A semiconductor device and a method of fabricating the same

Abstract

The application provides a semiconductor device and a manufacturing method thereof, and relates to the technical field of semiconductors. The semiconductor device comprises: a substrate; an epitaxial layer located on the front surface of the substrate, wherein the epitaxial layer comprises device regions and interval regions, the interval regions are located between two adjacent device regions, a groove is arranged between the device regions and the interval regions, and the bottom of the groove exposes the substrate; an APD unit located on the device regions; and an electrode located on the back surface of the substrate, wherein the electrode on the back surface of the substrate is provided with a light window corresponding to the position of the device regions. The semiconductor device and the manufacturing method thereof provided by the application have the advantages of being capable of improving optical and electrical crosstalk.

Description

Technical Field

[0001] This application relates to the field of semiconductor technology, and more specifically, to a semiconductor device and a method for manufacturing the same. Background Technology

[0002] Avalanche photodetectors have many advantages such as small size and high gain, and can be used in the detection of weak signals. In particular, the application of avalanche photodetector-based detection arrays in lidar, medical imaging and other scenarios has attracted widespread attention.

[0003] In practical applications, APD (avalanche photodiode) arrays often encounter problems such as optical crosstalk and electrical crosstalk. Optical crosstalk mainly involves avoiding crosstalk caused by obliquely incident light between adjacent pixels, and second-order photons emitted laterally to neighboring pixels also inevitably generate optical crosstalk. Electrical crosstalk is mainly caused by the lateral movement of photogenerated carriers. The occurrence of optical and electrical crosstalk seriously affects the performance of APD arrays.

[0004] In summary, existing APD arrays suffer from both optical and electrical crosstalk. Summary of the Invention

[0005] The purpose of this application is to provide a semiconductor device and its fabrication method to solve the problems of optical crosstalk and electrical crosstalk in the prior art of APD arrays.

[0006] To achieve the above objectives, the technical solutions adopted in the embodiments of this application are as follows:

[0007] On one hand, embodiments of this application provide a semiconductor device, the semiconductor device comprising:

[0008] Substrate;

[0009] An epitaxial layer located on the front side of the substrate, wherein the epitaxial layer includes a device region and a spacer region, the spacer region is located between two adjacent device regions, a trench is provided between the device region and the spacer region, and the bottom of the trench exposes the substrate;

[0010] The APD unit located on the device region; and,

[0011] An electrode located on the back side of the substrate, wherein an optical window is provided on the electrode on the back side of the substrate corresponding to the position of the device region.

[0012] Optionally, the semiconductor device further includes a pad layer located on the spacer region; wherein,

[0013] The surface of the pad layer is higher than the upper surface of the device region.

[0014] Optionally, the thickness of the spacer layer is 2-10 μm.

[0015] Optionally, the material of the spacer layer comprises one or a combination of polyimide, benzocyclobutene, silicon oxide, silicon nitride and metal.

[0016] Optionally, the semiconductor device further comprises a reflective film on the sidewall and bottom of the trench.

[0017] Optionally, the thickness of the reflective film is 100-1000 nm.

[0018] Optionally, the material of the reflective film comprises one or a combination of Al2O3, SiO2, SiN2, Ta2O5 and TiO2.

[0019] Optionally, the width of the spacer region is 1-1000 μm.

[0020] In another aspect, the embodiments of the present application further provide a semiconductor device manufacturing method, which comprises:

[0021] providing a substrate;

[0022] growing an epitaxial layer along the front surface of the substrate;

[0023] etching a trench along the epitaxial layer, and defining a device region and a spacer region by the trench; wherein the trench is located between adjacent device region and spacer region, and the bottom of the trench exposes the substrate;

[0024] manufacturing an APD unit along the surface of the device region;

[0025] manufacturing an electrode along the back surface of the substrate, and etching a light window at the position of the electrode relative to the device region.

[0026] Optionally, after the step of etching a trench along the epitaxial layer, and defining a device region and a spacer region by the trench, the method further comprises:

[0027] depositing a spacer layer along the spacer region;

[0028] evaporating a reflective film along the sidewall and bottom of the trench. Compared with the prior art, the present application has the following beneficial effects:

[0029] The application provides a semiconductor device and a manufacturing method thereof. The semiconductor device comprises a substrate, an epitaxial layer on the front surface of the substrate, wherein the epitaxial layer comprises device regions and interval regions, the interval regions are located between two adjacent device regions, a groove is arranged between the device regions and the interval regions, and the bottom of the groove exposes the substrate, an APD unit on the device region, and an electrode on the back surface of the substrate, wherein the electrode on the back surface of the substrate is provided with a light window corresponding to the position of the device region. In the application, the epitaxial layer is divided into regions, and the device regions and the interval regions are isolated, so that, on the one hand, photo-generated carriers cannot move laterally from the device regions to the interval regions, so that the photo-generated carriers of two adjacent APD units cannot move laterally, thereby effectively avoiding the electrical crosstalk. On the other hand, when secondary photons are emitted from one APD unit to an adjacent APD unit, the interval regions can play a certain isolation role, so that the problem of optical crosstalk can be effectively improved.

[0030] In order to make the above objectives, characteristics and advantages of the application more apparent, the following will describe a preferred embodiment in detail, and the accompanying drawings will be referred to, as follows. BRIEF DESCRIPTION OF DRAWINGS

[0031] In order to more clearly illustrate the technical solutions of the embodiments of the application, the following will briefly introduce the drawings needed to be used in the embodiments. It should be understood that the following drawings only show some of the embodiments of the application, and therefore should not be regarded as a limitation to the scope. For those skilled in the art, other related drawings can also be obtained without creative labor on the basis of these drawings.

[0032] Figure 1 A sectional view of the semiconductor device provided by the embodiment of the application.

[0033] Figure 2 A top view of the semiconductor device provided by the embodiment of the application.

[0034] Figure 3 Another sectional view of the semiconductor device provided by the embodiment of the application.

[0035] Figure 4 An arrangement schematic diagram of the light window provided by the embodiment of the application.

[0036] Figure 5 A first exemplary flowchart of the semiconductor device manufacturing method provided by the embodiment of the application.

[0037] Figure 6 A second exemplary flowchart of the semiconductor device manufacturing method provided by the embodiment of the application.

[0038] In the figure: 110 - substrate; 120 - epitaxial layer; 121 - device region; 122 - spacing region; 130 - APD unit; 140 - electrode; 150 - pad layer; 160 - reflective film. DETAILED DESCRIPTION

[0039] In order to make the objects, technical solutions, and advantages of the embodiments of the present application clearer, the following will be combined with the accompanying drawings for the embodiments of the present application to make a clear and complete description of the technical solutions in the embodiments of the present application. Obviously, the described embodiments are only some of the embodiments of the present application, rather than all the embodiments. The components of the embodiments of the present application described and shown in the accompanying drawings can be arranged and designed in various different configurations.

[0040] Therefore, the following detailed description of the embodiments of the present application provided in the accompanying drawings is not intended to limit the scope of the claimed present application, but only represents selected embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative work are within the scope of protection of the present application.

[0041] It should be noted that: similar reference numerals and letters represent similar items in the following drawings, therefore, once an item is defined in one drawing, it does not need to be further defined and explained in the subsequent drawings. Meanwhile, in the description of the present application, the terms "first", "second", and the like are only used to distinguish the description, and cannot be understood as indicating or implying relative importance.

[0042] It should be noted that: similar reference numerals and letters represent similar items in the following drawings, therefore, once an item is defined in one drawing, it does not need to be further defined and explained in the subsequent drawings. Meanwhile, in the description of the present application, the terms "first", "second", and the like are only used to distinguish the description, and cannot be understood as indicating or implying relative importance.

[0043] The following will be combined with the accompanying drawings to make a detailed description of some embodiments of the present application. The following embodiments and features in the embodiments can be combined with each other without conflict.

[0044] As described in the background, the current APD array has problems of optical crosstalk and electrical crosstalk in use, therefore, how to effectively suppress photoelectric crosstalk is a difficult problem to be solved in the design and manufacture of APD array.

[0045] Therefore, the present application provides a semiconductor device, which forms a device region and a spacing region on an epitaxial layer to effectively suppress photoelectric crosstalk.

[0046] The following will be combined with the accompanying drawings to make a detailed description of some embodiments of the present application. The following embodiments and features in the embodiments can be combined with each other without conflict.

[0047] As an optional implementation, please refer to Figure 1The semiconductor device comprises a substrate 110, an epitaxial layer 120, an APD unit 130 and an electrode 140, wherein the epitaxial layer 120 is located on the front surface of the substrate 110, and the epitaxial layer 120 comprises a device region 121 and a spacing region 122, the spacing region 122 is located between two adjacent device regions 121, and the device region 121 and the spacing region 122 are isolated, the spacing region 122 is used to prevent optical crosstalk and electrical crosstalk between the two adjacent device regions 121, the APD unit 130 is located on the device region 121, and the electrode 140 is located on the back surface of the substrate 110, and the electrode 140 on the back surface of the substrate 110 is provided with a light window corresponding to the position of the device region.

[0048] By dividing the epitaxial layer 120 into the device region 121 and the spacing region 122, the device region 121 and the spacing region 122 are isolated, thereby effectively improving the optical crosstalk and the electrical crosstalk. It should be noted that the isolation between the device region 121 and the spacing region 122 in the present application refers to that a groove is arranged between the device region 121 and the spacing region 122, and the bottom of the groove exposes the substrate, thereby realizing isolation through the groove.

[0049] Specifically, in combination with Figure 2 It can be known that, on the one hand, since a spacing region 122 is arranged in the middle of the two adjacent device regions 121, and the device region 121 and the spacing region 122 are isolated, the photo-generated carriers cannot move laterally from the device region 121 to the spacing region 122, so that the photo-generated carriers of the two adjacent APD units 130 cannot move laterally, thereby effectively avoiding the electrical crosstalk. On the other hand, when secondary photons are emitted from one APD unit 130 to the adjacent APD unit 130, since the spacing region 122 can play a certain isolation role, the problem of optical crosstalk can also be effectively improved.

[0050] As an optional implementation manner of the present application, the substrate 110 of the semiconductor device can be a highly doped InP substrate, and the epitaxial layer 120 is grown on the highly doped InP substrate. Compared with Si and GaAs materials, InP has high electro-optical conversion efficiency, high electron mobility, high working temperature, strong anti-radiation capability and good heat conduction. In addition, the InP substrate can be divided into an N-type substrate 110 and a P-type substrate 110. The N-type InP substrate can be doped with sulfur. Since sulfur has a significant impurity hardening effect in InP, dislocation-free single crystal growth can be realized. The P-type InP substrate can be doped with zinc. Zinc also has a strong impurity hardening effect, so that the dislocation is relatively low, and the device life is improved.

[0051] The epitaxial layer 120 is grown along the front surface of the substrate 110. In order to achieve different effects, the epitaxial layer 120 can be composed of multiple different layers, for example, the epitaxial layer 120 can include an absorption layer, a grading layer, a charge layer, a multiplication layer, and a contact layer. The contact layer is used to achieve ohmic contact with the APD unit 130. The multiplication layer is used to amplify the electrical signal. The charge layer is used to adjust the electric field distribution of each layer.

[0052] It can be understood that in the actual manufacturing process, the absorption layer, the grading layer, the charge layer, the multiplication layer, and the contact layer need to be grown layer by layer in sequence, which will not be described here.

[0053] After the epitaxial layer 120 is grown, the APD unit 130 needs to be manufactured on the device area of the epitaxial layer 120. After the APD unit 130 is manufactured, the APD unit 130 can be formed on the device area through processes such as doping, mesa etching, passivation, and gold-semi-contact, which will not be described here.

[0054] It should be noted that in an implementation, since the device structure requires the separation area 122 to be arranged separately from the device area 121, and different APD units 130 are arranged on the corresponding device area 121, when the APD unit 130 is manufactured, various etching means can be used to etch the trench between the APD unit 130 and the separation area 122. For example, photoresist can be coated as a mask, then patterned using photoresist, and finally etching is performed.

[0055] As an implementation, the width of the separation area is 1-1000 μm.

[0056] It should be further noted that in order to ensure that the epitaxial layer 120 is etched completely during etching, the etching needs to be stopped when the highly doped substrate 110 is exposed, that is, the etching stopping condition is that the substrate 110 is exposed. On this basis, when the etching is stopped, the epitaxial layer 120 can be etched completely or the substrate 110 can be etched partially, which will not be limited here.

[0057] It can be understood that in order to etch the separation area 122, a part of the epitaxial layer 120 needs to be reserved between the two adjacent APD units 130 during etching of the epitaxial layer 120. On this basis, when the epitaxial layer 120 is etched, two trenches are actually etched between the two adjacent APD units 130, such as trenches A and B as shown in FIG. 2, and the trenches A and B are separated. After etching is completed, the epitaxial layer 120 between the trenches A and B can be used as the separation area 122, and the epitaxial layer 120 on both sides of the trenches A and B can be used as the device area 121. Figure 1 It can be understood that in the actual manufacturing process, the absorption layer, the grading layer, the charge layer, the multiplication layer, and the contact layer need to be grown layer by layer in sequence, which will not be described here.

[0058] Please continue to refer to Figure 1 , Figure 1 As shown in FIG. 1C, two APD units 130 are shown, and the spacing region 122 is formed by etching groove A and groove B, so that the spacing region 122 in the middle is isolated from the device region 121 on the left by groove A and from the device region 121 on the right by groove B. Therefore, the photo-generated carriers of the APD unit 130 on the left cannot move to the right across groove A and groove B, and of course, the photo-generated carriers of the APD unit 130 on the right cannot move to the left across groove B and groove A, effectively avoiding electrical crosstalk. At the same time, the spacing region 122 is provided, which can block some secondary photons, so that the problem of optical crosstalk can also be effectively improved.

[0059] In order to make the improvement of optical crosstalk more obvious, please refer to Figure 3 In an implementation manner, the semiconductor device further includes a raised layer 150 on the spacing region 122, and a surface of the raised layer 150 is higher than an upper surface of the APD unit 130.

[0060] Since the APD unit 130 can actually be used as a point light source, in order to prevent the secondary photons from being emitted laterally to the adjacent APD unit 130, it is necessary to ensure that the secondary photons are blocked in the horizontal direction. At the same time, it is also necessary to prevent the crosstalk caused by the incident light between the APD units 130. Therefore, when the raised layer 150 is provided, the height of the raised layer 150 can be higher than the height of the APD unit 130, thereby achieving complete isolation between the two adjacent APD units 130, completely blocking the lateral secondary photons, and the effect of suppressing optical crosstalk is better.

[0061] In the present application, the material of the raised layer 150 is not limited, for example, the material of the raised layer 150 can include one or a combination of polyimide (PI), benzocyclobutene (BCB), silicon oxide, silicon nitride, and metal. Preferably, the material of the raised layer 150 can be selected as a non-transparent material, which is not limited here. For example, the raised layer 150 is made of polyimide, the thickness of the polyimide layer is controlled by spin coating, and after spin coating is completed, the polyimide layer on the spacing region 122 is reserved through a photoetching process, and the remaining polyimide layer is removed, and then the raised layer 150 is prepared through hard baking and curing.

[0062] Of course, the thickness of the polyimide layer is not limited in the present application, for example, the thickness of the raised layer 150 can be 2-10 μm.

[0063] In addition, although the interval region 122 can play a certain role in blocking the secondary photons, due to the light-transmitting property of the epitaxial layer 120 itself, the interval region 122 also has a certain light-transmitting property, so the interval region 122 has an effective blocking property for the secondary photons.

[0064] Therefore, in order to improve the blocking effect of the secondary photons and further suppress the optical crosstalk between adjacent APD units 130, as an implementation manner, the semiconductor device further comprises a reflective film 160 located at the groove side wall and the bottom wall; wherein the reflective film 160 is used to prevent the optical crosstalk between the two adjacent device regions 121.

[0065] For example, in the actual manufacturing process, the reflective film 160 can be made by evaporation process, and then the reflective film 160 in the remaining area is removed, and the reflective film 160 in the groove between the interval region 122 and the device region 121 is retained.

[0066] The reflective film 160 can reflect light, so when the secondary photons are emitted laterally, the secondary photons will not be emitted into the adjacent APD unit 130 due to the reflection of the reflective film 160, thereby effectively suppressing the optical crosstalk. At the same time, through the reflection of the reflective film 160, the escape of the secondary photons is also not easy, so that the display effect of the APD unit 130 is better.

[0067] It should be noted that the material of the reflective film 160 is not limited in the present application, for example, the material of the reflective film 160 can be one or a combination of Al2O3, SiO2, SiN2, Ta2O5 and TiO2. In addition, the thickness of the reflective film 160, the refractive index of the material and the wavelength of the light can be selected according to the actual situation to achieve the best light reflection effect. Generally, the thickness of the reflective film 160 ranges from 100 to 1000 nm.

[0068] As an implementation manner, please refer to Figure 4 The arrangement mode of the light window arranged on the electrode 140 on the back of the substrate 110 is the same as the arrangement mode of the APD unit 130, which is array arrangement. In addition, each light window is located at the corresponding position of the device region, that is, each light window is arranged at the orthographic projection position of the APD unit 130. In an implementation manner, in order to avoid the crosstalk caused by the oblique incident light between adjacent pixels as much as possible, the size of the light window is basically the same as the size of the APD unit 130, that is, the diameter of the light window is equal to or slightly larger than the diameter of the APD unit 130.

[0069] In addition, the size of the APD unit 130 is set to be substantially the same as the size of the light window, so that the front contact electrode 140 in the APD unit 130 can serve as a soldering point for subsequent packaging soldering, and meanwhile, the electrode 140 on the back of the substrate 110 adopts a coplanar electrode 140, which collectively provides conditions for flip-chip soldering of the APD unit 130.

[0070] In the process of making the light window, a window corresponding to the APD unit 130 can be made on the back of the substrate 110 and coated with a film, which can be an anti-reflection film, to increase the amount of light entering the light window. Then, the remaining area on the back of the substrate 110 is subjected to metal evaporation to serve as a coplanar back electrode 140.

[0071] Therefore, in the semiconductor device provided by the present application, the light and electrical crosstalk is suppressed by the structures such as the spacing area 122, the raised layer 150, and the reflective film 160, and the performance of the semiconductor device is effectively improved. Moreover, the semiconductor device structure is also easy to be packaged by flip-chip soldering.

[0072] Based on the above implementation manners, please refer to Figure 5 The present application also provides a semiconductor device manufacturing method, which comprises the following steps:

[0073] S102, providing a substrate.

[0074] S104, growing an epitaxial layer on the front of the substrate.

[0075] S106, etching a groove along the epitaxial layer, and defining a device area and a spacing area through the groove; wherein the groove is located between adjacent device areas and spacing areas, and the bottom of the groove exposes the substrate.

[0076] S108, manufacturing an APD unit along the surface of the device area.

[0077] S110, manufacturing an electrode on the back of the substrate, and etching a light window at the position of the electrode relative to the device area.

[0078] In the present application, the substrate can be a highly doped InP substrate. The epitaxial layer generally comprises multiple layers, which are an absorption layer, a gradual change layer, a charge layer, a multiplication layer, and a contact layer. In an implementation manner, when the epitaxial layer needs to be etched, a photoresist can be coated, and a corresponding groove can be etched according to the photoresist, so as to define the device area and the mounting area on the epitaxial layer. Then, the APD unit is continuously manufactured on the device area. It should be noted that, in order to isolate the device area and the spacing area by using the groove, the groove needs to be etched to expose the substrate when etching the groove.

[0079] And, when the electrode is made on the back of the substrate, a window can be etched on the area of the back of the substrate corresponding to the APD unit, plated as a light source incident light window, and then the remaining area of the back of the substrate is evaporated as a coplanar back electrode.

[0080] And, in order to make the effect of improving optical crosstalk more obvious, as one implementation, after S106, please refer to Figure 6 The method further comprises:

[0081] S1071, depositing a raised layer along the spacing area;

[0082] S1072, evaporating a reflective film along the sidewall and bottom of the groove.

[0083] The raised layer can effectively block the lateral emission of secondary photons, and at the same time, the raised layer can also avoid the crosstalk caused by oblique incident light between adjacent APD units, thereby improving the problem of optical crosstalk.

[0084] The material of the raised layer is not limited, for example, the material of the raised layer includes one or a combination of polyimide, benzocyclobutene, silicon oxide, silicon nitride and metal, and the height of the raised layer is also not limited, for example, it can be 2-10 μm, and in actual production, the material and thickness can be selected according to actual needs. For example, the thickness of the polyimide layer is controlled by spin coating, and after spin coating, the polyimide on the spacing layer is reserved through photolithography process, and the remaining polyimide is removed, and the preparation of the raised layer is completed through hard baking and curing.

[0085] In addition, the reflective film can prevent optical crosstalk between adjacent APD units in the device area and the spacing area.

[0086] The material of the reflective film includes one or a combination of Al2O3, SiO2, SiN2, Ta2O5 and TiO2, and the thickness of the reflective film can be 100-1000 nm. Of course, the thickness of the reflective film, the refractive index of the material and the wavelength of the light need to be calculated and selected according to the actual situation, and here is not limited.

[0087] It should be noted that S1071 and S1072 have no sequence, that is, the raised layer can be made first, and then the reflective film is evaporated; or the reflective film is evaporated first, and then the raised layer is made, which is not limited here.

[0088] In summary, the application provides a semiconductor device and a manufacturing method thereof. The semiconductor device comprises: a substrate; an epitaxial layer on the front side of the substrate, wherein the epitaxial layer comprises device regions and interval regions, the interval regions are located between two adjacent device regions, a groove is arranged between the device regions and the interval regions, and the bottom of the groove exposes the substrate; an APD unit on the device region; and an electrode on the back side of the substrate, wherein the electrode on the back side of the substrate is provided with a light window corresponding to the position of the device region. In the application, the epitaxial layer is divided into regions, and the device regions and the interval regions are isolated, so that, on the one hand, photo-generated carriers cannot move laterally from the device regions to the interval regions, so that the photo-generated carriers of two adjacent APD units cannot move laterally, thereby effectively avoiding electrical crosstalk. On the other hand, when secondary photons are emitted from one APD unit to an adjacent APD unit, the interval regions can play a certain isolation role, thereby effectively improving the problem of optical crosstalk.

[0089] The above only describes preferred embodiments of the application and is not intended to limit the application. The application can have various modifications and changes for those skilled in the art. Any modification, equivalent replacement, improvement, etc. within the spirit and principles of the application shall be included in the protection scope of the application.

[0090] It is obvious for those skilled in the art that the application is not limited to the details of the above exemplary embodiments, and the application can be implemented in other specific forms without departing from the spirit or essential characteristics of the application. Therefore, the embodiments should be regarded as exemplary and non-limiting, and the scope of the application is defined by the appended claims rather than the above description, and all changes falling within the meaning and scope of the equivalent elements of the claims are intended to be included in the application. Any reference signs in the claims should not be regarded as limiting the claims.

Claims

1. A semiconductor device, characterized by, The semiconductor device comprises: a substrate; an epitaxial layer on the front side of the substrate, wherein the epitaxial layer comprises device regions and spacer regions, the spacer regions being located between two adjacent device regions, and a trench being provided between the device regions and the spacer regions, the bottom of the trench exposing the substrate; an APD unit on the device regions; and an electrode on the back side of the substrate, wherein the electrode on the back side of the substrate is provided with a light window corresponding to the position of the device regions; The semiconductor device further comprises a raised layer on the spacer regions; wherein the surface of the raised layer is higher than the upper surface of the APD unit.

2. The semiconductor device of claim 1, wherein, The thickness of the raised layer is 2-10 μm.

3. The semiconductor device of claim 1, wherein, The material of the raised layer comprises one or a combination of polyimide, benzocyclobutene, silicon oxide, silicon nitride and metal.

4. The semiconductor device of claim 1, wherein, The semiconductor device further comprises a reflective film on the sidewall and the bottom of the trench.

5. The semiconductor device of claim 4, wherein, The thickness of the reflective film is 100-1000 nm.

6. The semiconductor device of claim 4, wherein, The material of the reflective film comprises one or a combination of Al2O3, SiO2, SiN2, Ta2O5 and TiO2.

7. The semiconductor device of claim 1, wherein, The width of the spacer region is 1-1000 μm.

8. A method of fabricating a semiconductor device, characterized by, A method for manufacturing the semiconductor device as claimed in any one of claims 1-7, the method comprising: providing a substrate; growing an epitaxial layer on the front side of the substrate; etching a trench along the epitaxial layer, and defining device regions and spacer regions by the trench; wherein the trench is located between two adjacent device regions and spacer regions, and the bottom of the trench exposes the substrate; manufacturing an APD unit on the surface of the device regions; manufacturing an electrode on the back side of the substrate, and etching a light window at the position of the electrode corresponding to the device regions.

9. The method of fabricating a semiconductor device of claim 8, wherein, After the step of etching a trench along the epitaxial layer, and defining device regions and spacer regions by the trench, the method further comprises: depositing a raised layer on the spacer regions; evaporating a reflective film on the sidewall and the bottom of the trench.

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