Compound semiconductor devices

Abstract: A field effect transistor includes a III-V compound semiconductor substrate (1) having a surface, III-V compound semiconductor layers successively disposed on said surface, including, from below, an InAlAs layer (5), an InP layer (6), and an InGaAs layer (7), a gate recess penetrating through the InGaAs layer (7) and the InP layer (6), and a gate electrode (8) in contact with the InAlAs layer (5). In this structure, the contact surface of the gate electrode (8) with the InAlAs layer (5) is on the same level with the interface between the InP layer (6) and the InAlAs layer (5). In producing the gate recess, the InGaAs layer (7) is first etched by an etchant comprising hydrogen peroxide water and at least one of tartaric acid, phosphoric acid, and sulfuric acid, using the InP layer (6) as an etching stopper layer, and then the InP layer (6) is etched by hydrochloric acid, using the InAlAs layer (5) as an etching stopper layer. Therefore, the depth of the gate recess is accurately determined by the etching stopper layers, resulting in field effect transistors with uniform electric characteristics.

Description: FIELD OF THE INVENTION The present invention relates to III-V compound semiconductor devices and, more particularly to field effect transistors comprising III-V compound semiconductors. BACKGROUND OF THE INVENTION In field effect transistors (hereinafter referred to as FETs), current flowing between source and drain electrodes is controlled by voltage applied to a gate electrode, that is, an input signal to the gate electrode is amplified and current equivalent to the signal amplified is output from the drain electrode. An FET in which electrons travel with high mobility through a two-dimensional electron gas layer is called a high electron mobility transistor (hereinafter referred to as HEMT), and the HEMT operates in a high frequency region of 40 GHz or more. Although the HEMT has a drawback in its low gate junction breakdown voltage, a HEMT with a recess structure achieves a gate junction breakdown voltage as high as that of a silicon device. Document JP-A-01166573 discloses a high electron mobility transistor (HEMT) using a field effect transistor including a laminated structure of III-V compound semiconductor layers. The structure consists of an InAlAs layer, an InP layer and an InGaAs layer laminated in this order on a GaInAs layer. A gate recess penetrates both through the InGaAs layer and the InP layer. Document JP-A-02295135 discloses a further transistor structure comprising two field effect transistors, wherein one FET also comprises a laminated structure of an InAlAs layer, an InP layer and an InGaAs layer laminated in this order on an InGaAs layer. However, also in this document the gate recess penetrates through both the InGaAs layer and the InP layer, thereby exposing the InAlAs layer. Figure 27 is a sectional view illustrating a conventional HEMT employing an InP substrate. In the figure, reference numeral 1 designates an InP substrate. An InAlAs buffer layer 2, an InGaAs channel layer 3, an n type InAlAs electron supply layer 4, an InAlAs Schottky junction formation layer 5, and an n type InGaAs ohmic contact layer 7 are successively disposed on the InP substrate 1. A gate recess penetrates the n type InGaAs ohmic contact layer 7 and reaches into the InAlAs Schottky junction formation layer 5, and a gate electrode 8 is disposed in the recess. A source electrode 9 and a drain electrode 10 are disposed on the n type InGaAs ohmic contact layer 7 spaced from each other. In this HEMT, current flows through the InGaAs channel layer 3 between the source and drain electrodes. This current is hereinafter referred to as drain current. Figure 29 is a sectional view illustrating a conventional MISFET (Metal Insulator Semiconductor FET) employing an InP substrate. In the figure, reference numeral 1 designates an InP substrate. An InAlAs buffer layer 2, an n type InGaAs channel layer 13, an InAlAs Schottky junction formation layer 5, and an n type InGaAs ohmic contact layer 7 are successively disposed on the InP substrate 1. A gate recess penetrates the n type InGaAs ohmic contact layer 7 and reaches into the InAlAs Schottky junction formation layer 5, and a gate electrode 8 is disposed in the recess. A source electrode 9 and a drain electrode 10 are disposed on the n type InGaAs ohmic contact layer 7 spaced from each other. In this MISFET, drain current flows through the n type InGaAs channel layer 13. Figure 30 is a sectional view illustrating a conventional HEMT employing a GaAs substrate. In the figure, reference numeral 14 designates a GaAs substrate. A GaAs buffer layer 15, an n type AlGaAs electron supply layer 16, an n type GaAs ohmic contact layer 17 are successively disposed on the GaAs substrate 14. A source electrode 9 and a drain electrode 10 are disposed on the n type GaAs ohmic contact layer 17 spaced from each other. In this HEMT, drain current flows through the GaAs buffer layer 15 in the vicinity of the boundary between the buffer layer 15 and the n type AlGaAs electron supply layer 16. Figure 31 is a sectional view illustrating a conventional MISFET employing a GaAs substrate. In the figure, reference numeral 14 designates a GaAs substrate. A GaAs buffer layer 15, an n type GaAs channel layer 18, an AlGaAs Schottky junction formation layer 19, and an n type GaAs ohmic contact layer 17 are successively disposed on the GaAs substrate 14. A gate recess penetrates the n type GaAs ohmic contact layer 17 and reaches into the AlGaAs Schottky junction formation layer 19, and a gate electrode 8 is disposed in the recess. A source electrode 9 and a drain electrode 10 are disposed on the n type GaAs ohmic contact layer 17 spaced from each other. In this MISFET, drain current flows through the n type GaAs channel layer 18. Figure 32 is a sectional view illustrating a conventional MESFET (Metal Semiconductor FET) employing a GaAs substrate. In the figure, reference numeral 14 designates a GaAs substrate. A GaAs buffer layer 15, an n type GaAs channel layer 18, an n type GaAs ohmic contact layer 17 are successively disposed on the GaAs substrate 14. A gate recess penetrates the n type GaAs ohmic contact layer 17 and reaches into the n type GaAs channel layer 18, and a gate electrode 8 is disposed in the recess. A source electrode 9 and a drain electrode 10 are disposed on the n type GaAs ohmic contact layer 17 spaced from each other. In this MESFET, drain current flows through the n type GaAs channel layer 18. Figures 28(a)-28(c) illustrate a method for producing the HEMT on the InP substrate shown in figure 27. Initially, on the InP substrate 1, the InAlAs buffer layer 2, the InGaAs channel layer 3, the n type InAlAs electron supply layer 4, the InAlAs Schottky junction formation layer 5, and the n type InGaAs ohmic contact layer 7 are successively grown by a crystal growth method (figure 28(a)). Then, the source and drain electrodes 9 and 10 are formed on the n type InGaAs ohmic contact layer 7 using vapor deposition and lift-off (figure 28(b)). Then, photoresist is deposited on the whole surface and patterned to form a photoresist mask 50. Then, portions of the n type InGaAs ohmic contact layer 7 and the InAlAs Schottky junction formation layer 5 are etched away using the photoresist mask 50, forming the gate recess (figure 28(c)). Then, a gate metal is deposited on the surface and the photoresist mask 50 and the overlying portions of the gate metal are removed by lift-off to form the gate electrode 8, resulting in the HEMT of figure 27. In the above-described FETs, the length of the channel, through which current flows from the source to drain, greatly influences electric characteristics of the FET, and the channel length is determined by the depth of the gate recess. Since the depth of the gate recess is usually calculated from the etching speed and the etching time, variations in the etching time directly cause variations in transistor characteristics. SUMMARY OF THE INVENTION It is an object of the present invention to provide field effect transistors with improved and uniform electric characteristics. According to the present invention this object is achieved by the measures indicated in claims 1, 2 and 4. The advantages of the invention will become apparent and obvious to those skilled in the pertinent art upon referring to the following description provided in connection with the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a cross-sectional view illustrating a semiconductor device in accordance with an example not forming part of the present invention; Figures 2(a)-2(d) are cross-sectional views illustrating a method for producing the semiconductor device of figure 1; Figure 3 is a cross-sectional view illustrating a semiconductor device in accordance with a further example not forming part of the present invention; Figure 4 is a cross-sectional view illustrating a semiconductor device in accordance with a further example not forming part of the present invention; Figure 5 is a cross-sectional view illustrating a semiconductor device in accordance with a first embodiment of the present invention; Figure 6 is a cross-sectional view illustrating a semiconductor device in accordance with a second embodiment of the present invention; Figure 7 is a cross-sectional view illustrating a semiconductor device in accordance with a third embodiment of the present invention; Figure 8 is a cross-sectional view illustrating a semiconductor device in accordance with a further example not forming part of the present invention; Figure 9 is a cross-sectional view illustrating a semiconductor device in accordance with a further example not forming part of the present invention; Figure 10 is a cross-sectional view illustrating a semiconductor device in accordance with a fifth embodiment of the present invention; Figure 11 is a cross-sectional view illustrating a semiconductor device in accordance with a further example not forming part of the present invention; Figure 12 is a cross-sectional view illustrating a semiconductor device in accordance with a fourth embodiment of the present invention; Figure 13 is a cross-sectional view illustrating a semiconductor device in accordance with a sixth embodiment of the present invention; Figure 14 is a cross-sectional view illustrating a semiconductor device in accordance with a seventh embodiment of the present invention; Figure 15 is a cross-sectional view illustrating a semiconductor device in accordance with an eighth embodiment of the present invention; Figure 16 is a cross-sectional view illustrating a semiconductor device in accordance with a ninth embodiment of the present invention; Figure 17 is a cross-sectional view illustrating a semiconductor device in accordance with a tenth embodiment of the present invention; Figure 18 is a cross-sectional view illustrating a semiconductor device in accordance with a eleventh embodiment of the present invention; Figure 19 is a cross-sectional view illustrating a semiconductor device in accordance with a twelfth embodiment of the present invention; Figure 20 is a cross-sectional view illustrating a semiconductor device in accordance with a further example not forming part of the present invention; Figure 21 is a cross-sectional view illustrating a semiconductor device in accordance with a thirteenth embodiment of the present invention; Figure 22 is a cross-sectional view illustrating a semiconductor device in accordance with a fourteenth embodiment of the present invention; Figure 23 is a cross-sectional view illustrating a semiconductor device in accordance with a fifteenth embodiment of the present invention; Figure 24 is a cross-sectional view illustrating a semiconductor device in accordance with an example not forming part of the present invention; Figure 25 is a cross-sectional view illustrating a semiconductor device in accordance with a sixteenth embodiment of the present invention; Figures 26(a)-26(c) are diagrams illustrating etching profiles of various etchants; Figure 27 is a cross-sectional view illustrating a HEMT using an InP substrate in accordance with the prior art; Figures 28(a)-28(c) are cross-sectional views illustrating a method for producing the HEMT of figure 27; Figure 29 is a cross-sectional view illustrating a MISFET utilizing an InP substrate in accordance with the prior art; Figure 30 is a cross-sectional view illustrating a HEMT utilizing a GaAs substrate in accordance with the prior art; Figure 31 is a cross-sectional view illustrating a MISFET utilizing a GaAs substrate in accordance with the prior art; Figure 32 is a cross-sectional view illustrating a MESFET utilizing a GaAs substrate in accordance with the prior art; DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Figure 1 is a cross-sectional view illustrating a HEMT employing an InP substrate in accordance with an example not forming part of the present invention. In figure 1, reference numeral 1 designates an InP substrate. An InAlAs buffer layer 2, an InGaAs channel layer 3, an n type InAlAs electron supply layer 4, and an InAlAs Schottky junction formation layer 5 are disposed on the InP substrate 1. A gate electrode 8 is disposed on the InAlAs Schottky junction formation layer 5. InP etching stopper layers 6 are disposed on the InAlAs Schottky junction formation layer 5 at opposite sides of the gate electrode 8. N type InGaAs ohmic contact layers 7 are disposed on the InP etching stopper layers 6. A source electrode 9 and a drain electrode 10 are disposed on the n type InGaAs ohmic contact layers 7 spaced from each other. A method for producing the HEMT of figure 1 is illustrated in figures 2(a)-2(d). Initially, there are successively grown on the InP substrate 1, the In 0.52 Al 0.48 As buffer layer 2 about 300 nm thick, the In 0.53 Ga 0.47 As channel layer 3 about 50 nm thick, the InAlAs electron supply layer 4 about 15 nm thick having a dopant concentration of about 4 x 10 18 cm -3 , the InAlAs Schottky junction formation layer 5 about 20 nm thick, the InP etching stopper layer 6 about 5 nm thick, the n type In 0.52 Ga 0.48 As ohmic contact layer 7 about 50 nm thick having a dopant concentration of about 4 x 10 18 cm -3 (figure 2(a)). Preferably, these layers are grown by MBE (Molecular Beam Epitaxy) or MOCVD (Metal Organic Chemical Vapor Deposition). Thereafter, source and drain electrodes 9 and 10 about 100 nm thick are formed on the n type InGaAs ohmic contact layer 7 by evaporation and lift-off. Preferably, the source and drain electrodes comprise Au/Ge/Ni, with Au in contact with the ohmic contact layer 7 (figure 2(b)). Then, a photoresist is deposited on the surface and patterned to form a photoresist mask 50, followed by a recess etching using the photoresist mask 50. The recess etching is carried out at 20 - 25°C using, as an etchant, a mixture of hydrogen peroxide water and at least one selected from tartaric acid, phosphoric acid, and sulfuric acid, which are mixed in the ratio of 1 : 50. During the etching, this etchant etches InGaAs as a III-V compound semiconductor including As as a main constituent of group V element but does not etch InP as a III-V compound semiconductor including P as a main constituent of group V element, so that the etching automatically stops when the bottom of the recess reaches the InP etching stopper layer 6 (figure 2(c)). The etching conditions described above are common to all embodiments of the present invention. Figures 26(a)-26(c) illustrate etching rates of the above-described three kinds of etchants to the InGaAs layer about 0.2 microns thick grown on the InP substrate. As shown in the figures, whichever etchant is used, it is possible to accurately stop the etching when the depth of the recess reaches 0.2 micron. After the recess etching, the InP etching stopper layer 6 exposed at the bottom of the recess is etched away using hydrochloric acid as shown in figure 2(d). It is well known that hydrochloric acid etches InP but does not etch InAlAs. Thereafter, a gate metal, such as aluminum, is deposited on the entire surface to a thickness of about 400 nm and the photoresist mask 50 and the overlying portions of the gate metal are removed by lift-off, forming a gate electrode in contact with the InAlAs Schottky junction formation layer 5. Thus, the HEMT shown in figure 1 is completed. According to this example not forming part of the present invention, the InGaAs and InAlAs layers as III-V compound semiconductor layers including As as a main constituent of group V element (hereinafter referred to as first compound semiconductor layers) and the InP layer as a III-V compound semiconductor layer including P as a main constituent of group V element (hereinafter referred to as second compound semiconductor) are laminated, and the recess etching is applied to the laminated structure using the etchant comprising hydrogen peroxide water and at least one of tartaric acid, phosphoric acid, and sulfuric acid, which etchant selectively etches the first compound semiconductor layers. Therefore, it is possible to accurately stop the etching at the surface of the second compound semiconductor layer, reducing variations in the depth of the recess. As the result, variations in electric characteristics of the HEMT are reduced. Figure 3 is a cross-sectional view illustrating a MISFET according to a further example not forming part of the present invention. In figure 3, the same reference numerals as in figure 1 designate the same parts. This MISFET includes an n type InGaAs channel layer 13 about 10 nm thick having a dopant concentration of about 1 x 10 18 cm -3 in place of the InGaAs channel layer 3 and the InAlAs electron supply layer 4 of figure 1. In all embodiments described hereinafter, layers beneath the etching stopper layer are grown by a crystal growth method, such as MBE, MOCVD, and the like, and layers designated by the same numeral have the same thicknesses and carrier concentrations. Figure 4 is a sectional view illustrating a HEMT employing an InP substrate in accordance with a further example not forming part of the present invention. In this example, a second InAlAs Schottky junction formation layer 11 about 10 nm thick and a second InP etching stopper layer 12 about 5 nm thick are inserted between the InP etching stopper layer 6 and the InGaAs ohmic contact layer 7. Therefore, the recess etching using the above-described etchant comprising hydrogen peroxide water and acid stops at the second InP etching stopper layer 12. Thereafter, the second etching stopper layer 12 exposed at the bottom of the recess is removed by hydrochloric acid, and the gate electrode 8 is formed on the second Schottky junction formation layer 11. Figure 5 is a cross-sectional view illustrating a HEMT employing an InP substrate in accordance with a first embodiment of the present invention. In this embodiment, after the recess etching shown in figure 2(c), the InP etching stopper layer 6 is not removed and the gate electrode 8 is formed on the InP etching stopper layer 6. Figure 6 is a cross-sectional view illustrating a MISFET employing an InP substrate in accordance with a second embodiment of the present invention. In this embodiment, after the recess etching using the above-described etchant comprising hydrogen peroxide water and acid, the InP etching stopper layer 6 is not removed and the gate electrode 8 is formed on the InP etching stopper layer 6. Figure 7 is a cross-sectional view illustrating a HEMT employing an InP substrate in accordance with a third embodiment of the present invention. In this embodiment, a second InAlAs Schottky junction formation layer 11 about 10 nm thick and a second InP etching stopper layer 12 about 5 nm thick are inserted between the InP etching stopper layer 6 and the InGaAs ohmic contact layer 7. Therefore, the recess etching using the etchant comprising hydrogen peroxide water and acid stops at the second InP etching stopper layer 12. Thereafter, the gate electrode 8 is formed on the second etching stopper layer 12. Figure 8 is a cross-sectional view illustrating a HEMT employing an InP substrate in accordance with a further example not forming part of the present invention. In this example, a second InAlAs Schottky junction formation layer 11 about 10 nm thick and a second InP etching stopper layer 12 about 5 nm thick are inserted between the InP etching stopper layer 6 and the InGaAs ohmic contact layer 7. Therefore, the recess etching using the etchant comprising hydrogen peroxide water and acid stops at the second InP etching stopper layer 12. Then, the second etching stopper layer 12 in the recess is removed by hydrochloric acid. Thereafter, the second InAlAs Schottky junction formation layer 11 and the InP etching stopper layer 6 are etched using the above-described etchants, and the gate electrode 8 is formed on the InAlAs Schottky junction formation layer 5. Figure 9 is a cross-sectional view illustrating a MISFET employing an InP substrate in accordance with a further example not forming part of the present invention. In figure 9, the same reference numerals as in figure 3 designate the same parts. This MISFET includes an n type InAlAs ohmic contact layer 70 about 50 nm thick having a dopant concentration of about 4 x 10 18 cm -3 in place of the n type InGaAs ohmic contact layer 7 of figure 1. The gate electrode 8 is formed after the InP etching stopper layer 6 in the recess is removed. Figure 11 is a cross-sectional view illustrating a HEMT employing an InP substrate in accordance with a further example not forming part of the present invention. In figure 11, the same reference numerals as in figure 1 designate the same parts. This HEMT includes an n type InAlAs ohmic contact layer 70 about 50 nm thick having a dopant concentration of about 4 x 10 18 cm -3 in place of the n type InGaAs ohmic contact layer 7 of figure 1. The gate electrode 8 is formed after the InP etching stopper layer 6 in the recess is removed. Figure 12 is a cross-sectional view illustrating a HEMT employing an InP substrate in accordance with an fourth embodiment of the present invention. In figure 12, the same reference numerals as in figure 8 designate the same parts. In this embodiment, after the recess etching using the etchant comprising hydrogen peroxide water and acid, the InP etching stopper layer 6 is not removed and the gate electrode 8 is formed on the InP etching stopper layer 6. Figure 10 is a cross-sectional view illustrating a MISFET employing an InP substrate in accordance with a fifth embodiment of the present invention. In the figure, the same reference numerals as in figure 3 designate the same parts. This MISFET includes an n type InAlAs ohmic contact layer 70 in place of the n type InGaAs ohmic contact layer 7 of figure 3. After the recess etching using the etchant comprising hydrogen peroxide water and acid, the InP etching stopper layer 6 in the recess is not removed and the gate electrode 8 is formed on the InP etching stopper layer 6. Figure 13 is a cross-sectional view illustrating a HEMT employing an InP substrate in accordance with a sixth embodiment of the present invention. In figure 13, the same reference numerals as in figure 11 designate the same parts. In this embodiment, after the recess etching using the etchant comprising hydrogen peroxide water and acid, the InP etching stopper layer 6 in the recess is not removed and the gate electrode 8 is formed on the InP etching stopper layer 6. Figure 14 is a cross-sectional view illustrating a semiconductor device comprising two HEMTs in accordance with a seventh embodiment of the present invention. In this embodiment, the HEMT of figure 1 and the HEMT of figure 5 are formed on the same substrate. In production, either of the two HEMTs may be formed first. Since the pinch-off voltage of the HEMT of figure 1 in which the InP etching stopper layer is absent beneath the gate is different from the pinch-off voltage of the HEMT of figure 5 in which the InP etching stopper layer is present beneath the gate. When these two transistors are combined on a substrate like complementary transistors, power consumption is reduced. In addition, since the number of transistors constituting a circuit is reduced, the circuit structure is simplified. In the HEMT of figure 1 with no InP layer 6 beneath the gate, the pinch-off occurs at a lower minus voltage than the HEMT of figure 5. Figure 16 is a cross-sectional view illustrating a semiconductor device comprising two MISFETs in accordance with a ninth embodiment of the present invention. In this embodiment, the MISFET of figure 3 and the MISFET of figure 6 are formed on the same substrate. Figure 17 is a cross-sectional view illustrating a semiconductor device comprising two HEMTs in accordance with a tenth embodiment of the present invention. In this embodiment, the HEMT of figure 4 and the HEMT of figure 7 are formed on the same substrate. Figure 18 is a cross-sectional view illustrating a semiconductor device comprising two HEMTs in accordance with a eleventh embodiment of the present invention. In this embodiment, the HEMT of figure 8 and the HEMT of figure 12 are formed on the same substrate. Figure 19 is a cross-sectional view illustrating a semiconductor device comprising two MISFETs in accordance with an twelfth embodiment of the present invention. In this embodiment, the MISFET of figure 9 and the MISFET of figure 10 are formed on the same substrate. Figure 15 is a cross-sectional view illustrating a semiconductor device comprising two HEMTs in accordance with a eighth embodiment of the present invention. In this embodiment, the HEMT of figure 11 and the HEMT of figure 13 are formed on the same substrate. Figure 20 is a cross-sectional view illustrating a semiconductor device comprising two HEMTs in accordance with a further example not forming part of the present invention. In this embodiment, the HEMT of figure 4 and the HEMT of figure 8 are formed on the same substrate. Figure 21 is a cross-sectional view illustrating a semiconductor device comprising two HEMTs in accordance with a thirteenth embodiment of the present invention. In this embodiment, the HEMT of figure 4 and the HEMT of figure 12 are formed on the same substrate. Figure 22 is a cross-sectional view illustrating a semiconductor device comprising two HEMTs in accordance with a fourteenth embodiment of the present invention. In this embodiment, the HEMT of figure 7 and the HEMT of figure 8 are formed on the same substrate. Figure 23 is a cross-sectional view illustrating a semiconductor device comprising two HEMTs in accordance with a fifteenth embodiment of the present invention. In this embodiment, the HEMT of figure 7 and the HEMT of figure 12 are formed on the same substrate. Figure 24 is a cross-sectional view illustrating a semiconductor device comprising two HEMTs in accordance with an example not forming part of the present invention. In this semiconductor device, a first InAlAs Schottky junction formation layer 5, a first InP etching stopper layer 6, a second InAlAs Schottky junction formation layer 11, and a second InP etching stopper layer 12 are successively disposed on the n type InAlAs electron supply layer 4. In producing the gate recesses of the two HEMTs 200a and 200b, first of all, prescribed portions of the n type InAlAs ohmic contact layer 19 are etched using the etchant comprising hydrogen peroxide water and at least one of tartaric acid, phosphoric acid, and sulfuric acid to expose the surface of the second InP etching stopper layer 12. Then, the second InP etching stopper layer 12 in the gate region of the HEMT 200a is removed to expose the second InAlAs Schottky junction formation layer 11, and the gate electrode 8a is formed on the second Schottky junction formation layer 11. Then, the second InAlAs Schottky junction formation layer 11 in the gate region of the HEMT 200b is etched using the above-described etchant to expose the surface of the first InP etching stopper layer 6. Then, the first InP etching stopper layer 6 in the gate region of the HEMT 200b is etched by hydrochloric acid to expose the surface of the first InAlAs Schottky junction formation layer 5, and the gate electrode 8b is formed on the first Schottky junction formation layer 5. Also in this case, either of the HEMTs 200a and 200b may be produced first. Figure 25 is a cross-sectional view illustrating a semiconductor device comprising two HEMTs in accordance with a sixteenth embodiment of the present invention. In the figure, the same reference numerals as in figure 24 designate the same parts. In producing gate recesses of the two HEMTs 300a and 300b, first of all, prescribed portions of the n type InAlAs ohmic contact layer 70 are etched using the above-described etchant comprising hydrogen peroxide water and acid to expose the surface of the second InP etching stopper layer 12. Then, the gate electrode 8a of the HEMT 300a is formed on the second InP etching stopper layer 12. Thereafter, the second InP etching stopper layer 12 and the second InAlAs Schottky junction formation layer 11 in the gate region of the HEMT 300b are etched away to expose the surface of the first InP etching stopper layer 6, and the gate electrode 8b of the HEMT 300b is formed on the first InP layer 6.

Claims: A field effect transistor including a plurality of III-V compound semiconductor layers successively disposed on a surface of a III-V compound semiconductor substrate (1), comprising a laminated structure comprising, from below, an InAlAs layer (5), an InP layer (6), and an InGaAs layer (7); a gate recess penetrating through said InGaAs layer (7); a gate electrode (8) formed in said gate recess being in contact with said InP layer (6); and the contact surface of said gate electrode (8) with said InP layer (6) being on the same level as the interface between said InGaAs layer (7) and said InP layer (6). A field effect transistor including a plurality of III-V compound semiconductor layers successively disposed on a surface of a III-V compound semiconductor substrate (1), comprising a laminated structure comprising a lower InAlAs layer (5), an InP layer (6), and an upper InAlAs layer (11); a gate recess penetrating through said upper InAlAs layer (11); a gate electrode (8) formed in said gate recess being in contact with said InP layer (6); and the contact surface of said gate electrode (8) with said InP layer (6) being on the same level as the interface between said upper InAlAs layer (11) and said InP layer (6). A semiconductor device comprising said field effect transistor of claim 1 and said field effect transistor of claim 2, formed on the same substrate. A semiconductor device including a plurality of III-V compound semiconductor layers successively disposed on a surface of a III-V compound semiconductor substrate (1), comprising a laminated structure comprising a lower InAlAs layer (5), a lower InP layer (6), an upper InAlAs layer (11), an upper InP layer (12) and a top InAlAs layer (70); a field effect transistor (300b) including a gate electrode (8b) formed in a recess and being in contact with said lower InP layer (6), the contact surface of said gate electrode (8b) with said lower InP layer (6) being on the same level as the interface between said upper InAlAs layer (11) and said lower InP layer (6); and a field effect transistor (300a) including a gate electrode (8a) formed in a recess and being in contact with said upper InP layer (12), the contact surface of said gate electrode (8a) with said upper InP layer (12) being on the same level as the interface between said top InAlAs layer (70) and said upper InP layer (12).

Inventors: NAKANISHI MASAHIKO, NAKANISHI, MASAHIKO, Nakanishi, Masahiko, c/o Mitsubishi Denki K.K.
Applicants: MITSUBISHI ELECTRIC CORP, MITSUBISHI DENKI KABUSHIKI KAISHA
Application year: 1993
Main classification: H01L29
IPC codes: H01L29, H01L21