodes 9 from the circuit board through the bonding wire and output from the drain electrodes 5 to the circuit board through the bonding wire. In bonding wire through which an RF signal transmits, it is known that the RF characteristics of the semiconductor device 1 deteriorates due to the parasitic inductance of the bonding wire in high frequencies (especially in a millimetric wave). As understood from the structure of the semiconductor device 1 shown in Fig. 1, since the source electrodes 7 are disposed very close to the gate electrodes 9, parasitic capacitance exists between the gate electrodes 9 and the source electrodes 7. Due to parasitic capacitance between the gate electrodes 9 and the rear surface of the semiconductor substrate 2 in addition to the above parasitic capacitance, the high-frequency characteristics of the semiconductor device 1 deteriorate. To reduce parasitic components generated in a semiconductor device, flip-chip mounting using bumps may be employed instead of bonding wire. When flip-chip mounting with bumps is used, however, parasitic inductance caused by bonding wire decreases whereas parasitic capacitance between an electrode pad and a circuit board increases. This method does not essentially solve the problem. Since the drain pad section 4 is away from the source pad section 6 at the drain electrodes 5, parasitic capacitance between both pad sections 4 and 6 is small. Since the surface of the semiconductor is not covered by an electrode between the drain pad section 4 and the source pad section 6, however, a surface wave may be generated between both electrodes. It causes a loss and the RF characteristics deteriorate. As described above, a high-frequency semiconductor device having the conventional structure has a problem of source pad section 6, however, a surface wave may be generated between both electrodes. It causes a loss and the RF characteristics deteriorate. As described above, a high-frequency semiconductor device having the conventional structure has a problem of characteristics deterioration caused by parasitic components such as parasitic capacitance and inductance, and thereby yield in manufacturing semiconductor devices is reduced. It is very difficult to suppress the characteristics deterioration in a high-frequency semiconductor device having the conventional structure. JP-A-61 115 783 relates to a semiconductor device. The semiconductor device is provided with coplanar lines 14a and 14b having an equal characteristic impedance to that of a microwave measuring system. A gate electrode 4 and a drain electrode 3 of an intrinsic FET section 6 are connected, respectively, to the input and the output of a signal line 11 of the coplanar line 14. Source electrodes 2a and 2b are connected to a ground line 12 of the coplanar lines 14a and 14b. JP-A-63 164 504 describes a semiconductor device. A metal-semiconductor FET 4 is formed on the central part of a semiconductor substrate 1 made of GaAs. A gate electrode 5 is extended from a conductor 12 on the center of a operation layer 20. A drain electrode 6 and a source electrode 7 are connected to conductors 11, 13 so as to cover both operation layer 20 and substrate 1. Slot lines 31, 32 are formed by the conductors 11, 12 and 11, 13 and the lines 31, 32 are respectively used as an input terminal and an output terminal. SUMMARY OF THE INVENTION Starting from the above prior art, it is the object of the present invention to provide a high-frequency semiconductor device having reduced parasitic components and having improved high-frequency operational characteristics. This object is achieved by the high-frequency semiconductor device according to any one of independent claims 1 and 2. Specific embodiments are disclosed in the dependent claims. In the semiconductor device of the present invention active areas and electrodes are symmetrically disposed and connected in parallel in adjacent active areas. Therefore, since high-frequency signals output from adjacent active areas are combined in reverse phases, odd-number-order harmonics are suppressed. As a result, this harmonics suppression effect is great in power devices in which harmonics are generated substantially. Furthermore, since a high-frequency signal transfers through a slot line formed between the source pad section and the gate pad section or the drain pad section, parasitic inductance or parasitic capacitance is not generated between these pad sections or between electrodes unlike that in a conventional semiconductor device, and the semiconductor device achieves the maximum high-frequency characteristics which it inherently has. In addition in a semiconductor device according to the present invention, most areas other than slot lines are covered by the source pad sections, the gate pad section, and the drain pad section, the generation of a surface wave can be suppressed which is a problem in a millimetric-wave device. The high-frequency semiconductor device of the present invention may be configured such that a gate bias is applied to the center line of the gate pad section and a drain bias is applied to the center line of the drain pad section. In the high-frequency semiconductor device configured as described above, mutual interference between slot lines formed at both sides of the gate pad section and the drain pad section can be eliminated and signals having phases reverse to each other can be generated. It is necessary to determine the width of a slot line in a semiconductor device with input and output impedance matching being taken into consideration. Therefore, in an example high-frequency semiconductors device having the gate electrode with a gate length of 0.12 to 0.18 µm and a gate width of 40 to 80 µm, the widths of the slot lines range from 0.06 to 0.12 mm. Since the impedance of a circuit board is frequently set to 50 to 100 Ω, a millimetric-wave semiconductor device having a gate length of 0.12 to 0.18 µm and a gate width of 40 to 80 pm usually has an input impedance of 50 to 70 Ω and an output impedance of 70 to 90 Ω at 60 GHz. In this case, when the width of a slot line is set to 0.06 to 0.12 mm, input and output matching can be obtained at the entire semiconductor device and the reflection loss of a high-frequency signal can be made minimum. In some of the high-frequency semiconductor devices of the present invention, the source electrode and the source pad section change places with the drain electrode and the drain pad section, as compared with the other high-frequency semiconductor devices. In this way, a structure in which both electrodes and pad sections switch can be used. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a plan showing a structure of a conventional high-frequency semiconductor device. Fig. 2 is a plan showing a high-frequency semiconductor device according to an embodiment of the present invention. Fig. 3 is a partially-broken plan showing a condition in which the above semiconductor device is mounted on a circuit board. Fig. 4(a) is a chart indicating the waveform of an RF signal output from one active area; Fig. 4(b) is a chart indicating the waveform of an RF signal output from the other active area; and Fig. 4(c) is a chart indicating the waveform made by combing the waveform shown in Fig. 4(a) and the waveform shown in Fig. 4(b). Fig. 5 is a plan showing a high-frequency semiconductor device used in another embodiment of the present invention. Fig. 6 is a partially-broken plan showing a condition in which the above semiconductor device is mounted on a circuit board in said other embodiment of the present invention. Fig. 7 is a cross section taken on line X-X shown in Fig. 6. Fig. 8 is a plan showing a.high-frequency semiconductor device not part of the present invention. Fig. 9 is a plan showing a high-frequency semiconductor device used in yet another embodiment of the present invention. Fig. 10 is a cross section illustrating a condition in which the above semiconductor device is mounted on a circuit boar in said yet other embodiment of the present invention. Fig. 11 is a plan showing a high-frequency semiconductor device according to a further embodiment of the present invention. Fig. 12 is a plan showing a high-frequency semiconductor device according to a still further embodiment of the present invention. Fig. 13 is a plan showing a high-frequency semiconductor device used in a yet further embodiment of the present invention. DESCRIPTION OF THE PREFERRED EMBODIMENTS (First embodiment) Fig. 2 is a plan showing a structure of a high-frequency semiconductor device 11 according to one embodiment of the present invention. The device is used for amplification and oscillation. Two active areas 13a and 13b are formed in the front-surface layer of a semiconductor substrate 12 such as a semi-insulating GaAs substrate. As the semiconductor device 11, field effect transistors, such as an MESFET and an HEMT, and modified types thereof can be used. The two active areas 13a and 13b are disposed in parallel to the shorter sides of a device area in the semiconductor substrate 12. In both active areas 13a and 13b, source electrodes 14, gate electrodes 15, and drain electrodes 16 are formed from the outside. In other words, the electrodes 14 to 16 provided for both active areas 13a and 13b are symmetrically disposed, respectively. The gate electrodes 15 in both active areas 13a and 13b extend from a gate pad section 17 provided closer to the signal input side than the active areas 13a and 13b. The drain electrodes 16 in both active areas 13a and 13b extend from a drain pad section 18 provided closer to the signal output side than the active areas 13a and 13b. At both sides on the upper surface of the semiconductor substrate 12, source pad sections 19 are formed such that they sandwich the gate pad section 17 and the drain pad section 18, and the source electrodes 14 extend from the source pad sections 19. The input side of the semiconductor device 11 is formed by both source pad sections 19 and the gate pad section 17, and a Y-shaped, branched input slot line 20 is formed between the gate pad section 17 and the source pad sections 19. In the same way, the output side is formed by both source pad sections 19 and the drain pad section 18, and a Y-shaped, branched output slot line 21 is formed between the drain pad section 18 and the source pad sections 19. At positions which sandwich an end of the input slot line 20, via holes 22 electrically connected to the source pad sections 19 are formed in the semiconductor substrate 12. At positions which sandwich an end of the output slot line 21, via holes 23 electrically connected to the source pad sections 19 are formed in the semiconductor substrate 12. A via hole 24 electrically connected to the gate pad section 17 and a via hole 25 electrically connected to the drain pad section 18 are formed in the semiconductor substrate 12, and these via holes 24 and 25 are disposed at the center (on a short and long dotted line 26 shown in Fig. 2) of the gate pad section 17 and the drain pad section 18 such that both slot lines 20 and 21 operate in reverse-phase mode. An RF signal and a DC bias are applied to the via holes 22 and 23 electrically connected to the source electrodes 14, and DC biases are applied to the via holes 24 and 25 electrically connected to the gate electrode 15 and the drain electrode 16. The input and output slot lines 20 and 21 are designed such that their input and output impedances match those of FET sections (intrinsic device sections) formed at the active areas 13a and 13b. In other words, the slot width and the slot length of the slot lines 20 and 21 are designed such that the impedances of the slot lines 20 and 21 match those of the FET sections. Fig. 3 illustrates a condition in which the above-described high-frequency semiconductor device 11 is mounted on a circuit board 27 so that the device is used as an amplifier. On the upper surface of the circuit board 27, an input slot line 29 and an output slot line 30 are formed between ground conductors 28, and the input slot line 29 and the output slot line 30 are connected to an exposure surface 31 exposed from the ground conductors 28. A drain bias line 32 and a gate bias line 33 for applying DC biases against the ground conductors 28 are placed such that they divide the ground conductors 28. In the semiconductor device 11 mounted on the exposure surface 31 of the circuit board 27, the via holes 22 and 23 are connected to the ground conductors 28 at positions which sandwich the ends of the input and output slot lines 29 and 30 provided on the upper surface of the circuit board 27, and the slot lines 29 and 30 of the circuit board 27 are electrically connected to the slot lines 20 and 21 of the semiconductor device 11. The via hole 24 electrically connected to the center of the gate pad section 17 is connected to the gate bias line 33 of the circuit board 27, and the via hole 25 electrically connected to the center of the drain pad section 18 is connected to the drain bias line 32 of the circuit board 27. Thick arrows 34 shown in Fig. 3 indicate transfer conditions of an RF signal (electromagnetic wave) transferring from the slot line 29 of the circuit board 27 through the semiconductor device 11 to the slot line 30 of the circuit board 27. An RF signal transfers through the input slot line 29 formed in the circuit board 27, and enters the slot line 20 of the semiconductor device 11 through the via holes 22. The RF signal which has entered the slot line 20 of the semiconductor device 11 is divided into two portions in the slot line 20 and reaches the active areas 13a and 13b. When the RF signal reaches the source electrodes 14 and the gate electrodes 15 in the active areas 13a and 13b, it receives signal processing such as amplification through a mutual effect with a carrier in the active areas 13a and 13b, and output from the portions between the gate electrodes 15 and the drain electrodes 16 to the slot line 21. The RF signals output to the slot line 21 are combined at the junction of the slot line 21 and transferred to the slot line 30 of the circuit board 27 through the via holes 23. Therefore, an RF signal input to the input slot line 29 of the circuit board receives amplification operation and is output from the output slot line 30 of the circuit board 27. Features of the semiconductor device 11 according to the present embodiment will be described by comparing the device with the conventional semiconductor device. Since the conventional semiconductor device 1 is designed such that the gate pad sections 8 and the drain pad section 4 serve as electrodes in a lumped-constant circuit or electrodes having a microstripline structure, parasitic capacitance is generated between the gate pad sections 8 and the source pad section, and between the gate pad sections 8 and the drain pad section 4. In contrast in the semiconductor device 11 according to the present invention, since an RF signal transfers through the slot line 20 disposed between the gate pad section 17 and the source pad sections 19 and through the slot line 21 disposed between the drain pad section 18 and the source pad sections 19, parasitic capacitance does not exist. Since the input and output impedances of the slot lines 20 and 21 match those of the gate electrodes 15, an RF signal passes through the device inside without reflection. In the semiconductor device 11 according to the present embodiment, the gate pad section 17 and the drain pad section 18 are wide and the via holes 24 and 25 for DC biases are disposed at the centers of both pad sections 17 and 18. If the same structure is applied to the conventional semiconductor device 1, it is considered that parasitic capacitance increases and the impedance decreases so that input and output matching cannot be obtained. In the semiconductor device 11 according to the present invention, however, the width of the gate pad section 17 and the via holes 22 are required for preventing mutual interference between the two portions into which the slot line 20 branches, and the width of the drain pad section 18 and the via holes 23 are required for preventing mutual interference between the two portions into which the slot line 21 branches. Since an RF signal passes through the slot lines 20 and 21, and does not transfer through the gate electrodes 15 and the drain electrodes 16, the electrodes themselves do not cause parasitic capacitance. In the present embodiment, divided RF signals are in reverse phases with the source electrode 14 being taken as the reference, and amplified in the reverse phases and combined. Since RF signals passing through the two active areas 13a and 13b and transferring through the output slot line 21 are in phases reverse to each other, even-order harmonics are suppressed. More specifically, when the fundamental wave, the second harmonic wave, and the third harmonic wave shown in Fig. 4(a) are transferred from one active area, 13a, to the slot line 21, the fundamental wave, the second harmonic wave, and the third harmonic wave all having the reverse phase shown in Fig. 4(b) are transferred from the other active area, 13b, to the slot line 21. As a result of combining two waves having phases reverse to each other shown in Figs. 4(a) and 4(b), only the fundamental wave and the third harmonic wave, which are odd-order waves, remain and the second harmonic wave (even-order waves in general) is suppressed and vanishes. In a power device, in which harmonics are greatly generated, this suppression effect for harmonics is significant. When a power device operates in the B class, for example, the power efficiency of the device increases by 10% to 20%. As a result, a harmonics suppression circuit formed outside the device can be simplified. The dimensions of the semiconductor device 11 will be described below. The widths of the slot lines 20 and 21 formed in this high-frequency semiconductor device 11 are determined with input and output impedance matching being taken into consideration. The dimensions of the circuit board 27 or the device area are 400 µm in width and 600 µm in length. The impedance of the circuit board 27 is frequently set to 50 to 100 Ω. In a millimetric-wave semiconductor device having a gate length of 0.15 µm and a gate width of 50 µm, the input impedance Zi and the output impedance Zo of one gate electrode 15 are usually 50-70 Ω and 70-90 Ω at 60 GHz, respectively. In this case, when the widths of the slot lines 20 and 21 at portions indicated by A1 to A6 in Fig. 2 are set to 0.1 mm, 0.075 mm, 0.05 mm, 0.075 mm, 0.075 mm and 0.1 mm, input and output matching can be obtained for the entire semiconductor device 11, and the reflection loss of an RF signal is made minimum. The distances between the two portions of the slot lines at the positions indicated by A2 to A5 (namely, the widths D1 and D2 of the gate pad section 17 and the widths D3 and D4 of the drain pad section 18) in Fig. 2 must be 0.2 mm or more to prevent mutual interference of an RF signal between both slot lines 20 and 21 and to connect the gate bias line 33 and the drain bias line 32 through the vias holes 24 and 25. The thickness of the semiconductor substrate 12 is set to 0.05 to 0.13 mm (100 µm, for example) in order to reduce a connection loss of the slot lines 20 and 21 and to facilitate formation of via holes 22 to 25. (Second embodiment) Fig. 5 is a plan showing a structure of a high-frequency semiconductor device 41 used in a second embodiment of the present invention. This semiconductor device 41 is used for amplification, oscillation, and mixing. In this semiconductor device 41, slot lines are not divided, slot lines 20a and 20b are formed separately between a gate pad section 17 and source pad sections 19, and slot lines 21a and 21b are also formed separately between a drain pad section 18 and the source pad sections 19. The gate pad section 17 and the drain pad section 18 extend to ends of a semiconductor substrate 12 to align with the ends of the source pad sections 19, and via holes 42 and 43 are provided at ends of the gate pad section 17 and the drain pad section 18. Fig. 6 is a plan illustrating a condition in which the above-described high-frequency semiconductor device 41 is mounted on a circuit board 27 in said second embodiment of the present invention, and Fig. 7 is a cross section taken on line X-X shown in Fig. 6. Input and output slot lines 44 and 45 provided for the circuit board 27 branch in a Y shape. The semiconductor device 41 is mounted on the circuit board 27 such that the via holes 22 and 23 electrically connected to the source pad sections 19 are connected to the ground conductor 28 of the circuit board 27, the via hole 42 electrically connected to the gate pad section 17 is connected to the ground conductor 28 between the two portions into which the slot line 44 branches, of the circuit board 27, and the via hole 43 electrically connected to the drain pad section 18 is connected to the ground conductor 28 between the two portions into which the slot line 45 branches. The via hole 24 electrically connected to the gate pad section 17 is connected to a gate bias line 33, and the via hole 25 electrically connected to the drain pad section 18 is connected to a drain bias line 32. Therefore, the branch-type slot lines 44 and 45 provided for the circuit board 27 are connected to the slot lines 20a and 20b, and 21a and 21b of the semiconductor device 41, respectively. An RF signal (electromagnetic wave) transferring through the slot line 44 is divided into two portions on the circuit board 27, and input to the slot lines 20a and 20b of the semiconductor device 41. RF signals output from the slot lines 21a and 21b of the semiconductor device 41 transfer through the slot line 45 of the circuit board 27 and combined in the slot line 45 of the circuit board 27. When a half of the structure shown in Fig. 5 is separated and used, in said third embodiment of the present invention slot lines are made at the input and output sides even in a high-frequency semiconductor device having only one active area. Fig. 8 shows a high-frequency semiconductor device 46 having one active area 13 as described above. (Third embodiment) Fig. 9 is a plan showing a high-frequency semiconductor device 51 used in a third embodiment of the present invention. Fig. 10 is a cross section illustrating a condition in which the semiconductor device 51 is mounted on a circuit board 27. In this semiconductor device 51, source pad sections 19, a drain pad section 18, and a gate pad section 17 are provided with bumps 52, 53, 54, 55, 56, and 57 instead of via holes. When mounted on the same circuit board as the circuit board 27 shown in Fig. 6 in said third embodiment of the present invention, the semiconductor device 51 is flip-chip mounted on the circuit board 27 such that bumps 52 and 53 electrically connected to the source pad sections 19 are connected to the ground conductor 28 of the circuit board 27, a bump 54 electrically connected to the gate pad section 17 is connected to the ground . conductor 28 between the two portions of the slot line 44, of the circuit board 27, and a bump 55 electrically connected to the drain pad section 18 is connected to the ground conductor 28 between the two portions of the slot line 45. A bump 56 electrically connected to the gate pad section 17 is connected to the gate bias line 33, and a bump 57 electrically connected to the drain pad section 18 is connected to the drain bias line 32. The branch-type slot lines 44 and 45 provided for the circuit board 27 are connected to the slot lines 20a and 20b, and 21a and 21b of the semiconductor device 41 through the bumps 52 to 57. (Fourth embodiment) Fig. 11 is a plan showing a high-frequency semiconductor device 61 according to a further embodiment of the present invention. In this semiconductor device 61, slot lines 20 and 21 are divided twice, and thereby an RF signal input to the slot line 20 is transferred to four active areas 13a and 13b, and RF signals output from the four active areas 13a and 13b, are combined in the slot line 21 and output. In this semiconductor device 61, its output can be enlarged and even-order harmonics can be eliminated. (Fifth and sixth embodiments) In each high-frequency semiconductor device described in each of the above embodiments, the source electrodes 14 and the source pad sections 19 may change places with the drain electrodes 16 and the drain pad section 18. In this case, an input slot line 20 is formed between the drain pad section 18 and the gate pad section 17, and an output slot line 21 is formed between the drain pad section 18 and the source pad sections 19. Fig. 12 shows a high-frequency semiconductor device 62 in which the source electrodes 14 and the source pad section 19 change places with the drain electrodes 16 and the drain pad section 18, as compared with the device shown in Fig. 2. In Fig. 12, via holes 63 and 64 are electrically connected to the input and output sides of the drain pad sections 18, and connected to the ground conductor of a circuit board. A via hole 65 is electrically connected to the source pad section 19 and connected to a source bias line of the circuit board. Fig. 13 shows a high-frequency semiconductor device 66 in which the source electrodes 14 and the source pad sections 19 change places with the drain electrodes 16 and the drain pad section 18, as compared with the device Fig. 5 to be mounted on a circuit board 27 as shown in Fig 6. Also in these semiconductor devices 62 and 66 in which the source pad sections 19 change places with the drain pad section 18, improved characteristics are achieved in the same way as for the devices shown in Figs. 2 and 5.

Claims: A high-frequency semiconductor device comprising: a first and second adjacent active area (13a, 13b) formed in a semiconductor substrate (12), each having disposed therein a source electrode (14), a gate electrode (15) and a drain electrode (16), said source electrode (14), said gate electrode (15) and said drain electrode (16) of said first active area (13a) being disposed symmetrically to said source electrode (14), said gate electrode (15) and said drain electrode (16) of said second adjacent active area (13b), and each of said gate electrodes (15) being placed between one of said source electrodes (14) and one of said drain electrodes (16); a gate pad section (17) electrically connected to said gate electrodes (15) provided for said adjacent active areas (13a, 13b) disposed at an input region on said semiconductor substrate (12), and a drain pad section (18) electrically connected to said drain electrodes (16) provided for said adjacent active areas (13a, 13b) disposed at an output region on said semiconductor substrate (12); and source pad sections (19) electrically connected to said source electrodes (14) provided for said adjacent active areas (13a, 13b) disposed at both opposing sides along said gate pad section (17) and said drain pad section (18); wherein a first pair of slot lines (20a, 20b) is formed by said gate pad section (17) and said source pad sections (19), said first pair of slot lines (20a, 20b) forming said input region, and a second pair of slot lines (21a, 21b) is formed by said drain pad section (18) and said source pad sections (19), said second pair of slot lines (21a, 21b) forming said output region, characterised in that each slot line (20a, 20b) of said first pair of slot lines is electricallyconnected to a respective branch of a Y-shaped branched input slot line (20; 44), and each slot line (21a, 21b) of said second pair of slot lines is electrically connected to a respective branch of a Y-shaped branched output slot line (21; 45). A high-frequency semiconductor device comprising: a first and second adjacent active area (13a, 13b) formed in a semiconductor substrate (12), each having disposed therein a source electrode (14), a gate electrode (15) and a drain electrode (16), said source electrode (14), said gate electrode (15) and said drain electrode (16) of said first active area (13a) being disposed symmetrically to said source electrode (14), said gate electrode (15) and said drain electrode (16) of said adjacent second active area (13b), and each of said gate electrodes (15) being placed between one of said source electrodes (14) and one of said drain electrodes (16); a gate pad section (17) electrically connected to said gate electrodes (15) provided for said adjacent active areas (13a, 13b) disposed at an input region on said semiconductor substrate (12), and a source pad section (19) electrically connected to said source electrodes (14) provided for said adjacent active areas (13a, 13b) disposed at an output region on said semiconductor substrate (12); and drain pad sections (18) electrically connected to said drain electrodes (16) provided for said adjacent active areas (13a, 13b) disposed at both opposing sides along said gate pad section (17) and said source pad section (19) ; wherein a first pair of slot lines (20a, 20b) is formed by said gate pad section (17) and said drain pad sections (18), said first pair of slot lines (20a, 20b) forming said input region, and a second pair of slot lines (21a, 21b) is formed by said source pad section (19) and said drain pad sections (18), said second pair of slot lines (21a, 21b) forming said output region, characterised in that each slot line (20a, 20b) of said first pair of slot lines is electrically connected to a respective branch of a Y-shaped branched input slot line (20; 44), and each slot line (21a, 21b) of said second pair of slot lines is electrically connected to a respective branch of a Y-shaped branched output slot line (21; 45). A high-frequency semiconductor device according to Claim 1, wherein said gate pad section (17) is electrically connected to a gate bias line (33) to apply a gate bias to said gate electrode (15), and said drain pad section (18) is electrically connected to a drain bias line (32) to apply a drain bias to said drain electrode (16). A high-frequency semiconductor device according to Claim 2, wherein said gate pad section (17) is electrically connected to a gate bias line (33) to apply a gate bias to said gate electrode (15), and said source pad section (19) is electrically connected to a source bias line to apply a source bias to said source electrode (14). A high-frequency semiconductor device according to any one of Claims 1 to 4, wherein the widths of said slot lines (20a, 20b, 21a, 21b) range from 0.04 to 0.12 mm when each gate electrode (15) has a gate length of 0.12 to 0.18 µm and a gate width of 80 to 120 µm.

Inventors: ISHIKAWA YOHEI, SAKAMOTO KOICHI, ISHIKAWA, YOHEI, SAKAMOTO, KOICHI
Applicants: MURATA MANUFACTURING CO, MURATA MANUFACTURING CO., LTD.
Application year: 1997
Main classification: H01L29
IPC codes: H01L29, H01L21, H03F3