Semiconductor laser device and method for manufacturing the same

Abstract

The semiconductor laser device (100) of the present disclosure comprises a semiconductor substrate (1), a first semiconductor layer (2) formed on the semiconductor substrate (1), an active layer (3) formed on the first semiconductor layer (2), a second semiconductor layer (4) formed on the active layer (3), a striped groove region (20a) formed on the surface side of the second semiconductor layer (4) along the optical waveguide direction and consisting of a plurality of striped grooves (20) extending in a direction perpendicular to the optical waveguide direction, and a surface electrode (10) formed on the surface of the second semiconductor layer (4) including the striped groove region (20a).

Description

[Technical Field]

[0001] The present disclosure relates to a semiconductor laser device and a method for manufacturing a semiconductor laser device. [Background technology]

[0002] A DFB laser (Distributed Feedback Laser) is a type of semiconductor laser characterized by its ability to oscillate in a single longitudinal mode (single wavelength). DFB lasers have an internal diffraction grating that selectively oscillates light of a specific wavelength. This allows DFB lasers to output laser light with a narrow spectral width and high frequency stability. DFB lasers are used as light sources in optical fiber communications. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 4462657 Summary of the Invention [Problem to be solved by the invention]

[0004] When narrowing the laser width of a DFB laser, if the DFB laser comes into direct contact with metal wiring with high thermal conductivity, the adhesion strength between the semiconductor layer and the metal decreases. On the other hand, an increase in the wiring length of the metal wiring due to contact with the metal wiring at a position away from the laser part of the DFB laser increases the electrical capacitance, which causes a problem of deteriorating high-speed response.

[0005] For example, the semiconductor light-emitting element disclosed in Patent Document 1 has grooves formed in the surface electrode for the purpose of heat dissipation, but as mentioned above, there is a problem in that when it comes into direct contact with metal wiring with high thermal conductivity, the adhesive strength between the semiconductor layer and the metal decreases.

[0006] The present disclosure has been made to solve the above-mentioned problems, and aims to provide a semiconductor laser device having a surface electrode with excellent adhesion to metal wiring, and a method for manufacturing a semiconductor laser device that can easily manufacture such a semiconductor laser device. [Means for solving the problem]

[0007] The semiconductor laser device according to the present disclosure comprises: a semiconductor substrate; a first semiconductor layer formed on the semiconductor substrate; an active layer formed on the first semiconductor layer; a second semiconductor layer formed on the active layer; a stripe-shaped groove region formed periodically along an optical waveguide direction on a surface side of the second semiconductor layer and consisting of a plurality of stripe-shaped grooves extending in a direction perpendicular to the optical waveguide direction; a diffraction grating layer provided inside the second semiconductor layer, the diffraction grating layer including a plurality of diffraction gratings periodically formed along the optical waveguide direction, at least a portion of which is positioned to face the plurality of stripe-shaped grooves; a surface electrode formed on the surface of the second semiconductor layer including the stripe-shaped groove region. 、 The period of the plurality of stripe-shaped grooves is set to be N times (1≦N≦6: N is a natural number) the period of the plurality of diffraction gratings. .

[0008] A method for manufacturing a semiconductor laser device according to the present disclosure includes: forming a first semiconductor layer, an active layer, a second semiconductor layer, and a diffraction grating layer inside the first semiconductor layer or the second semiconductor layer on a semiconductor substrate; forming an insulating film on a surface of the second semiconductor layer; periodically forming a plurality of stripe-shaped openings in the insulating film; forming a plurality of stripe-shaped grooves on the surface side of the second semiconductor layer by dry etching using the insulating film as a mask; and forming a surface electrode on the surface of the second semiconductor layer in a stripe-shaped groove region consisting of the plurality of stripe-shaped grooves, The diffraction grating layer is made up of a plurality of diffraction gratings periodically formed along the optical waveguide direction, and at least a portion of the diffraction gratings is positioned opposite the plurality of stripe-shaped grooves. and the period of the plurality of stripe-shaped grooves is set to be N times (1≦N≦6: N is a natural number) the period of the plurality of diffraction gratings. It is characterized by: [Effects of the Invention]

[0009] According to the semiconductor laser device of the present disclosure, a plurality of stripe-shaped grooves are formed in the semiconductor layer, and the stripe-shaped grooves are further covered with a surface electrode, thereby achieving the effect of obtaining a semiconductor laser device having a surface electrode with high adhesion strength to metal wiring.

[0010] The method for manufacturing a semiconductor laser device according to the present disclosure has the effect of easily manufacturing a semiconductor laser device having surface electrodes with high adhesive strength to metal wiring. [Brief explanation of the drawings]

[0011] [Figure 1] 1 is a top view of a semiconductor laser device according to a first embodiment. [Figure 2] 1 is a cross-sectional view taken along the optical waveguide direction of a semiconductor laser device according to a first embodiment. [Figure 3] 1 is a cross-sectional view taken along a direction perpendicular to the optical waveguide direction of a semiconductor laser device according to a first embodiment. [Figure 4] 1 is a schematic view of a semiconductor laser device according to a first embodiment. [Figure 5] 1A to 1C are schematic views illustrating a method for manufacturing a semiconductor laser device according to a first embodiment. [Figure 6] 1A to 1C are schematic views illustrating a method for manufacturing a semiconductor laser device according to a first embodiment. [Figure 7] 1A to 1C are schematic views illustrating a method for manufacturing a semiconductor laser device according to a first embodiment. [Figure 8] FIG. 10 is a top view of a semiconductor laser device according to a second embodiment. [Figure 9] FIG. 10 is a cross-sectional view taken along the optical waveguide direction of a semiconductor laser device according to a second embodiment. [Figure 10] FIG. 10 is a schematic view of a semiconductor laser device according to a second embodiment. [Figure 11] FIG. 10 is a top view of a semiconductor laser device according to a third embodiment. [Figure 12] FIG. 10 is a cross-sectional view taken along the optical waveguide direction of a semiconductor laser device according to a third embodiment. [Figure 13] FIG. 11 is a schematic view of a semiconductor laser device according to a third embodiment. [Figure 14] FIG. 10 is a top view of a semiconductor laser device according to a fourth embodiment. [Figure 15] FIG. 10 is a cross-sectional view taken along the optical waveguide direction of a semiconductor laser device according to a fourth embodiment. [Figure 16] FIG. 10 is a schematic view of a semiconductor laser device according to a fourth embodiment. [Figure 17] FIG. 11 is a top view of a semiconductor laser device according to a modification of the fourth embodiment. [Figure 18] FIG. 11 is a cross-sectional view taken along the optical waveguide direction of a semiconductor laser device according to a modification of the fourth embodiment. [Figure 19] FIG. 10 is a top view of a semiconductor laser device according to a fifth embodiment. [Figure 20] FIG. 10 is a cross-sectional view taken along the optical waveguide direction of a semiconductor laser device according to a fifth embodiment. [Figure 21] FIG. 10 is a schematic view of a semiconductor laser device according to a fifth embodiment. [Figure 22] 10A to 10C are cross-sectional views taken along the optical waveguide direction, illustrating a method for manufacturing a semiconductor laser device according to a fifth embodiment. [Figure 23] 10A to 10C are cross-sectional views taken along the optical waveguide direction, illustrating a method for manufacturing a semiconductor laser device according to a fifth embodiment. [Figure 24] 10A to 10C are cross-sectional views taken along the optical waveguide direction, illustrating a method for manufacturing a semiconductor laser device according to a fifth embodiment. [Figure 25] FIG. 13 is a top view of a semiconductor laser device according to a sixth embodiment. [Figure 26] FIG. 10 is a cross-sectional view taken along the optical waveguide direction of a semiconductor laser device according to a sixth embodiment. [Figure 27] FIG. 10 is a cross-sectional view taken along a direction perpendicular to the optical waveguide direction of a semiconductor laser device according to a sixth embodiment. [Figure 28] FIG. 13 is a schematic view of a semiconductor laser device according to a sixth embodiment. [Figure 29] 13 is a schematic view illustrating a method for manufacturing a semiconductor laser device according to a sixth embodiment. FIG. [Figure 30] 13 is a schematic view illustrating a method for manufacturing a semiconductor laser device according to a sixth embodiment. FIG. [Figure 31] 13 is a schematic view illustrating a method for manufacturing a semiconductor laser device according to a sixth embodiment. FIG. [Figure 32] FIG. 13 is a top view of a semiconductor laser device according to a seventh embodiment. [Figure 33] FIG. 11 is a cross-sectional view taken along the optical waveguide direction of a semiconductor laser device according to a seventh embodiment. [Figure 34] FIG. 11 is a cross-sectional view taken along a direction perpendicular to the optical waveguide direction of a semiconductor laser device according to a seventh embodiment. [Figure 35] FIG. 13 is a top view of a semiconductor laser device according to a modification of the seventh embodiment. [Figure 36] FIG. 13 is a cross-sectional view taken along the optical waveguide direction of a semiconductor laser device according to a modification of the seventh embodiment. [Figure 37] FIG. 13 is a cross-sectional view taken along a direction perpendicular to the optical waveguide direction of a semiconductor laser device according to a modification of the seventh embodiment. [Figure 38] FIG. 13 is a top view of a semiconductor laser device according to an eighth embodiment. [Figure 39] FIG. 13 is a cross-sectional view taken along a direction perpendicular to the optical waveguide direction of a semiconductor laser device according to an eighth embodiment. [Figure 40] FIG. 13 is a top view of a semiconductor laser device according to a ninth embodiment. [Figure 41] FIG. 13 is a cross-sectional view taken along a direction perpendicular to the optical waveguide direction of a semiconductor laser device according to a ninth embodiment. [Figure 42] FIG. 22 is a top view of a semiconductor laser device according to a tenth embodiment. [Figure 43]FIG. 22 is a cross-sectional view taken along a direction perpendicular to the optical waveguide direction of a semiconductor laser device according to a tenth embodiment. [Figure 44] FIG. 22 is a top view of a semiconductor laser device according to an eleventh embodiment. [Figure 45] FIG. 22 is a cross-sectional view taken along the optical waveguide direction of a semiconductor laser device according to an eleventh embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0012] Embodiment 1 Fig. 1 is a top view of a semiconductor laser device 100 according to the first embodiment. Fig. 2 is a cross-sectional view taken along the optical waveguide direction of the semiconductor laser device 100 according to the first embodiment, i.e., line A-A' in Fig. 1. Fig. 3 is a cross-sectional view taken along a direction perpendicular to the optical waveguide direction of the semiconductor laser device 100 according to the first embodiment, i.e., line B-B' in Fig. 1. Fig. 4 is a schematic view of the semiconductor laser device 100 according to the first embodiment.

[0013] <Element structure of semiconductor laser device according to first embodiment> The semiconductor laser device 100 according to the first embodiment includes a semiconductor substrate 1, a first semiconductor layer 2, an active layer 3 that emits laser light, a second semiconductor layer 4, a diffraction grating layer 5 formed inside the second semiconductor layer 4, a striped groove region 20a formed on the surface side of the second semiconductor layer 4 along the optical waveguide direction of the laser light and consisting of a plurality of striped grooves 20 extending in a direction perpendicular to the optical waveguide direction, a surface electrode 10 formed on the surface of the second semiconductor layer 4 including the striped groove region 20a, and a back electrode 11 formed on the back side of the semiconductor substrate 1.

[0014] As shown in the cross-sectional view of Fig. 3, current blocking layers 6 are formed on both side surfaces of the mesa structure 15 including the active layer 3. Furthermore, as shown in the schematic view of Fig. 4, metal wiring 35 is provided on the surface electrode 10 including the stripe-shaped groove region 20a.

[0015] The first semiconductor layer 2 and the second semiconductor layer 4 function as cladding layers. The first semiconductor layer 2 and the second semiconductor layer 4 are made of, for example, indium phosphide (InP) or gallium arsenide (GaAs).

[0016] The active layer 3 has a quantum well structure made of elements such as indium (In), gallium (Ga), phosphorus (P), arsenic (As), and aluminum (Al). The diffraction grating layer 5 has a plurality of diffraction gratings 5a made of a semiconductor having a refractive index different from that of the material making up the second semiconductor layer 4, which are periodically arranged along the optical waveguide direction.

[0017] The current blocking layers 6 provided on both sides of the mesa structure 15 including the active layer 3 may be made of an insulating semiconductor layer or may be made of a thyristor structure.

[0018] A reflective film 30a and a reflective film 30b are provided on the output end face and the rear end face of the semiconductor laser device 100, respectively. The reflective film 30a and the reflective film 30b are made of, for example, an insulating film. However, the reflective film 30a and the reflective film 30b may be made of a metal film. When the reflective film 30a and the reflective film 30b are made of a metal film, it is desirable to provide an insulating film or an insulating semiconductor layer between the surface electrode 10 and the reflective film 30a and the reflective film 30b, respectively, to prevent the surface electrode 10 from contacting the reflective film 30a and the reflective film 30b.

[0019] Specific examples of the surface electrode 10 include a single layer or laminated structure of gold (Au), platinum (Pt), titanium (Ti), niobium (Nb), nickel (Ni), Al, or an alloy made of these metals.

[0020] Examples of metal materials constituting the metal wiring 35 include solder alloys, and metals such as Au, silver (Ag), copper (Cu), Pt, zinc (Zn), and Ni. In particular, when the metal wiring 35 made of a metal material different from that of the surface electrode 10 is attached to the surface electrode 10, a stronger wiring adhesion can be achieved compared to when both are made of the same metal material.

[0021] <Features of the semiconductor laser device according to the first embodiment> In the semiconductor laser device 100 according to the first embodiment, a stripe-shaped groove region 20a is provided in a part of the surface side of the second semiconductor layer 4, the stripe-shaped groove region 20a being formed along the optical waveguide direction of the laser light and consisting of a plurality of stripe-shaped grooves 20 extending in a direction perpendicular to the optical waveguide direction. Furthermore, a surface electrode 10 is formed on the surface of the second semiconductor layer 4 including the stripe-shaped grooves 20. In other words, both side surfaces and the bottom surface of the stripe-shaped groove 20 are covered with the surface electrode 10. Furthermore, the plurality of stripe-shaped grooves 20 may be formed periodically along the optical waveguide direction.

[0022] The diffraction grating layer 5 is provided inside the second semiconductor layer 4 and is composed of a plurality of diffraction gratings 5a that are periodically formed in the optical waveguide direction. Furthermore, at least some of the plurality of diffraction gratings 5a are positioned opposite the plurality of stripe-shaped grooves 20.

[0023] The metal wiring 35 is bonded to the surface electrode 10 so as to include the surface electrode 10 formed so as to cover the plurality of stripe-shaped grooves 20. By providing the plurality of stripe-shaped grooves 20, the contact area between the metal wiring 35 and the surface electrode 10 increases, which has the effect of improving the adhesion of the metal wiring 35 to the surface electrode 10.

[0024] The aspect ratio of the stripe-shaped grooves 20, that is, the ratio of the depth of the stripe-shaped grooves to the opening width of the stripe-shaped grooves, is preferably within the range of 1 to 20. In particular, in the case of the second semiconductor layer 4 containing In, the shape of the stripe-shaped grooves 20 with a higher aspect ratio can be realized by using, for example, hydrogen iodide with the insulating film pattern as a mask.

[0025] <Method of Manufacturing Semiconductor Laser Device According to First Embodiment> The following describes characteristic manufacturing steps in the method for manufacturing the semiconductor laser device 100 according to the first embodiment. Figures 5 to 7 are overviews showing the manufacturing method for the semiconductor laser device according to the first embodiment.

[0026] First, a first semiconductor layer 2, an active layer 3, a second semiconductor layer 4, and a diffraction grating layer 5 are formed inside the second semiconductor layer 4 on a semiconductor substrate 1. Fig. 5 is a schematic view after the layers have been formed.

[0027] The diffraction grating layer 5 is formed by RIE (Reactive Ion Etching) using methane, hydrogen, chlorine, silicon tetrachloride, boron trichloride, hydrogen iodide, etc. The diffraction grating layer 5 may also be formed by selective wet etching using an acid or alkaline solution.

[0028] An insulating film is formed on the surface of the second semiconductor layer 4 by CVD (Chemical Vapor Deposition) or other methods, and multiple stripe-shaped openings are periodically formed in this insulating film. Using this insulating film as a mask, multiple stripe-shaped grooves 20 are formed on the surface side of the second semiconductor layer 4 by RIE using, for example, a gas containing chlorine atoms such as methane, hydrogen, chlorine, silicon tetrachloride, or boron trichloride, or a gas containing iodine atoms such as hydrogen iodide. Etching can be stopped, for example, by utilizing the processing selectivity between semiconductors, or by spectroscopic detection using plasma spectroscopy or interference spectroscopy. Figure 6 shows an overview after the stripe-shaped grooves 20 have been formed.

[0029] The insulating film constituting the patterning mask may be, for example, a silicon oxide film (SiO), a silicon nitride film (SiN), a silicon oxynitride film (SiON), etc. Instead of an insulating film, a resist film may also be used.

[0030] A front surface electrode 10 is formed on the surface of the second semiconductor layer 4 in a portion including the plurality of stripe-shaped grooves 20. Fig. 7 is a schematic view of the front surface electrode 10 after it has been formed. The front surface electrode 10 is formed by a method such as sputtering, vapor deposition, or plating.

[0031] <Advantages of First Embodiment> As described above, according to the semiconductor laser device of embodiment 1, a plurality of stripe-shaped grooves are provided on the surface side of the second semiconductor layer, and further, a surface electrode is provided so as to cover the plurality of stripe-shaped grooves. This increases the contact area between the metal wiring and the surface electrode, thereby achieving the effect of obtaining a semiconductor laser device with improved adhesion of the metal wiring to the surface electrode.

[0032] As described above, the method for manufacturing a semiconductor laser device according to the first embodiment has the effect of easily manufacturing a semiconductor laser device in which the adhesive strength of the metal wiring to the surface electrode is improved.

[0033] Embodiment 2 Fig. 8 is a top view of a semiconductor laser device 110 according to the second embodiment. Fig. 9 is a cross-sectional view of the semiconductor laser device 110 according to the second embodiment in the optical waveguide direction, that is, taken along line A-A' in Fig. 8. Fig. 10 is a schematic view of the semiconductor laser device 110 according to the second embodiment.

[0034] <Element structure of semiconductor laser device according to second embodiment> The semiconductor laser device 110 according to the second embodiment is structurally different from the semiconductor laser device 100 according to the first embodiment in that the semiconductor laser device 110 according to the second embodiment has a contact layer 7 between the second semiconductor layer 4 and the surface electrode 10.

[0035] The contact layer 7 is made of, for example, indium gallium arsenide (InGaAs) or indium gallium arsenide phosphide (InGaAsP) which is made of three or more elements. The contact layer 7 may be formed on the entire surface of the second semiconductor layer 4, or may be formed on only a part of the surface of the second semiconductor layer 4. In the example of the device structure shown in FIG. 8, the contact layer 7 is formed on the entire surface of the second semiconductor layer 4.

[0036] The contact layer 7 is provided to facilitate current injection into the active layer 3 and to achieve high efficiency. In other words, providing the contact layer 7 reduces the contact resistance between the surface electrode 10 and the semiconductor layer, thereby achieving low resistance in the semiconductor laser device 110. As a result, high efficiency in the semiconductor laser device 110 is possible.

[0037] <Advantages of the Second Embodiment> As described above, according to the semiconductor laser device of embodiment 2, a contact layer is further provided between the second semiconductor layer and the surface electrode in the element structure of the semiconductor laser device of embodiment 1, and therefore, in addition to the effect of embodiment 1, an effect is achieved in that a semiconductor laser device that can achieve higher efficiency is obtained.

[0038] Embodiment 3 Fig. 11 is a top view of a semiconductor laser device 120 according to the third embodiment. Fig. 12 is a cross-sectional view of the semiconductor laser device 120 according to the third embodiment in the optical waveguide direction, i.e., taken along line A-A' in Fig. 11. Fig. 13 is a schematic view of the semiconductor laser device 120 according to the third embodiment.

[0039] <Element structure of semiconductor laser device according to third embodiment> The semiconductor laser device 120 according to the third embodiment has the same semiconductor layer configuration as the semiconductor laser device 100 according to the first embodiment or the semiconductor laser device 110 according to the second embodiment. The semiconductor laser device 120 according to the third embodiment is characterized in that the period of the plurality of stripe-shaped grooves 20 is the same as the period of the plurality of diffraction gratings 5a that constitute the diffraction grating layer 5.

[0040] In the semiconductor laser device 120 according to the third embodiment, the diffraction grating layer 5 and the stripe-shaped groove region 20a are arranged such that the bottom surface of each stripe-shaped groove 20 faces the upper surface of the diffraction grating 5a. By adopting such a configuration, the laser light guided within the active layer 3 senses the refractive index difference on the stripe-shaped groove 20 side, which has the effect of facilitating the laser light to be in a single mode.

[0041] The width of the bottom surface of the stripe-shaped groove 20 in the optical waveguide direction may be set to be the same as the width of the diffraction grating 5a in the optical waveguide direction, or may be set to be larger than the width of the diffraction grating 5a in the optical waveguide direction.

[0042] Furthermore, the period of the plurality of stripe-shaped grooves 20 may be set to be N times (2≦N≦6: N is a natural number) the period of the plurality of diffraction gratings 5a.

[0043] In addition to the effects achieved by the semiconductor laser device 100 according to the first embodiment or the semiconductor laser device 110 according to the second embodiment, the semiconductor laser device 120 according to the third embodiment can effectively increase the voltage applied to the diffraction grating layer 5, which is normally highly resistive, by utilizing the fact that the thickness of the second semiconductor layer 4 at the bottom of the stripe-shaped groove 20 is relatively small. As a result, the semiconductor laser device 120 according to the third embodiment can reduce power consumption during laser output. In other words, it is possible to obtain optical output equivalent to that of a normal laser with low power consumption.

[0044] <Advantages of the Third Embodiment> As described above, the semiconductor laser device according to the third embodiment further includes the same element structure as the semiconductor laser device according to the first embodiment or the semiconductor laser device according to the second embodiment, in which the period of the plurality of stripe-shaped grooves and the period of the plurality of diffraction gratings constituting the diffraction grating layer are set to be the same, for example. This provides the effect of obtaining a semiconductor laser device with reduced power consumption in addition to the effect of the first or second embodiment.

[0045] Embodiment 4 Fig. 14 is a top view of a semiconductor laser device 130 according to the fourth embodiment. Fig. 15 is a cross-sectional view of the semiconductor laser device 130 according to the fourth embodiment in the optical waveguide direction, i.e., taken along line A-A' in Fig. 14. Fig. 16 is a schematic view of the semiconductor laser device 130 according to the fourth embodiment.

[0046] <Element structure of semiconductor laser device according to embodiment 4> The semiconductor laser device 130 according to the fourth embodiment has the same semiconductor layer configuration as the semiconductor laser device 120 according to the third embodiment. In the semiconductor laser device 120 according to the third embodiment, the diffraction grating layer 5 and the striped groove region 20a are opposed to each other such that the bottom surface of each striped groove 20 faces the upper surface of the diffraction grating 5a, whereas the semiconductor laser device 130 according to the fourth embodiment is characterized in that the diffraction grating layer 5 and the striped groove region 20a are opposed to each other such that the protrusions 22 between each striped groove 20 face the upper surface of the diffraction grating 5a.

[0047] The period of the plurality of stripe-shaped grooves 20 may be set to be N times (2≦N≦6: N is a natural number) the period of the plurality of diffraction gratings 5a.

[0048] In addition to the effects of the first or second embodiment, the semiconductor laser device 130 according to the fourth embodiment can enhance the diffraction effect of the diffraction grating layer 5 due to the refractive index of air or vacuum resulting from the provision of the stripe-shaped grooves 20, and therefore can output single-phase laser light even at high power output.

[0049] Even if the thickness of the second semiconductor layer 4 cannot be reduced due to flattening of the buried portion during epitaxial crystal growth or other reasons, it is possible to reduce the resistance of the semiconductor laser device 130, i.e., reduce power consumption.

[0050] <Advantages of the Fourth Embodiment> As described above, the semiconductor laser device according to the fourth embodiment further includes the same element structure as the semiconductor laser device according to the first embodiment or the semiconductor laser device according to the second embodiment, in which the convex portions between the stripe-shaped grooves are positioned to face the upper surface of the diffraction grating. This provides the effect of obtaining a semiconductor laser device that can output single-phase laser light even at high output power, in addition to the effect of the first or second embodiment.

[0051] A variation of the fourth embodiment. Fig. 17 is a top view of a semiconductor laser device 135 according to a modification of the fourth embodiment. Fig. 18 is a cross-sectional view taken along the optical waveguide direction of a semiconductor laser device 130 according to a modification of the fourth embodiment, that is, along the line A-A' in Fig. 17.

[0052] <Element structure of semiconductor laser device according to a modification of the fourth embodiment> The semiconductor laser device 135 according to the modification of the fourth embodiment has the same semiconductor layer configuration as the semiconductor laser device 130 according to the fourth embodiment. The semiconductor laser device 135 according to the modification of the fourth embodiment is characterized in that the width in the optical waveguide direction of the convex portions 22 between the stripe-shaped grooves 20 is smaller than the width in the optical waveguide direction of the upper surface of the diffraction grating 5a.

[0053] <Effects of the Modification of the Fourth Embodiment> As described above, according to the semiconductor laser device of the modified example of the fourth embodiment, in addition to the element structure of the semiconductor laser device of the fourth embodiment, the width of the convex portions between the stripe-shaped grooves in the optical waveguide direction is arranged to be smaller than the width of the upper surface of the diffraction grating in the optical waveguide direction. This provides an effect of obtaining a semiconductor laser device with lower power consumption in addition to the effect of the first or second embodiment.

[0054] Embodiment 5. Fig. 19 is a top view of a semiconductor laser device 140 according to the fifth embodiment. Fig. 20 is a cross-sectional view of the semiconductor laser device 140 according to the fifth embodiment in the optical waveguide direction, that is, taken along line A-A' in Fig. 19. Fig. 21 is a schematic view of the semiconductor laser device 140 according to the fifth embodiment.

[0055] <Element structure of semiconductor laser device according to embodiment 5> The semiconductor laser device 140 according to the fifth embodiment is the same as the semiconductor laser device 120 according to the third embodiment in terms of the configuration of the semiconductor layer, the arrangement of the stripe-shaped grooves 20, etc. On the other hand, the semiconductor laser device 140 according to the fifth embodiment is characterized in that it has an insulating film 40 provided between the second semiconductor layer 4 and the surface electrode 10 in at least a part of the region where the surface electrode 10 is formed.

[0056] Forming the insulating film 40 between the second semiconductor layer 4 and the front surface electrode 10 makes it possible to inject current into any region of the semiconductor laser device. This is because the region where the insulating film 40 is formed is electrically insulated by the insulating film 40, and no current flows through it, even if the front surface electrode 10 is formed on the surface of the insulating film 40. Note that the stripe-shaped grooves 20 may be located below the insulating film 40, but it is more preferable that the stripe-shaped grooves 20 are not present. Furthermore, the front surface electrode 10 does not have to be provided on the insulating film 40.

[0057] <Method of Manufacturing Semiconductor Laser Device According to Fifth Embodiment> The following describes characteristic manufacturing steps in the manufacturing method of the semiconductor laser device 140 according to the fifth embodiment. Figures 22 to 24 are cross-sectional views taken along the optical waveguide direction, illustrating the manufacturing method of the semiconductor laser device 140 according to the fifth embodiment.

[0058] After forming a first semiconductor layer 2, an active layer 3, a second semiconductor layer 4, and a diffraction grating layer 5 inside the second semiconductor layer 4 on the surface of the semiconductor substrate 1, an insulating film 40a is formed by a CVD method or the like on the surface of the second semiconductor layer 4. A plurality of stripe-shaped openings corresponding to the plurality of stripe-shaped grooves 20, i.e., a stripe pattern, are periodically formed in part of this insulating film 40a.

[0059] Using this insulating film 40a as a mask, a plurality of stripe-shaped grooves 20 are periodically formed by dry etching such as RIE on the surface side of the second semiconductor layer 4. Fig. 22 is a cross-sectional view taken along the optical waveguide direction after the stripe-shaped grooves 20 have been formed.

[0060] The region where the insulating film is to remain is covered with a resist film 41, and using the resist film 41 as a mask, the insulating film not covered by the resist film 41 is removed by wet etching using hydrofluoric acid as an etchant. Figure 23 is a cross-sectional view along the optical waveguide direction after the unnecessary insulating film has been removed.

[0061] A metal film constituting the surface electrode 10 is formed by a method such as sputtering, vapor deposition, or plating on the surface of the second semiconductor layer 4, which includes the plurality of stripe-shaped grooves 20. Then, the resist film 41 is removed to form an insulating film 40 covering a part of the second semiconductor layer 4, as shown in FIG.

[0062] <Advantages of the Fifth Embodiment> As described above, the semiconductor laser device according to embodiment 5 has the same element structure as the semiconductor laser device according to embodiment 1 or 2, but further includes an insulating film on the surface of the second semiconductor layer in at least a part of the region where the surface electrode is formed. This provides the effect of obtaining a semiconductor laser device that allows current injection in any region, in addition to the effect of embodiment 1 or 2.

[0063] Embodiment 6 Fig. 25 is a top view of a semiconductor laser device 150 according to the sixth embodiment. Fig. 26 is a cross-sectional view taken along the optical waveguide direction of the semiconductor laser device 150 according to the sixth embodiment, i.e., line A-A' in Fig. 25. Fig. 27 is a cross-sectional view taken along a direction perpendicular to the optical waveguide direction of the semiconductor laser device 150 according to the sixth embodiment, i.e., line B-B' in Fig. 25. Fig. 28 is a schematic view of the semiconductor laser device 150 according to the sixth embodiment.

[0064] <Element structure of semiconductor laser device according to sixth embodiment> A semiconductor laser device 150 according to the sixth embodiment includes a semiconductor substrate 1, a first semiconductor layer 2, a diffraction grating layer 8 formed inside the first semiconductor layer 2, an active layer 3 that emits laser light, a second semiconductor layer 4, a striped groove region 20a formed on the surface side of the second semiconductor layer 4 along the optical waveguide direction and consisting of a plurality of striped grooves 20 extending in a direction perpendicular to the optical waveguide direction, a surface electrode 10 formed on the surface of the second semiconductor layer 4 including the striped groove region 20a, and a back electrode 11 formed on the back side of the semiconductor substrate 1.

[0065] As shown in the cross-sectional view of Fig. 27, current blocking layers 6 are formed on both side surfaces of the mesa structure 15 including the active layer 3. Furthermore, as shown in the schematic view of Fig. 28, metal wiring 35 is provided on the surface electrode 10 including the stripe-shaped groove region 20a.

[0066] <Features of the semiconductor laser device according to the sixth embodiment> The semiconductor laser device 130 according to the fourth embodiment is characterized in that the diffraction grating layer 5 is formed inside the second semiconductor layer 4, whereas the semiconductor laser device 150 according to the sixth embodiment is characterized in that the diffraction grating layer 8 is formed inside the first semiconductor layer 2.

[0067] Furthermore, the semiconductor laser device 150 according to the sixth embodiment is arranged such that, at the location where the diffraction grating layer 8 faces the stripe groove region 20a, the bottom surface of each stripe groove 20 faces the upper surface of the diffraction grating 8a.

[0068] The semiconductor laser device 150 according to the sixth embodiment not only achieves the improved single mode characteristics obtained in the semiconductor laser device 130 according to the fourth embodiment, but also suppresses the optical axis misalignment that is pulled in the direction of the diffraction grating due to the refractive index difference, thereby achieving the effect of obtaining a high-quality beam shape.

[0069] <Method of Manufacturing Semiconductor Laser Device According to Sixth Embodiment> The following describes characteristic manufacturing steps in the method for manufacturing the semiconductor laser device 150 according to the sixth embodiment. Figures 29 to 31 are overviews showing the manufacturing method for the semiconductor laser device 150 according to the sixth embodiment.

[0070] First, a first semiconductor layer 2, an active layer 3, a second semiconductor layer 4, and a diffraction grating layer 8 inside the first semiconductor layer 2 are formed on a semiconductor substrate 1. Fig. 29 is a schematic view after the layers have been formed.

[0071] The diffraction grating layer 8 is formed by RIE using methane, hydrogen, chlorine, silicon tetrachloride, boron trichloride, hydrogen iodide, etc. The diffraction grating layer 8 may also be formed by selective wet etching using an acid or alkaline solution.

[0072] An insulating film is formed on the surface of the second semiconductor layer 4 by a CVD method or the like, and a plurality of periodic stripe-shaped openings are formed in this insulating film. Using this insulating film as a mask, a plurality of periodic stripe-shaped grooves 20 are formed on the surface side of the second semiconductor layer 4 by dry etching such as an RIE method. Figure 30 is a schematic view after the stripe-shaped grooves 20 have been formed.

[0073] A front surface electrode 10 is formed on the surface of the second semiconductor layer 4 in a portion including the plurality of stripe-shaped grooves 20. Fig. 31 is a schematic view of the front surface electrode 10 after it has been formed. The front surface electrode 10 is formed by a method such as sputtering, vapor deposition, or plating.

[0074] <Advantages of Sixth Embodiment> As described above, according to the semiconductor laser device of the sixth embodiment, a diffraction grating layer is formed inside the first semiconductor layer, and therefore, in addition to the effect of the fourth embodiment, an effect is achieved in that a semiconductor laser device capable of obtaining a higher quality beam shape is obtained.

[0075] Embodiment 7 Fig. 32 is a top view of a semiconductor laser device 160 according to the seventh embodiment. Fig. 33 is a cross-sectional view taken along the optical waveguide direction of the semiconductor laser device 160 according to the seventh embodiment, i.e., line A-A' in Fig. 32. Fig. 34 is a cross-sectional view taken along the direction perpendicular to the optical waveguide direction of the semiconductor laser device 160 according to the seventh embodiment, i.e., line B-B' in Fig. 32.

[0076] <Element structure of semiconductor laser device according to seventh embodiment> A semiconductor laser device 160 according to the seventh embodiment includes a semiconductor substrate 1, a first semiconductor layer 2, an active layer 3 that emits laser light, a second semiconductor layer 4, a diffraction grating layer 5 formed inside the second semiconductor layer 4, an etching stop layer 16, a third semiconductor layer 9, a striped groove region 20a formed on the front surface side of the third semiconductor layer 9 along the optical waveguide direction, with the etching stop layer 16 exposed at the bottom surface, and consisting of a plurality of striped grooves 20 extending in a direction perpendicular to the optical waveguide direction, a front surface electrode 10 formed on the front surface of the third semiconductor layer 9 including the striped groove region 20a, and a back surface electrode 11 formed on the back surface side of the semiconductor substrate 1.

[0077] As shown in the cross-sectional view of FIG. 34, current blocking layers 6 are formed on both side surfaces of a mesa structure 15 including an active layer 3.

[0078] <Features of the semiconductor laser device according to the seventh embodiment> In the semiconductor laser device 160 according to the seventh embodiment, an etching stop layer 16 is provided between the second semiconductor layer 4 and the third semiconductor layer 9. When forming the stripe-shaped grooves 20, selective wet etching is performed such that the third semiconductor layer 9 is etched but the etching stop layer 16 is not etched. In other words, the etching stop layer 16 is exposed at the bottom of the stripe-shaped grooves 20. As a result, the controllability of the depth of the stripe-shaped grooves 20 is significantly improved, because the depth of the stripe-shaped grooves 20 is equal to the thickness of the third semiconductor layer 9.

[0079] <Effects of the Seventh Embodiment> As described above, according to the semiconductor laser device of the seventh embodiment, an etching stop layer is provided between the second semiconductor layer and the third semiconductor layer, which significantly improves the controllability of the depth of the stripe-shaped groove, thereby achieving the effect of stably obtaining a semiconductor laser device in which the adhesion of the metal wiring to the surface electrode is improved.

[0080] Variation of embodiment 7. Fig. 35 is a top view of a semiconductor laser device 165 according to a modification of the seventh embodiment. Fig. 36 is a cross-sectional view taken along the optical waveguide direction of the semiconductor laser device 165 according to a modification of the seventh embodiment, i.e., line A-A' in Fig. 35. Fig. 37 is a cross-sectional view taken along the direction perpendicular to the optical waveguide direction of the semiconductor laser device 165 according to the modification of the seventh embodiment, i.e., line B-B' in Fig. 35.

[0081] <Features of the Semiconductor Laser Device According to the Modification of the Seventh Embodiment> In the semiconductor laser device 160 according to the seventh embodiment, the etching stop layer 16 is exposed at the bottom of the stripe-shaped groove 20, whereas in the semiconductor laser device 165 according to the modified example of the seventh embodiment, the etching stop layer 16 exposed at the bottom of the stripe-shaped groove 20 is further removed, and as a result, the second semiconductor layer 4 is exposed at the bottom of the stripe-shaped groove 20. As a result, an effect is achieved in that the influence of the change in refractive index caused by the etching stop layer 16 is eliminated in the stripe-shaped groove 20.

[0082] <Effects of the Seventh Embodiment> As described above, according to the semiconductor laser device of the modified example of the seventh embodiment, since an etching stop layer is provided between the second semiconductor layer and the third semiconductor layer, the controllability of the depth of the stripe-shaped groove is significantly improved, and since the etching stop layer on the bottom surface of the stripe-shaped groove is removed, it is possible to obtain an advantageous effect that a semiconductor laser device having improved adhesion of the metal wiring to the surface electrode can be obtained more stably.

[0083] Embodiment 8 Fig. 38 is a top view of a semiconductor laser device 170 according to embodiment 8. Fig. 39 is a cross-sectional view taken along a direction perpendicular to the optical waveguide direction of semiconductor laser device 170 according to embodiment 8, that is, along line BB' in Fig. 38.

[0084] <Element structure of semiconductor laser device according to embodiment 8> The semiconductor laser devices according to the first to seventh embodiments have a back surface electrode 11 provided on the back surface side of the semiconductor substrate 1. On the other hand, the semiconductor laser device 170 according to the eighth embodiment employs an element structure in which, instead of providing a back surface electrode 11 on the back surface of the semiconductor substrate 1, a first surface electrode 10a is provided on the surface of the second semiconductor layer 4 and a second surface electrode 10b is provided on the exposed portion of the first semiconductor layer 2, as shown in FIG.

[0085] A plurality of stripe-shaped grooves 21 are also provided on the surface side of the first semiconductor layer 2 in the exposed portion thereof, and the plurality of stripe-shaped grooves 21 are covered with the second surface electrode 10b. This is to improve the adhesion between the second surface electrode 10b and the metal wiring 35. The plurality of stripe-shaped grooves 21 form stripe-shaped groove regions 21a. The second surface electrode 10b is also referred to as a surface electrode for the first semiconductor layer.

[0086] <Effects of the Eighth Embodiment> As described above, according to the semiconductor laser device of embodiment 8, a plurality of stripe-shaped grooves are provided in the exposed portion of the first semiconductor layer, and the plurality of stripe-shaped grooves are covered with the second surface electrode, thereby achieving the effect of obtaining a semiconductor laser device with improved adhesion between the second surface electrode and the metal wiring.

[0087] Embodiment 9 Fig. 40 is a top view of a semiconductor laser device 180 according to the ninth embodiment. Fig. 41 is a cross-sectional view taken along a direction perpendicular to the optical waveguide direction of the semiconductor laser device 180 according to the ninth embodiment, that is, along the line BB' in Fig. 40.

[0088] The semiconductor laser device 180 according to the ninth embodiment is characterized in that it has a protective insulating film 45 on part of the top surface and on both side surfaces. By forming the protective insulating film 45, the reliability of the semiconductor laser device is improved.

[0089] <Effects of the 9th embodiment> As described above, the semiconductor laser device according to the ninth embodiment has a protective insulating film on a part of the top surface and on both side surfaces, which provides an effect of providing a highly reliable semiconductor laser device.

[0090] Embodiment 10 Fig. 42 is a top view of a semiconductor laser device 190 according to embodiment 10. Fig. 43 is a cross-sectional view taken along a direction perpendicular to the optical waveguide direction of semiconductor laser device 190 according to embodiment 10, i.e., along line BB' in Fig. 42.

[0091] A semiconductor laser device 190 according to the tenth embodiment is characterized in that a plurality of stripe-shaped grooves 20 are provided in a region other than the semiconductor laser portion. A second surface electrode 10c is provided on a surface of the device other than the one directly above the recombination region.

[0092] <Advantages of the Tenth Embodiment> As described above, according to the semiconductor laser device of embodiment 10, a plurality of stripe-shaped grooves are provided in the region other than the semiconductor laser portion, and the plurality of stripe-shaped grooves are covered with the second surface electrode, thereby achieving the effect of obtaining a semiconductor laser device with improved adhesion between the second surface electrode and the metal wiring.

[0093] Embodiment 11 Fig. 44 is a top view of a modulator-equipped semiconductor laser device, which is an example of the semiconductor laser device 200 according to the 11th embodiment. Fig. 45 is a cross-sectional view of the modulator-equipped semiconductor laser device, which is an example of the semiconductor laser device 200 according to the 11th embodiment, taken in the optical waveguide direction, i.e., along the line A-A' in Fig. 44.

[0094] A modulator-equipped semiconductor laser device, which is an example of the semiconductor laser device 200 according to the eleventh embodiment, includes a DFB laser section 200a and a modulator section 200b. A plurality of stripe-shaped grooves 20 are provided in both the DFB laser section 200a and the modulator section 200b. As a result, there is an effect that the adhesion between the surface electrode 10 and the metal wiring (not shown) provided in each of the DFB laser section 200a and the modulator section 200b is strengthened.

[0095] <Effects of Eleventh Embodiment> As described above, according to the semiconductor laser device of embodiment 11, a plurality of stripe-shaped grooves are provided in each of the DFB laser section and modulator section of the modulator-equipped semiconductor laser device, which is an example of a semiconductor laser device, and the plurality of stripe-shaped grooves are each covered with a surface electrode, thereby achieving the effect of obtaining a modulator-equipped semiconductor laser device with improved adhesion between the surface electrode and the metal wiring.

[0096] Note that, with regard to the semiconductor laser devices according to the first to tenth embodiments, a DFB laser device has been described as an example. However, the element structure of the present disclosure can also be applied to devices other than DFB laser devices, such as a semiconductor laser device with MMI (Multi-Mode-Interferometer-LD) and a semiconductor laser device with Mach-Zehnder.

[0097] Although the present disclosure describes various exemplary embodiments and examples, the various features, aspects, and functions described in one or more embodiments are not limited to application to a particular embodiment, but may be applied to the embodiments alone or in various combinations.

[0098] Therefore, countless variations not illustrated are conceivable within the scope of the technology of the present disclosure, including, for example, cases where at least one component is modified, added, or omitted, and cases where at least one component is extracted and combined with a component of another embodiment. [Explanation of symbols]

[0099] REFERENCE SIGNS LIST 1 semiconductor substrate, 2 first semiconductor layer, 3 active layer, 4 second semiconductor layer, 5, 8 diffraction grating layer, 5a, 8a diffraction grating, 6 current blocking layer, 7 contact layer, 9 third semiconductor layer, 16 etching stop layer, 10 surface electrode, 10a first surface electrode, 10b, 10c second surface electrode, 11 back surface electrode, 15 mesa structure, 20, 21 stripe-shaped groove, 20a, 21a stripe-shaped groove region, 22 convex portion, 30a, 30b reflective film, 35 metal wiring, 40, 40a insulating film, 41 resist film, 45 protective insulating film, 100, 110, 120, 130, 135, 140, 150, 160, 165, 170, 180, 190, 200 semiconductor laser device, 200a DFB laser section, 200b modulator section

Claims

1. a semiconductor substrate; a first semiconductor layer formed on the semiconductor substrate; an active layer formed on the first semiconductor layer; a second semiconductor layer formed on the active layer; a stripe-shaped groove region formed periodically along an optical waveguide direction on a surface side of the second semiconductor layer and including a plurality of stripe-shaped grooves extending in a direction perpendicular to the optical waveguide direction; a diffraction grating layer provided inside the second semiconductor layer, the diffraction grating layer including a plurality of diffraction gratings periodically formed along the optical waveguide direction, at least a portion of which is positioned to face the plurality of stripe-shaped grooves; a surface electrode formed on a surface of the second semiconductor layer including the stripe-shaped groove region, a semiconductor laser device, characterized in that the period of the plurality of stripe-shaped grooves is set to be N times (1≦N≦6: N is a natural number) the period of the plurality of diffraction gratings;

2. 2. The semiconductor laser device according to claim 1, wherein a contact layer is provided between the second semiconductor layer and the surface electrode.

3. 2. The semiconductor laser device according to claim 1, wherein the bottom surface of the stripe groove faces the upper surface of the diffraction grating at a position where the diffraction grating layer faces the stripe groove region.

4. 4. The semiconductor laser device according to claim 3, wherein the width of the bottom surface of the stripe-shaped groove in the optical waveguide direction is larger than the width of the diffraction grating in the optical waveguide direction.

5. 2. The semiconductor laser device according to claim 1, wherein, in a region where the diffraction grating layer faces the stripe-shaped groove region, a convex portion between each of the stripe-shaped grooves faces an upper surface of the plurality of diffraction gratings.

6. 6. The semiconductor laser device according to claim 1, wherein an insulating film is provided on a part of the surface of the second semiconductor layer.

7. 6. The semiconductor laser device according to claim 1, further comprising an insulating film provided between the second semiconductor layer and the surface electrode in at least a part of the region where the surface electrode is formed.

8. a semiconductor substrate; a first semiconductor layer formed on the semiconductor substrate; an active layer formed on the first semiconductor layer; a second semiconductor layer formed on the active layer; a stripe-shaped groove region formed periodically along an optical waveguide direction on a surface side of the second semiconductor layer and including a plurality of stripe-shaped grooves extending in a direction perpendicular to the optical waveguide direction; a diffraction grating layer provided inside the first semiconductor layer, the diffraction grating layer including a plurality of diffraction gratings periodically formed along the optical waveguide direction, at least a portion of which is positioned to face the plurality of stripe-shaped grooves; a surface electrode formed on a surface of the second semiconductor layer including the stripe-shaped groove region, a semiconductor laser device, characterized in that the period of the plurality of stripe-shaped grooves is set to be N times (1≦N≦6: N is a natural number) the period of the plurality of diffraction gratings;

9. 9. The semiconductor laser device according to claim 8, wherein in a portion where the diffraction grating layer and the stripe-shaped groove region face each other, the bottom surface of the stripe-shaped groove faces an upper surface of the diffraction grating.

10. 10. The semiconductor laser device according to claim 1, further comprising a first semiconductor layer surface electrode formed on the exposed portion of the first semiconductor layer.

11. 2. The semiconductor laser device according to claim 1, further comprising: a region including: the first semiconductor layer formed on the semiconductor substrate; the second semiconductor layer; a stripe-shaped groove region formed on a surface side of the second semiconductor layer and extending in a direction perpendicular to the optical waveguide direction, the stripe-shaped groove region comprising a plurality of stripe-shaped grooves; and a second surface electrode formed in a portion including the stripe-shaped groove region.

12. a semiconductor substrate; a first semiconductor layer formed on the semiconductor substrate; an active layer formed on the first semiconductor layer; a second semiconductor layer formed on the active layer; an etching stop layer formed on the second semiconductor layer; a third semiconductor layer formed on the etching stop layer; a stripe-shaped groove region including a plurality of stripe-shaped grooves periodically formed along an optical waveguide direction on a surface side of the third semiconductor layer, extending in a direction perpendicular to the optical waveguide direction, and having bottom surfaces formed in the etching stop layer or the second semiconductor layer; a diffraction grating layer provided inside the second semiconductor layer, the diffraction grating layer including a plurality of diffraction gratings periodically formed along the optical waveguide direction, at least a portion of which is positioned to face the plurality of stripe-shaped grooves; a surface electrode formed on a surface of the second semiconductor layer including the stripe-shaped groove region, a semiconductor laser device, characterized in that the period of the plurality of stripe-shaped grooves is set to be N times (1≦N≦6: N is a natural number) the period of the plurality of diffraction gratings;

13. 13. The semiconductor laser device according to claim 1, further comprising: a metal wiring connected to the surface electrode, the metal wiring having a contact portion with the surface electrode that includes at least a part of the stripe-shaped groove region.

14. 13. The semiconductor laser device according to claim 1, wherein the semiconductor laser device is any one of a DFB laser device, a semiconductor laser device with a modulator, a semiconductor laser device with an MMI, and a semiconductor laser device with a Mach-Zehnder.

15. 13. The semiconductor laser device according to claim 1, wherein both side surfaces are covered with a protective insulating film.

16. forming a first semiconductor layer, an active layer, a second semiconductor layer, and a diffraction grating layer inside the first semiconductor layer or the second semiconductor layer on a semiconductor substrate; forming an insulating film on a surface of the second semiconductor layer; periodically forming a plurality of stripe-shaped openings in the insulating film; forming a plurality of stripe-shaped grooves on the surface side of the second semiconductor layer by dry etching using the insulating film as a mask; forming a surface electrode on a surface of the second semiconductor layer in a stripe-shaped groove region consisting of the plurality of stripe-shaped grooves, a method for manufacturing a semiconductor laser device, wherein the diffraction grating layer comprises a plurality of diffraction gratings periodically formed along the optical waveguide direction, at least a portion of which is positioned opposite the plurality of stripe-shaped grooves, and the period of the plurality of stripe-shaped grooves is set to be N times (1≦N≦6: N is a natural number) the period of the plurality of diffraction gratings.

17. forming a first semiconductor layer, an active layer, a second semiconductor layer, and a diffraction grating layer inside the first semiconductor layer or the second semiconductor layer on a semiconductor substrate; forming an insulating film on a surface of the second semiconductor layer; periodically forming a plurality of stripe-shaped openings in the insulating film; forming a plurality of periodic stripe-shaped grooves in the second semiconductor layer by dry etching using the insulating film as a mask; coating a predetermined area with a resist film; etching and removing the insulating film with hydrofluoric acid using the resist film as a mask; forming a surface electrode on a surface of the second semiconductor layer in a stripe-shaped groove region consisting of the plurality of stripe-shaped grooves; and removing the resist film. a method for manufacturing a semiconductor laser device, wherein the diffraction grating layer comprises a plurality of diffraction gratings periodically formed along the optical waveguide direction, at least a portion of which is positioned opposite the plurality of stripe-shaped grooves, and the period of the plurality of stripe-shaped grooves is set to be N times (1≦N≦6: N is a natural number) the period of the plurality of diffraction gratings.

18. 18. The method for manufacturing a semiconductor laser device according to claim 16, wherein the dry etching is an RIE method using plasma containing iodine.

19. forming a metal wiring electrically connected to the surface electrode, the contact portion with the surface electrode including at least a part of the stripe-shaped groove region; The method for manufacturing a semiconductor laser device according to claim 16 or 17, further comprising:

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