JP2003086899A - Semiconductor laser element and its manufacturing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a semiconductor laser element which can be manufactured by a simple process and obtains high stability, and its manufacturing method. SOLUTION: A P-type InP layer 21, an N-tape InP current block layer 23 and a P-type GaInAsP light waveguide layer 22 having a refractive index higher than that of the current block layer 23 are so formed that the transverse direction of a stripe part turns to InP/GaInAsP/InP. As a result, light confinement in the transverse direction can be achieved by using the difference of the refractive index between the light waveguide layer 22 and the current block layer 23 which are formed above an AlGaInAs/AlGaInAs active layer 14. It becomes unnecessary to expose a growth layer containing Al to the air, so that a laser forming process in surface treatment, regrowth, etc., can be made comparatively easy.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an embedded semiconductor laser device which can be easily manufactured and has high stability, and a manufacturing method thereof.

[0002]

2. Description of the Related Art FIG. 5 is a cross-sectional view of a conventional buried type semiconductor laser device on the emitting side. In FIG. 5, the semiconductor laser device 100 is formed on the n-type InP substrate 111 in order.
n-type InP buffer layer 112, n-type AlGaInAs-
SCH (separated light confinement) layer 113, AlGaInAs
/ AlGaInAs active layer 114, AlGaInAs-
SCH layer 117, p-type AlInAs electron barrier layer 118,
p-type InP clad layer 124 and contact layer 125
Are laminated to form a laminated structure.

Particularly, in this semiconductor laser device 100,
Part of the n-type AlGaInAs-SCH layer 113 and Al
GaInAs / AlGaInAs active layer 114 and Al
The GaInAs-SCH layer 117, the p-type AlInAs electron barrier layer 118, and a part of the p-type InP clad layer 124 are etched so as to be narrower than the width of other layers such as the n-type InP buffer layer 112. Thus, a so-called stripe is formed.

On the other hand, a p-type InP current blocking layer 119 and an n-type InP current blocking layer 120 are buried by regrowth in the portion removed by etching.
In particular, the p-type InP current blocking layer 119 includes the surface of the n-type AlGaInAs-SCH layer 113 and the AlGaInAs / AlGaInAs active layer 11 as illustrated.
4, AlGaInAs-SCH layer 117 and p-type Al
The n-type InP current blocking layer 120 is deposited so as to cover each side surface of the InAs electron barrier layer 118, and the p-type I
Deposited on the nP current blocking layer 119.

Here, the p-type InP current blocking layer 119 is formed.
InP used to form the n-type InP current blocking layer 120 has a lower refractive index than the layers forming the stripe. Therefore, the n-type InP current blocking layer 120, the p-type InP current blocking layer 119, the stripe portion, the p-type InP current blocking layer 119, and the n-type InP.
In the lateral direction of the drawing, which is arranged in the order of the current blocking layer 120, highly efficient light confinement is realized by the stripe portion located in the central portion thereof.

Further, in the stacking direction located on both sides of the stripe portion, the p-type InP current block layers 119, n are formed.
Since the p-type InP current blocking layer 120 and the p-type InP clad layer 124 are sequentially arranged, p-type semiconductor
An np structure is formed, which reduces current leakage. That is, by applying a voltage between the p-side electrode 126 formed on the front surface of the contact layer 125 and the n-side electrode 127 formed on the back surface of the n-type InP substrate 111,
A current is injected into the stripe portion. At this time, due to the existence of the p-n-p structure described above, the current is injected through the p-type InP current block layer 119 and the n-type InP current block layer 120 which are areas other than the stripe portion. It is possible to prevent unnecessary current from flowing.

FIG. 6 is a cross-sectional view of a conventional ridge type semiconductor laser device on the emitting side. In FIG. 6, the semiconductor laser device 200 comprises an n-type InP substrate 211, an n-type InP buffer layer 212, and an n-type AlGaInAs-SC.
H layer 213, AlGaInAs / AlGaInAs active layer 214, p-type AlInAs electron barrier layer 215, p-type G
aInAsP etching stop layer 216, p-type InP
The clad layer 224 and the contact layer 225 are formed to have a laminated structure. Further, the p-side electrode 226 is formed on the surface of the contact layer 225, and n-type InP is formed.
An n-side electrode 227 is formed on the back surface of the substrate 211.

Particularly, in this semiconductor laser device 200,
The p-type InP clad layer 224 and the contact layer 225 are etched so as to have a width narrower than that of other layers such as the p-type AlInAs electron barrier layer 215, so that a so-called stripe is formed. However, unlike the above-mentioned buried type semiconductor laser device, this stripe portion is not regrown on the portion removed by etching, and its side surface is only covered with the SiN film 217. That is, the ridge-type semiconductor laser device 20
0, current confinement is realized by this stripe portion, and air and semiconductor (p-type In
The confinement of light is realized by utilizing the difference in refractive index from the P clad layer 224).

The embedded semiconductor laser device 1 described above.
No. 00 and the ridge type semiconductor laser device 200, for example, in “Semiconductor laser and manufacturing method thereof” disclosed in Japanese Patent Laid-Open No. 9-36479, a semiconductor having a so-called self-alignment structure (SAS) structure is used. Laser devices have been proposed.

FIG. 7 is a cross-sectional view of the emission side of the semiconductor laser device disclosed in Japanese Patent Laid-Open No. 9-36479. Figure 7
In the semiconductor laser device 300, the n-type AlGaInAs optical waveguide layer 3 is sequentially formed on the n-type InP substrate 311.
12, InGaAsP / AlGaInAs active layer 31
3, p-type AlGaInAs optical waveguide layer 314, p-type Al
InAs clad layer 315, p-type InGaAsP etching stop layer 316, n-type InP current blocking layer 31
7, a p-type AlInAs burying layer 318 and a contact layer 325 are laminated. Further, the p-side electrode 326 is formed on the surface of the contact layer 325.
Is formed on the back surface of the n-type InP substrate 311 and the n-side electrode 3 is formed.
27 is formed.

Particularly, in this semiconductor laser device 300,
A stripe-shaped opening is provided in the center of the n-type InP current blocking layer 317, and the upper p-type AlInAs layer is formed.
The buried layer 318 is an n-type InP current blocking layer 317.
Is deposited in the opening as well as above. This n-type I
The nP current blocking layer 317 reduces the reactive current that does not contribute to the light emission and that flows in areas other than the stripe-shaped portion where the n-type InP current blocking layer 317 is not provided. Furthermore, since InP has a lower refractive index than AlInAs, The light is confined in the striped area where is injected.

[0012]

However, the above-mentioned conventional AlGaInAs-based buried type semiconductor laser device has a problem that each layer containing Al is exposed to the atmosphere in the process of forming the stripe portion. It is generally known that the crystal surface containing Al is more likely to be oxidized than other surfaces, and that it is difficult to perform surface treatment and remove a thermal oxide film inside the crystal growth apparatus. Therefore, when the p-type InP current block layer 119 is regrown on the side surface of the stripe portion exposed to the atmosphere, the crystallinity of the regrowth interface and the regrowth layer is not excellent, which greatly affects the device characteristics. I will end up. Further, since the stripe portion is composed of many layers of different materials, it is necessary to accurately control the width, shape, and depth of the stripe when forming the stripe by etching, and it is necessary to perform a large number of working steps. There is also a problem.

Further, in the above-mentioned conventional ridge type semiconductor laser device, since the contact layer 225 is included as a layer constituting the narrow stripe portion, the p-side electrode 226 formed on the upper surface together with the contact layer 225. However, there is a problem that the area becomes smaller and the resistance is increased. Further, since light is confined by the semiconductor and air in the stripe portion, the difference in refractive index between the stripe portion and the outside becomes very large, and considering the coupling with the optical fiber, the width of the stripe portion (ridge width ) Needs to be narrowed, and there is a problem that device design becomes complicated including the problem of high resistance.

Further, in the above-described semiconductor laser device having the SAS structure, the p-type AlInAs buried layer 318 is used as the regrown layer, but it is necessary to grow at a high temperature in order to obtain a good crystal of the grown layer containing Al. Become. The growth at such a high temperature can be achieved by using the p-type dopant as InGaAsP / Al.
This causes diffusion in the vicinity of the GaInAs active layer 313 and the interface of the n-type InP current block layer 317, which affects device characteristics such as an increase in oscillation threshold.

The present invention has been made in view of the above, and an object thereof is to provide a semiconductor laser device which can be manufactured by a simple process and which realizes high stability, and a manufacturing method thereof.

[0016]

In order to achieve the above-mentioned object, a semiconductor laser device according to a first aspect of the present invention comprises an active layer containing an Al mixed crystal material in at least a part thereof as a light emitting region, and the active layer. And an optical waveguide layer formed of a material having an energy band gap corresponding to a wavelength shorter than the light emitted from the active layer, and an optical waveguide layer laminated so as to fill both sides of the optical waveguide layer. And a buried layer formed of a material having a refractive index lower than that of the wave layer.

A semiconductor laser device according to a second aspect is the semiconductor laser device according to the first aspect, wherein the optical waveguide layer is formed of GaInAsP, the active layer is formed of AlGaInAs as a barrier layer, and the active layer is formed of a well layer. A
formed using lGaInAs or GaInAs,
The buried layer is formed of InP.

A semiconductor laser device according to a third aspect is the semiconductor laser device according to the first or second aspect, wherein a clad layer laminated on the optical waveguide layer and the buried layer, and on the clad layer. And a contact layer laminated on the.

According to a fourth aspect of the present invention, in the semiconductor laser element according to the third aspect, both sides of a portion of the clad layer laminated on the optical waveguide layer are formed by the buried layer. It is characterized by being embedded.

A semiconductor laser device according to a fifth aspect is the semiconductor laser device according to any one of the first to fourth aspects, wherein the semiconductor laser device is laminated under the optical waveguide layer and on the active layer. It is characterized by having an electron blocking layer.

A semiconductor laser device according to a sixth aspect is the semiconductor laser device according to any one of the first to fifth aspects, wherein the semiconductor laser device is a layer below the optical waveguide layer and on the electron barrier layer. And an etching stop layer formed of a material that is not etched by the solution that etches the optical waveguide layer.

A semiconductor laser device according to a seventh aspect is the semiconductor laser device according to the sixth aspect, wherein the etching stop layer is formed of InP.

A semiconductor laser device according to an eighth aspect is the semiconductor laser device according to any one of the first to seventh aspects, further comprising a separation light confinement (SCH) layer located below the active layer. It is characterized by that.

A semiconductor laser device according to a ninth aspect is the semiconductor laser device according to the seventh aspect, wherein the buried layer is formed of an n-type conductivity type semiconductor, and the clad layer and the etching stop layer. Is formed of a p-type conductivity type semiconductor.

According to a tenth aspect of the present invention, there is provided a method of manufacturing a semiconductor laser device, wherein an active layer serving as a light emitting region, an electron barrier layer,
In a method of manufacturing a semiconductor laser device in which an etching stop layer, an optical waveguide layer, and a first clad layer are sequentially stacked,
Forming a stripe-shaped mask on the first cladding layer, etching the first cladding layer with an etching solution that does not etch the optical waveguide layer, and not etching the etching stop layer Etching the optical waveguide layer with an etching solution, forming buried layers on both sides of the etched first cladding layer and the optical waveguide layer, and removing the mask,
Forming a second cladding layer on the first cladding layer and the buried layer.

[0026]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of a semiconductor laser device and a method of manufacturing the same according to the present invention will be described below in detail with reference to the drawings. The present invention is not limited to this embodiment.

FIG. 1 is a cross-sectional view of a semiconductor laser device according to an embodiment on the emitting side. In FIG. 1, a semiconductor laser device 10 is formed on an n-type InP substrate 11 in order.
n-type InP buffer layer 12, n-type AlGaInAs-S
CH layer 13, AlGaInAs / AlGaInAs active layer 14, p-type AlInAs electron barrier layer 15, p-type InP
Etching stop layer 16, p-type GaInAsP optical waveguide layer 22, p-type InP layer 21, p-type InP clad layer 24
And the contact layer 25 are laminated. A p-side electrode 26 is formed on the surface of the contact layer 25, and an n-side electrode 27 is formed on the back surface of the n-type InP substrate 11.

Particularly, in this semiconductor laser device 10, p
The type GaInAsP optical waveguide layer 22 and the p-type InP layer 21 are etched so as to be narrower than the width of other layers such as the p-type AlInAs electron barrier layer 15 to form a so-called stripe. On the other hand, the n-type InP current block layer 23 is buried by regrowth in the portion removed by etching.

Here, the p-type GaInAsP optical waveguide layer 22 forming the stripe portion has a higher refractive index than InP used to form the n-type InP current blocking layer 23, and also has AlGaInAs / AlGaInAs.
GaIn, which is a material having an energy band gap corresponding to light having a shorter wavelength than the light emitted from the active layer 14.
It is made of AsP. As a result, the n-type InP current blocking layer 23, the p-type GaInAsP optical waveguide layer 22,
P-type GaInAsP located in the center in the lateral direction of the drawing in which the p-type InP current blocking layer 23 is arranged in this order.
The optical waveguide layer 22 realizes highly efficient light confinement.

In the stacking direction located on both sides of the stripe portion, the p-type InP etching stop layer 16,
By arranging the n-type InP current blocking layer 23 and the p-type InP clad layer 24 in this order, the semiconductor pn
A -p structure is formed, which reduces current leakage. That is, a current is injected into the stripe portion by the voltage applied between the p-side electrode 26 and the n-side electrode 27. At this time, due to the existence of the p-n-p structure described above, a portion other than the stripe portion is provided. It is possible to prevent unnecessary current from flowing through the n-type InP current blocking layer 23 which is the region.

Next, the semiconductor laser device 1 shown in FIG.
The manufacturing method of 0 will be described. 2 and 3 are views showing a manufacturing process of the semiconductor laser device according to the present embodiment. First, MOCVD is performed on the n-type InP substrate 11.
(Metal Organic Chemical Vapor Deposition) device, etc.
P buffer layer 12, n-type AlGaInAs-SCH layer 1
3, AlGaInAs / AlGaInAs active layer 14,
A p-type AlInAs electron barrier layer 15, a p-type InP etching stop layer 16, a p-type GaInAsP optical waveguide layer 17, and a p-type InP layer 18 are sequentially formed (FIG. 2A).

Subsequently, a stripe mask 31 is formed on the p-type InP layer 18 at a position where a stripe portion is to be formed by a photolithography process (FIG. 2B). Then, using the hydrochloric acid-based etching solution, the p-type InP layer 18 is formed.
In FIG. 2, the portion where the stripe mask 31 is not formed is etched to form the p-type InP layer 21 (FIG. 2).
(C)). Particularly, the hydrochloric acid-based etching solution used here is a p-type GaInA layer located under the p-type InP layer 18.
A type that does not affect the sP optical waveguide layer 17 is used. As a result, in the step of forming the p-type InP layer 21, it is not necessary to control the etching in the depth direction. In addition, since the shape of the stripe mask 31 is defined also in the width direction, it is not necessary to control for that purpose.

Subsequently, in the state shown in FIG. 2C, only the etching solution is changed to a sulfuric acid-based etching solution, and the p-type In is added to the p-type GaInAsP optical waveguide layer 17.
The portion other than directly under the P layer 21 is etched to form p-type GaI.
The nAsP optical waveguide layer 22 is formed (FIG. 2D). In particular, the sulfuric acid-based etching solution used here is p-type Ga.
A type that does not affect the p-type InP etching stop layer 16 located below the InAsP optical waveguide layer 17 is used. In other words, the p-type InP etching stop layer 16 is the underlying p-type AlInAs electron barrier layer 15.
Plays a role of preventing the etching by the sulfuric acid-based etching solution described above. Therefore, also in this case, it is not necessary to control etching in the depth direction and the width direction in the step of forming the p-type GaInAsP optical waveguide layer 22.

Subsequently, in the state shown in FIG. 2D, MOCVD is performed using the stripe mask 31 as a mask.
Using an apparatus or the like, the n-type InP current blocking layer 23 is regrown on the p-type InP etching stop layer 16 (FIG. 3E). Then, the stripe mask 31 is removed,
A p-type InP clad layer 24 and a contact layer 25 are sequentially stacked on the n-type InP current blocking layer 23 and the p-type InP layer 21 (FIG. 3 (f)). Finally, the p-side electrode 26 is formed on the upper surface of the contact layer 25, and the n-side electrode 27 is formed on the back surface of the n-type InP substrate 11 (FIG. 3G).

FIG. 4 is experimental data showing current-output power characteristics and current-resistance characteristics of the semiconductor laser device according to this embodiment. The present inventors have found from the experimental data shown in FIG. 4 that the semiconductor laser device according to the present embodiment oscillates at a high output in a single mode, similar to the conventional embedded semiconductor laser device. . In FIG. 4, the solid line 41 indicates the current-output power characteristic,
The dotted line 42 indicates the current-resistance characteristic. Further, in order to obtain the experimental data, a semiconductor laser device in which the wavelength of the oscillated laser light is 1.3 μm band, the cavity length is 300 μm, and the oscillation threshold is 12.3 mA is used.

As described above, in the semiconductor laser device according to the present embodiment, since each layer is grown so that the lateral direction of the stripe portion becomes InP / GaInAsP / InP, AlGaInAs / AlGaIn is formed.
Optical confinement in the lateral direction can be realized by utilizing the difference in refractive index between the p-type GaInAsP optical waveguide layer 22 and the n-type InP current blocking layer 23 formed on the As active layer 14. As a result, it is not necessary to expose the growth layer containing Al to the atmosphere, and the laser fabrication process in surface treatment, re-growth, etc. can be made relatively easy.

Further, in the semiconductor laser device according to this embodiment, since the width of the contact layer 25 is not limited to the width of the stripe portion, the problem of increasing the resistance in the conventional ridge type semiconductor laser device does not occur. Further, in the semiconductor laser device according to the present embodiment, since the n-type InP current block layer 23 serving as a buried layer is formed of InP, its growth can be performed at a normal temperature, and the conventional SAS structure is obtained. The problem of diffusion of p-type dopant in the semiconductor laser device can be avoided.

Further, according to the method of manufacturing the semiconductor laser device of the present embodiment, when the p-type InP layer 21 forming the stripe portion is etched, the underlying p-type GaInA layer is formed.
A p-type GaI forming a stripe portion is formed by using an etching solution capable of using the sP optical waveguide layer 22 as a stop layer.
At the time of etching the nAsP optical waveguide layer 22, p-type I of the lower layer
Since an etching solution capable of using the nP etching stop layer 16 as a stop layer is used, it is not necessary to control the etching depth direction in particular, and the semiconductor laser device can be manufactured more easily than before.

In the above description, AlGaI
The nAs / AlGaInAs active layer 14 is formed of AlGaIn.
The As / GaInAs active layer may be replaced with p-type AlI.
The nAs electron barrier layer 15 may be replaced with a p-type AlGaInAs layer.

[0040]

As described above, according to the semiconductor laser device of the present invention, an Al mixed crystal system active layer which becomes a light emitting region, and a layer which is stacked above the active layer and emits light in the active layer. Optical waveguide layer formed of a material having an energy bandgap corresponding to light having a wavelength shorter than that of the light, and a material having a lower refractive index than the optical waveguide layer stacked so as to fill both sides of the optical waveguide layer. Since it is configured by including the buried layer formed in 1., lateral light confinement can be realized. As a result, there is no need to expose the growth layer containing Al to the atmosphere, and the laser manufacturing process in surface treatment, re-growth, etc. can be made relatively easy.

Further, according to the semiconductor laser device of the present invention, since the width of the contact layer is not limited to the narrow optical waveguide layer, the problem of increasing the resistance in the conventional ridge type semiconductor laser device does not occur. Since the buried layer is made of InP, its growth can be performed at a normal temperature, and the problem of diffusion of the p-type dopant in the conventional semiconductor laser device having the SAS structure can be avoided.

According to the method of manufacturing a semiconductor laser device of the present invention, the stripe portion is formed by using an etching solution that does not etch the lower optical waveguide layer when the first cladding layer forming the stripe portion is etched. Since an etching solution that does not etch the lower etching stop layer is used during the etching of the optical waveguide layer, it is not necessary to control the depth direction of the etching, and the semiconductor laser device can be manufactured more easily than before. There is an effect that can be.

[Brief description of drawings]

FIG. 1 is an emission side sectional view of a semiconductor laser device according to an embodiment.

FIG. 2 is a diagram showing a manufacturing process of the semiconductor laser device according to the embodiment.

FIG. 3 is a diagram showing a manufacturing process of the semiconductor laser device according to the embodiment.

FIG. 4 is a current of the semiconductor laser device according to the embodiment-
It is the experimental data showing the output power characteristic and the current-resistance characteristic.

FIG. 5 is a cross-sectional view of an emission side of a conventional embedded semiconductor laser device.

FIG. 6 is a cross-sectional view of an emission side of a conventional ridge type semiconductor laser device.

FIG. 7 is a cross-sectional view of an emitting side of a conventional semiconductor laser device having a SAS structure.

[Explanation of symbols]

10, 100, 200, 300 Semiconductor laser device 11, 111, 211, 311 n-type InP substrate 12, 112, 212 n-type InP buffer layer 13, 113, 213 n-type AlGaInAs-SCH
Layers 14, 114, 214 AlGaInAs / AlGaI
nAs active layer 15, 118, 215 p-type AlInAs electron barrier layer 16 p-type InP etching stop layer 17, 22 p-type GaInAsP optical waveguide layer 18, 21 p-type InP layer 23 n-type InP current blocking layer 24, 124, 224 p Type InP clad layer 25, 125, 225, 325 contact layer 26, 126, 226, 326 p-side electrode 27, 127, 227, 327 n-side electrode 31 stripe mask 117 AlGaInAs-SCH layer 119 p-type InP current block layer 120, 317 n-type InP current blocking layer 216, 316 p-type InGaAsP etching stop layer 217 SiN film 312 n-type AlGaInAs optical waveguide layer 313 InGaAsP / AlGaInAs active layer 314 p-type AlGaInAs optical waveguide layer 315 p-type AlInAs Cladding layer 318 p-type AlInAs burying layer

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Mitsumasa Ito             2-6-1, Marunouchi, Chiyoda-ku, Tokyo             Kawa Electric Industry Co., Ltd. F term (reference) 5F043 AA15 AA16 BB08 BB10 FF10                 5F073 AA13 AA53 AA73 CA15 CB02                       DA22

Claims (10)

[Claims] 1. An active layer containing an Al mixed crystal material in at least a part of a light emitting region, and an energy band laminated above the active layer and having a wavelength shorter than light emitted from the active layer. An optical waveguide layer formed of a material having a gap, and an embedded layer formed of a material having a refractive index lower than that of the optical waveguide layer, the embedded layer being laminated so as to fill both sides of the optical waveguide layer. Characteristic semiconductor laser device. 2. The optical waveguide layer is formed of GaInAsP, the active layer uses AlGaInAs as a barrier layer, and AlGaInAs or GaInAs is used as a well layer.
The semiconductor laser device according to claim 1, wherein the buried layer is formed of InP. 3. The clad layer laminated on the optical waveguide layer and the buried layer, and the contact layer laminated on the clad layer, according to claim 1 or 2. Semiconductor laser device. 4. The semiconductor laser device according to claim 3, wherein both sides of a portion of the cladding layer stacked on the optical waveguide layer are filled with the filling layer. 5. The semiconductor laser device according to claim 1, further comprising an electron barrier layer which is a lower layer of the optical waveguide layer and which is laminated on the active layer. . 6. An etching stop layer formed below the optical waveguide layer and on the electron barrier layer, the etching stop layer being formed of a material that is not etched by a solution that etches the optical waveguide layer. Claims 1 to 1 characterized
5. The semiconductor laser device according to any one of 5. 7. The semiconductor laser device according to claim 6, wherein the etching stop layer is formed of InP. 8. A separated light confinement (SCH) layer located below the active layer.
7. The semiconductor laser device according to any one of 7. 9. The buried layer is formed of a semiconductor having an n-type conductivity, and the clad layer and the etching stop layer are formed of a semiconductor having a p-type conductivity. Item 7. The semiconductor laser device according to item 7. 10. An active layer serving as a light emitting region, an electron barrier layer,
In a method of manufacturing a semiconductor laser device in which an etching stop layer, an optical waveguide layer, and a first cladding layer are sequentially stacked, a step of forming a stripe-shaped mask on the first cladding layer, and etching the optical waveguide layer Etching the first cladding layer with a non-etching solution, etching the optical waveguide layer with an etching solution not etching the etching stop layer, and etching the first cladding layer. A buried layer on both sides of the layer and the optical waveguide layer, removing the mask, and forming a second cladding layer on the first cladding layer and the buried layer. A method of manufacturing a semiconductor laser device, which comprises: