Optical semiconductor device

Abstract

Optical semiconductor device (50), which has: - a first light transceiver (51) formed with a first semiconductor substrate (111), and - a second light transceiver (52) formed with a second semiconductor substrate (112), and which is arranged to establish communication by means of optical signals mutually between the first and second transceivers (51, 52), where: - the first light transceiver (51) comprises: - the first semiconductor substrate (111); - a light-receiving unit (103) for receiving an optical signal (13a, 13b) and a light-emitting unit (102) for emitting the optical signal (13a, 13b) formed on the first semiconductor substrate (111); - a first interlayer film (31) covering the first semiconductor substrate (111), the light-receiving unit (103) and the light-emitting unit (102); - Fresnel lenses (61a, 61b) through which the optical signals (13a, 13b) can pass, which are formed respectively for the light-receiving unit (103) and the light-emitting unit (102) and which are formed on a planarized surface of the first interlayer film (31) located on the side thereof facing away from the first semiconductor substrate (111); and - a first protective film (81) covering the Fresnel lenses (61a, 61b) and the first interlayer film (31), the refractive index of which is greater than that of the first interlayer film (31) and the surface of which is planarized on its side facing away from the first interlayer film (31); and - the second light transceiver (52) comprises: - the second semiconductor substrate (112); - a light-receiving unit (115) for receiving an optical signal (13a, 13b) and a light-emitting unit (114) for emitting the optical signal (13a, 13b) formed on the second semiconductor substrate (112); - a second interlayer film (31) covering the second semiconductor substrate (112), the light-receiving unit (115) and the light-emitting unit (114); - Fresnel lenses (61a, 61b) through which the optical signals (13a, 13b) can pass, which are formed respectively for the light-receiving unit (115) and the light-emitting unit (114) and which are formed on a planarized surface of the second interlayer film (31) located on the side thereof facing away from the second semiconductor substrate (112); and - a second protective film (81) covering the Fresnel lenses (61a, 61b) and the second interlayer film (31), the refractive index of which is greater than that of the second interlayer film (31) and the surface of which is planarized on its side facing away from the second interlayer film (31); - the light-receiving unit (103) in the first light transceiver (51) and the light-emitting unit (114) in the second light transceiver (52) are placed so as to face each other, and the light-emitting unit (102) in the first light transceiver (51) and the light-receiving unit (115) in the second light transceiver (52) are placed so as to face each other; - the first protective film (81) in the first light transceiver (51) and the second protective film (81) in the second light transceiver (52) are bonded to each other directly or via a third intermediate film (113), - the first light transceiver (51) comprises a first integrated circuit (104) formed on the first semiconductor substrate (111), - the second light transceiver (52) comprises a second integrated circuit (104) formed on the second semiconductor substrate (112); and - the first integrated circuit (104) and the second integrated circuit (104) are arranged, after converting the optical signal (13a, 13b) received by the corresponding light-receiving unit (103, 115) into an electrical signal, to each carry out signal processing and to generate an electrical signal which serves as a basis for the optical signal (13a, 13b) to be emitted by the corresponding light-emitting unit (102, 114).

Description

TECHNICAL FIELDThe present invention relates to an optical semiconductor device which is a semiconductor light-treating device such as: a planar semiconductor light-receiving device for receiving (accepting) light; a planar semiconductor light-emitting device for emitting (transmitting) light; or a semiconductor device including optical elements such as a planar semiconductor light-receiving element for receiving light and a planar semiconductor light-emitting element for emitting light.BACKGROUND ARTIn Patent Document 1, an optical distance sensor is disclosed in which a light emitting element, a light receiving element for position detection, and an integrated circuit for control processing are mounted on a lead frame, and a lens on the light emitting side and a lens on the light receiving side are paired and placed above the light emitting element and the light receiving element for position detection, respectively, which is configured as a hybrid integrated circuit (module). In Patent Document 2, there is disclosed a semiconductor optical element (semiconductor device) in which an optical element and an electrically functional element are formed in an epitaxial layer on a semiconductor substrate, cap substrate on which a microlens is formed is placed above the semiconductor substrate, and an inner region between the semiconductor substrate and the cap substrate is sealed by a sealing structure formed on the outer circumferential side thereof, which is configured as a hybrid integrated circuit (module). In Patent Document 3, a light receiving module is disclosed in which an integrated circuit component and a photoelectric conversion element are embedded in an organic film by heating and pressing, in which a wiring pattern is formed, and a convex lens is formed on a surface of the organic film placed above the photoelectric conversion element. Patent Document 4 discloses an infrared light receiving integrated circuit in which a lens is formed on the back surface of a silicon wafer having an infrared light receiving element mounted thereon.Citation ListPATENT DOCUMENTPatent Document 1: Japanese Patent Application JP 2009- 097 872 (FIG. 1 )Patent Document 2: Japanese Patent JP 49 84170 B2 (FIG. 1 )Patent Document 3: Japanese Patent No. JP 41 52684 B2 (FIG. 3 )Patent Document 4: Japanese Patent Application JP 2016-526 155 AUS 2006 / 0 280 504 A1 relates to an optoelectronic integrated circuit device which has a vertical arrangement of integrated circuit layers, an optical signal being coupled between a first integrated circuit layer and a second integrated circuit layer. The optical signal is projected through a super lens element disposed between the first and second integrated circuit layers.US 2007 / 0 278 604 A1 discloses a radiation-detecting optoelectronic component having a semiconductor chip which has one or more radiation-sensitive zones for detecting electromagnetic radiation. In this case, the focusing of the electromagnetic radiation into the radiation-sensitive zones is effected by a diffractive element which is preferably integrated into the semiconductor chip. The diffractive element can be, in particular, a zone plate.WO 1991 / 02 380 A1 discloses a three-dimensional binary optical microlens structure made in the radiation-receiving rear side of a substrate of a radiation-detecting array. The microlens has a structure that achieves concentration of optical radiation within a desired spot size in the plane of a detector, thus enabling detectors with reduced active area to be fabricated. The incident radiation may be planar or prefocused by external optics. The methods of the invention provide a binary microlens optical solution for a Fresnel lens that achieves the desired optical concentration. The method also provides at least one fabrication mask layer on the back side of the array and creates the microlens structure by selectively removing material from the back side of the array.SUMMARY OF THE INVENTIONPROBLEMS TO BE SOLVED BY THE INVENTIONHeretofore, in semiconductor integrated circuits, it is common that signal processing is associated with signal transmission between functional circuits using wiring made of aluminum or a similar metal. However, according to the semiconductor integrated circuits using electric signals through the metal wirings, as the volume of transmitted information is expanded and the communication speed is accelerated, their increased power consumption and signal processing speed approach the allowable limits. Consequently, it is strongly demanded to put into practical use, for example, an optical semiconductor device capable of establishing signal transmission between functional circuits using an optical signal. The conventional semiconductor optical devices disclosed in Patent Documents 1 to 3, each including a light emitting element or / and a light receiving element, are each configured as a hybrid integrated circuit, so that in order to converge an optical signal (optical signals) from the light emitting element or / and for the light receiving element, it is necessary to attach a separate lens, which is not a semiconductor device, to the semiconductor device after manufacturing thereof. Thus, according to the conventional optical semiconductor device, in association with an increased number of the components, the number of the manufacturing steps thereof increases. This also restricts downsizing of the optical semiconductor device.In order to solve the problems as described above, an object of this invention is to achieve a light-treating semiconductor optical device that can reduce the number of components and the number of manufacturing steps and can be reduced.MEANS FOR SOLVING THE PROBLEMSThe object on which the invention is based is achieved in an optical semiconductor device according to the invention with the features of claim 1 and alternatively in an optical semiconductor device according to the invention with the features of claim 6. Advantageous refinements are the subject matter of the respective dependent claims.A semiconductor optical device according to the present invention includes, among other things, a semiconductor substrate; an optical communication unit provided on the semiconductor substrate as a light receiving unit for receiving an optical signal or a light emitting unit for emitting an optical signal; an interlayer film covering the semiconductor substrate and the optical communication unit; a Fresnel lens through which the optical signal passes provided on a planarized surface of the interlayer film located on its side opposite to the semiconductor substrate; and a protective film covering the Fresnel lens and the interlayer film whose refractive index is larger than that of the interlayer film and whose surface located on its side opposite to the interlayer film is planarized.EFFECT OF THE INVENTIONAccording to the semiconductor optical device of the invention, since the Fresnel lens through which the optical signal passes is provided on the planarized surface of the interlayer film covering the optical communication unit for receiving or emitting the optical signal and the planarized protective film covering the Fresnel lens and the interlayer film, it is possible to reduce the number of components and the number of manufacturing steps and achieve downsizing.BRIEF DESCRIPTION OF THE DRAWINGSFIG. 1 is a schematic diagram showing a cross-sectional structure of an optical semiconductor device according to an embodiment 1 of the invention. FIG. 2 is a diagram illustrating a wafer manufacturing step for the optical semiconductor device of FIG. 1. FIG. 3 is a diagram illustrating a wafer manufacturing step for the optical semiconductor device of FIG. 1. FIG. 4 is a diagram illustrating a wafer manufacturing step for the optical semiconductor device of FIG. 1. FIG. 5 is a diagram illustrating a wafer manufacturing step for the optical semiconductor device of FIG. 1. FIG. 6 is a diagram illustrating a wafer manufacturing step for the optical semiconductor device of FIG. 1. FIG. 7 is a diagram illustrating a wafer manufacturing step for the optical semiconductor device of FIG. 1. FIG. 8 is a diagram illustrating a first example of the shape in plan view of a Fresnel lens in FIG. 1 shows. FIG. 9 is a diagram illustrating a second example of the shape in plan view of the Fresnel lens in FIG. 1 shows. FIG. 10 is a diagram illustrating a third example of the shape in plan view of the Fresnel lens in FIG. 1 shows. FIG. 11 is a schematic diagram showing a cross-sectional structure of an optical semiconductor device according to an embodiment 2 of the invention. FIG. 12 is a schematic diagram showing a cross-sectional structure of an optical semiconductor device according to an embodiment 3 of the invention. FIG. 13 is a schematic diagram showing a cross-sectional structure of an optical semiconductor device according to an embodiment 4 of the invention. FIG. 14 is a schematic diagram showing a cross-sectional structure of another optical semiconductor device according to Embodiment 4 of the invention. FIG. 15 is a schematic diagram showing a cross-sectional structure of an optical semiconductor device according to an embodiment 5 of the invention. FIG. 16 is a schematic diagram showing a cross-sectional structure of another optical semiconductor device according to Embodiment 5 of the invention. FIG. 17 is a schematic diagram showing a cross-sectional structure of an optical semiconductor device according to an embodiment 6 of the invention. FIG. 18 is a diagram showing a plan view shape of a one-sided Fresnel lens in FIG. 17. FIG. 19 is a schematic diagram showing a cross-sectional structure of another optical semiconductor device according to Embodiment 6 of the invention. FIG. 20 is a schematic diagram showing a cross-sectional structure of an optical semiconductor device according to an embodiment 7 of the invention. FIG. 21 is a diagram showing a wafer manufacturing step for the optical semiconductor device of FIG. 20. FIG. 22 is a diagram showing a wafer manufacturing step for the optical semiconductor device of FIG. 20. FIG. 23 is a diagram showing a plan view shape of a Fresnel lens in FIG. 20. FIG. 24 is a diagram showing a plan view shape of a Fresnel lens according to an embodiment 8 of the invention. FIG. 25 is a diagram showing a plan view shape of a lens array according to Embodiment 8 of the invention. FIG. 26 is a schematic diagram showing a plan view of an optical semiconductor device according to Embodiment 8 of the invention. FIG. 27 is a schematic diagram showing a cross-sectional structure of an optical semiconductor device of FIG. 26.MODES FOR CARRYING OUT THE INVENTIONHere, with respect to an optical signal that is a light signal, the phrase "accepts the optical signal" is expressed as "receives the optical signal", and the phrase "sends the optical signal" is expressed as "emits the optical signal".Embodiment 1Next, a semiconductor optical device for receiving light, which is an embodiment of the invention and is represented by an avalanche photodiode (APD) or the like, will be described. FIG. 1 is a schematic diagram showing a cross-sectional structure of an optical semiconductor device according to an embodiment 1 of the invention. FIGS. 2 to 7 are diagrams each illustrating a wafer manufacturing step for the optical semiconductor device of FIG. 1. FIGS. 8 to 10 are diagrams showing first to third examples of the shape in plan view of a Fresnel lens in FIG. 1. A semiconductor optical device 50 of Embodiment 1 includes: a semiconductor substrate 11; a light receiving unit 12 provided on the semiconductor substrate 11 for receiving an optical signal 8 a, 8 b; an interlayer film 31 as an SiO2-based film; a Fresnel lens 61 provided on a surface of the interlayer film 31; and a protection film 81 as an SiN film covering the Fresnel lens 61. The semiconductor substrate 11 is a semiconductor substrate made of a single element or a chemical compound. The light receiving unit is a receiver unit having a receiving function in an optical communication unit to establish communication by means of optical signals.Wafer manufacturing steps for the optical semiconductor device 50 of Embodiment 1 will be described. First, in the step of manufacturing a substrate before lens formation, as shown in FIG. 2, the light receiving unit 12 is formed on the semiconductor substrate 11. The semiconductor substrate 11 on which the light receiving unit 12 is formed is the substrate before lens formation. As shown in FIG. 3, on the semiconductor substrate 11 on which the light receiving unit 12 is formed, an interlayer film 21 which is an interlayer film as an SiO2-based film (silicon-based oxide film) having a film thickness of 1.0 to 5.0 μm is deposited by a CVD (Chemical Vapor Deposition) method or the like. Due to the thicknesses of the light receiving unit 12 and wired electrodes (not shown) formed on the semiconductor substrate 11 under the interlayer film 21, a waveform is present on the surface of the interlayer film 21. As shown in FIG. 4, the interlayer film 21 is planarized such that the surface thereof is polished by a CMP (chemical mechanical polishing) method until the film thickness reaches 0.5 to 3.0 μm. An interlayer film corresponding to the thus polished interlayer film 21 is indicated by numeral 31. Note that, in FIGS. 1 to 7, a case is shown in which the surface of the light receiving unit 12 and the surface of the semiconductor substrate 11 are coplanar; however, such a case may also occur in which the surface of the light receiving unit 12 is positioned higher (closer to the Fresnel lens 61) than the surface of the semiconductor substrate 11 or in which the surface of the light receiving unit 12 is positioned lower (closer to the back surface of the semiconductor substrate 11) than the surface of the semiconductor substrate 11.Then, in order to form the Fresnel lens 61 on the surface of the interlayer film 31, a resist pattern 41 for forming the Fresnel lens is developed by a multi-exposure photolithography technique using an electron beam (EB) method. The resist pattern 41 is formed to match the shapes of concave portions of the Fresnel lens 61; for example, it is formed to have stepped shapes in which the thickness corresponding to a deep portion in the concave portion is thin, whereas the thickness corresponding to a shallow portion in the concave portion is thick. As shown in FIG. 5, the concave portions of the Fresnel lens 61 are formed in the interlayer film 31 by a dry etching method, so that convex portions 62a, 62b, 62c and 62d are formed. FIG. 5 shows concave portions of the Fresnel lens 61 during etching, and shows a state in which the resist pattern 41 remains on the convex portions of the Fresnel lens 61 after resist portions for the respective deep portions in the concave portions gradually disappear with the progress of etching by etching ions 15 for the concave portions.After completion of the etching step of the interlayer film 31, the resist pattern 41 is removed so that the Fresnel lens 61 provided with the convex portions 62a, 62b, 62c and 62d as shown in FIG. 6 is formed on the surface of the interlayer film 31. Examples of the shape in plan view of the Fresnel lens 61 are illustrated in FIGS. 8 to 10. The first example shown in FIG. 8 is a concentric circular shape, the second example shown in FIG. 9 is a square shape provided with curvatures at four corners, and the third example shown in FIG. 10 is a rectangular shape provided with curvatures at four corners. The shapes in plan view from the first example to the third example are each provided as a concentric ring shape. Generally, the Fresnel lens 61 having a concentric circular shape is used; however, the shape of the second example, the shape of the third example, or a shape other than the shape in plan view of the Fresnel lens 61 may be selected according to the shape of the light receiving unit 12. The resist pattern 41 is formed to have fine widths of a residual resist corresponding to the shape in plan view of the Fresnel lens 61. The resist pattern 41 for forming each of the shapes in plan view of FIGS. 8 to 10 is formed such that a width of a residual resist for forming the central convex portion 62 ais wider than a width of a residual resist for forming each of the other convex portions 62 b, 62 c, and 62 d, and the width of the residual resist for forming each of the convex portions 62 b, 62 c, and 62 dis gradually narrowed in this order.After the Fresnel lens 61 is formed as shown in FIG. 6, in order to secure moisture resistance, as shown in FIG. 7, a protective film 71 comprising an SiN film (silicon nitride film) having a refractive index larger than that of the interlayer film 31 as an SiO2-based film and having a film thickness of 1.0 to 3.0 μm is deposited by a CVD method or the like to cover the interlayer film 31 on which the Fresnel lens 61 is formed. On the surface of the protective film 71, a wavy shape is exhibited due to the concavo-convex shape of the underlying Fresnel lens 61. Since the protective film 71 covers the SiO2-based film such as quartz glass, it can be referred to as a glass coating film. The protective film 71 having the corrugated shape is planarized such that the surface thereof is polished by a CMP method until the film thickness reaches 0.5 to 1.0 μm. The optical semiconductor device 50 after the protective film 71 has been planarized and the wafer manufacturing steps have been completed is shown in FIG. 1. A protective film corresponding to the thus planarized protective film 71 is indicated by reference numeral 81.Operations and effects according to the optical semiconductor device 50 of Embodiment 1 will be described. According to the semiconductor optical device for receiving light shown in FIG. 1, which is an avalanche photodiode (APD) or the like, the optical signal 8 aenters the planarized protection film 81 as a SiN film, so that the optical signal 8 bconvergeed by the Fresnel lens 61 formed on the interlayer film 31 as a SiO2-based film under the protection film 81 is received by the light receiving unit 12. The refractive index of the protective film 81 is 1.9, and the refractive index of the interlayer film 31 is 1.4, so that the semiconductor optical device 50 of Embodiment 1 can converge optical signals at angles larger than those according to a conventional APD using a single-layer SiO2 lens. Further, according to the semiconductor optical device 50 of Embodiment 1, the light receiving sensitivity of the light receiving unit 12 can be increased in such a manner that the focal length of the Fresnel lens 61 is adjusted according to the wavelength of the optical signal 8 a, 8 bon the basis of the film thickness of the interlayer film 31, the intervals between the concentric circles in the structure of the Fresnel lens 61, and the dry etching depth thereof. Further, in the optical semiconductor device 50 according to Embodiment 1, the protective film 81 is provided on the upper surface thereof, so that sufficient moisture resistance is secured.It is noted that the intervals between the concentric circles in the structure of the Fresnel lens 61 correspond to the widths of the convex portions 62 b, 62 c, and 62 d. Using the shape shown in FIG. 8 in plan view of the Fresnel lens 61, a description will be given. A circle at the central portion (first circle) is an outer peripheral circle of the convex portion 62 a(inner peripheral circle of the convex portion 62 b), a circle on the outer side thereof (second circle) is an outer peripheral circle of the convex portion 62 b(inner peripheral circle of the convex portion 62 c), a third circle on the outer side thereof (third circle) is an outer peripheral circle of the convex portion 62 c(inner peripheral circle of the convex portion 62 d), and a fourth circle (fourth circle) provided on the outermost periphery is an outer peripheral circle of the convex portion 62 d. The interval between the first circle and the second circle in the structure of the Fresnel lens 61 in FIG. 8 corresponds to the width of the convex portion 62 b. Similarly, in the structure of the Fresnel lens 61 in FIG. 8, the interval between the second circle and the third circle corresponds to the width of the convex portion 62 c, and the interval between the third circle and the fourth circle corresponds to the width of the convex portion 62 d.According to the semiconductor optical device 50 of Embodiment 1, unlike the conventional APD for which it is necessary to assemble a semiconductor optical device for receiving light and a self-contained lens having a self-contained package, the Fresnel lens 61 is formed in the wafer manufacturing steps for the semiconductor optical device for receiving light. Consequently, it is possible to make the number of components thereof smaller than that of the conventional apparatus and thus achieve downsizing. Further, according to the semiconductor optical device 50 of Embodiment 1, since the Fresnel lens 61 is formed in the wafer manufacturing steps for the semiconductor device for receiving light, it is possible to eliminate such a step of assembling a self-contained lens with a self-contained package and thus to reduce the number of manufacturing steps thereof. According to the optical semiconductor device 50 of Embodiment 1, since the number of components and the number of manufacturing steps are reduced, it becomes possible to achieve cost reduction. Moreover, according to the optical semiconductor device 50 of Embodiment 1, since the light receiving sensitivity is increased, it also becomes possible to achieve reduction in power consumption.As described above, the semiconductor optical device 50 of Embodiment 1 includes: the semiconductor substrate 11; an optical communication unit provided on the semiconductor substrate 11 as the light receiving unit 12 for receiving the optical signal 8 a, 8 b; the interlayer film 31 covering the semiconductor substrate 11 and the optical communication unit; the Fresnel lens 61 through which the optical signal 8 a, 8 bpasss provided on the planarized surface of the interlayer film 31 located on its side opposite to the semiconductor substrate 11; and the protective film 81 covering the Fresnel lens 61 and the interlayer film 31 whose refractive index is larger than that of the interlayer film 31 and whose surface located on its side opposite to the interlayer film 31 is planarized. According to the semiconductor optical device 50 of Embodiment 1, since the Fresnel lens 61 through which the optical signal 8 a, 8 bpasss is provided on the planarized surface of the interlayer film 31 covering the optical communication unit for receiving (or emitting) the optical signal 8 a, 8 band the planarized protective film 81 covering the Fresnel lens 61 and the interlayer film 31, it is possible to reduce the number of components and the number of manufacturing steps and achieve downsizing.Embodiment 2FIG. 11 is a schematic diagram showing a cross-sectional structure of an optical semiconductor device according to an embodiment 2 of the invention. A semiconductor optical device 50 of Embodiment 2 is an example of a semiconductor device for emitting light such as a laser diode, a light emitting diode, or the like. A semiconductor optical device 50 of Embodiment 2 includes: a semiconductor substrate 11; a light emitting unit 91 provided on the semiconductor substrate 11 to emit an optical signal 9 a, 9 b; an interlayer film 31 as an SiO2-based film; a Fresnel lens 61 provided on a surface of the interlayer film 31; and a protection film 81 as an SiN film covering the Fresnel lens 61. The light emitting unit is a transmitter unit having a transmission function in an optical communication unit to establish communication by means of optical signals. The optical semiconductor device 50 of Embodiment 2 is different from the optical semiconductor device 50 of Embodiment 1 in that the light emitting unit 91 is formed on the semiconductor substrate 11 in place of the light receiving unit 12. The wafer manufacturing steps for the semiconductor optical device 50 of Embodiment 2 are similar to those in Embodiment 1. The semiconductor substrate 11 on which the light emitting unit 91 is formed is the substrate before lens formation.Operations and effects according to the optical semiconductor device 50 of Embodiment 2 will be described. According to the semiconductor optical device for emitting light shown in FIG. 11, which is a laser diode, a light emitting diode or the like, the optical signal 9a emitted from the light emitting unit 91 is refracted by the Fresnel lens 61 formed on the interlayer film 31 as an SiO2-based film so as to pass through the protective film 81 formed on this lens as an SiN film to be radiated to the outside. The refractive index of the protective film 81 is 1.9, and thus the refractive index of the protective film 81 is larger than the refractive index of 1.4 of the interlayer film 31, so that at the boundary between the interlayer film 31 and the protective film 81, the optical signal is refracted further toward the central side. This prevents the optical signal 9a, 9b from being scattered and attenuated.According to the optical semiconductor device 50 of Embodiment 2, in contrast to the conventional optical semiconductor device for which it is necessary to assemble a semiconductor device for emitting light and a self-contained lens with a self-contained package, the Fresnel lens 61 is formed in the wafer manufacturing steps for the optical semiconductor device for emitting light. Thus, it is possible to make the number of components thereof smaller than that of the conventional apparatus and thus achieve downsizing. Further, according to the semiconductor optical device 50 of Embodiment 2, since the Fresnel lens 61 is formed in the wafer manufacturing steps for the semiconductor device for emitting light, it is possible to eliminate such a step of assembling a self-contained lens with a self-contained package and thus reduce the number of manufacturing steps thereof. According to the optical semiconductor device 50 of Embodiment 2, since the number of components and the number of manufacturing steps are reduced, it becomes possible to achieve cost reduction. Moreover, according to the optical semiconductor device 50 of Embodiment 2, since the optical signal 9 a, 9 bis prevented from being diffused and attenuated, it also becomes possible to achieve reduction in power consumption.As described above, the semiconductor optical device 50 of Embodiment 2 includes: the semiconductor substrate 11; a communication unit provided on the semiconductor substrate 11 as the light emitting unit 91 for emitting the optical signal 9 a, 9 b; the interlayer film 31 covering the semiconductor substrate 11 and the optical communication unit; the Fresnel lens 61 through which the optical signal 9 a, 9 bpasss provided on the planarized surface of the interlayer film 31 located on its side opposite to the semiconductor substrate 11; and the protective film 81 covering the Fresnel lens 61 and the interlayer film 31 whose refractive index is larger than that of the interlayer film 31 and whose surface located on its side opposite to the interlayer film 31 is planarized. According to the semiconductor optical device 50 of Embodiment 2, since the Fresnel lens 61 through which the optical signal 9 a, 9 bpasss is provided on the planarized surface of the interlayer film 31 covering the optical communication unit for emitting the optical signal 9 a, 9 band the planarized protective film 81 covering the Fresnel lens 61 and the interlayer film 31, it is possible to reduce the number of components and the number of manufacturing steps and achieve downsizing.Embodiment 3FIG. 12 is a schematic diagram showing a cross-sectional structure of an optical semiconductor device according to an embodiment 3 of the invention. A semiconductor optical device 50 of Embodiment 3 is an example of a high-function semiconductor optical device such as an optical sensor or the like that includes an integrated circuit, a light emitting unit, and a light receiving unit. The semiconductor optical device 50 of Embodiment 3 includes: a semiconductor substrate 101 on which an integrated circuit 104 such as a signal processing circuit or the like and an integrated circuit 105 such as a power circuit or the like are formed; a light emitting unit 102 provided (formed or mounted) on the semiconductor substrate 101 to emit an optical signal 9 a, 9 b; a light receiving unit 103 provided (formed or mounted) on the semiconductor substrate 101 to receive an optical signal 8 a, 8 b; an interlayer film 31 as an SiO2-based film; Fresnel lenses 61 a, 61 bprovided on a surface of the interlayer film 31; and a protective film 81 as an SiN film covering the Fresnel lenses 61 a, 61 b. The light emitting unit 102 is a planar light emitting structural unit such as a laser diode, a light emitting diode, or the like. The light receiving unit 103 is a planar light receiving structural unit such as an avalanche photodiode (APD) or the like. The Fresnel lens 61 ais a Fresnel lens for receiving light formed above the light receiving unit 103, namely, on the surface of the interlayer film 31 (the surface thereof on the side opposite to the side facing the semiconductor substrate 101). The Fresnel lens 61 bis a Fresnel lens for radiating light formed above the light emitting unit 102, namely, on the surface of the interlayer film 31 (the surface thereof on the side opposite to the side facing the semiconductor substrate 101). For the Fresnel lenses, numeral 61 is used in common, and numerals 61a, 61b are used when they are separately described. The integrated circuit 104 performs signal processing after converting the optical signal 8 a, 8 breceptored by the light receiving unit 103 into an electrical signal, and generates an electrical signal serving as a basis for the optical signal 9 a, 9 bto be emitted from the light emitting unit 102.The optical semiconductor device 50 of Embodiment 3 is different from the optical semiconductor device 50 of Embodiment 1 in that, in addition to the light receiving unit 103, the light emitting unit 102 and the integrated circuits 104, 105 are formed on the semiconductor substrate 101. In the wafer manufacturing steps for the optical semiconductor device 50 of Embodiment 3, the steps of forming the planarized interlayer film 31, the Fresnel lens 61 and the planarized protective film 81 are the same as those in Embodiment 1. In the substrate manufacturing step before lens formation, the integrated circuits 104, 105 are formed on the semiconductor substrate 101, and thereafter the light emitting unit 102 and the light receiving unit 103 are formed or mounted on the semiconductor substrate 101. The semiconductor substrate 101 on which the integrated circuits 104, 105 are formed and the light emitting unit 102 and the light receiving unit 103 are formed or mounted is the substrate before lens formation. In the case of mounting the light emitting unit 102 and the light receiving unit 103 on the semiconductor substrate 101, the planar light emitting structural unit and the planar light receiving structural unit each formed in a chip shape are mounted on the semiconductor substrate 101. Note that in FIG. 12, the integrated circuits 104, 105 are formed under the sheet plane, for example, so as to be indicated by frames in a dotted line.Operations and effects according to the optical semiconductor device 50 of Embodiment 3 will be described. The optical signal 9a emitted from the light emitting unit 102 shown in Fig. 12, which is a planar light emitting structural unit such as a laser diode, a light emitting diode or the like, is refracted by the Fresnel lens 61b formed on the interlayer film 31 as an SiO2-based film to pass through the protective film 81 formed on this lens as an SiN film to be radiated to the outside. The refractive index of the protective film 81 is 1.9, and thus the refractive index of the protective film 81 is larger than the refractive index of 1.4 of the interlayer film 31, so that at the boundary between the interlayer film 31 and the protective film 81, the optical signal is refracted further toward the central side. This prevents the optical signal 9a, 9b from being scattered and attenuated.The optical signal 9 bmitted from the light emitting unit 102 impinges on an object such as an obstacle, a door, or the like, and is then reflected therefrom. The optical signal thus reflected is incident on the semiconductor optical device 50 as the optical signal 8 a, and the optical signal 8 aappears into the planarized protection film 81 as a SiN film, so that the optical signal 8 bconvergeed by the Fresnel lens 61 aformed on the interlayer film 31 as a SiO2-based film under the protection film 81 is received by the light receiving unit 103 as a planar light receiving structural unit such as an avalanche photodiode (APD) or the like formed or mounted on the semiconductor substrate 101. The refractive index of the protective film 81 is 1.9, and the refractive index of the interlayer film 31 is 1.4, so that the semiconductor optical device 50 of Embodiment 3 can converge optical signals at angles larger than those according to a conventional APD using a single-layered SiO2 lens, thereby enhancing the light receiving sensitivity of the light receiving unit 103. Accordingly, even when the optical signal 8 a, 8 bis weak, the semiconductor optical device 50 of Embodiment 3 can detect this signal.The received optical signal 8 bis subjected to analog or digital signal processing by the integrated circuit 104 formed on the semiconductor substrate 101 such as a signal processing circuit or the like, so that the presence, the distance, and the position of the object are determined by calculation by the integrated circuit 104, and then information on the presence, the distance, and the position of the object is transmitted to another control system outside the semiconductor optical device 50. Meanwhile, according to the wavelength of the optical signal 8 a, 8 b, 9 a, 9 b, the focal lengths of the Fresnel lenses 61 a, 61 bare set on the basis of the film thickness of the interlayer film 31 as the SiO2-based film, the intervals between the concentric circles in the structure of each of the Fresnel lenses 61 a, 61 b, and the dry etching depth thereof. Further, in the optical semiconductor device 50 of Embodiment 3, the protective film 81 is provided on the upper surface thereof, so that sufficient moisture resistance is secured.According to the optical semiconductor device 50 of Embodiment 3, unlike the conventional optical semiconductor device that needs to have a module configuration in which a semiconductor device including a planar light emitting element and a planar light receiving element and a self-contained lens are assembled with a self-contained package, the light emitting unit 102 and the light receiving unit 103 are formed or mounted on the common semiconductor substrate 101 and further the integrated circuits 104, 105 are formed and the Fresnel lens 61 is formed in the wafer manufacturing steps for the optical semiconductor device. Thus, it is possible to make the number of components thereof smaller than that of the conventional apparatus and thus achieve downsizing. According to the semiconductor optical device 50 of Embodiment 3, since the Fresnel lens 61 is formed in the wafer manufacturing steps for the semiconductor optical device, it is possible to eliminate such a step of assembling a self-contained lens with a self-contained package and thus reduce the number of manufacturing steps thereof, thereby simplifying the manufacturing steps. According to the optical semiconductor device 50 of Embodiment 3, since the number of components and the number of manufacturing steps are reduced, it becomes possible to achieve cost reduction. The semiconductor optical device 50 of Embodiment 3 can detect this signal even when the optical signal 8 a, 8 bis weak, and the light receiving sensitivity of the light receiving unit 103 is enhanced. Thus, it becomes possible to achieve reduction in power consumption. With such a configuration of the semiconductor optical device 50 of Embodiment 3, manufacturing steps are simplified as compared with the conventional device, and it becomes possible to achieve downsizing and cost reduction, and moreover, since the optical signal 9 a, 9 bmitted from the light emitting unit 102 is prevented from being scattered and attenuated, it becomes possible to achieve a high-function semiconductor optical device such as an optical sensor or the like, which can achieve increase in sensitivity and reduction in power consumption.Embodiment 4FIG. 13 is a schematic diagram showing a cross-sectional structure of an optical semiconductor device according to an embodiment 4 of the invention. A semiconductor optical device 50 of Embodiment 4 is an example of a semiconductor optical device provided with two high-function semiconductor optical devices of Embodiment 3 each including the integrated circuits, the light emitting unit, and the light receiving unit, and wherein / mutual / transmission (communication) of optical signals is established between these devices using the respective light emitting units and the light receiving units. The semiconductor optical device 50 of Embodiment 4 is a semiconductor optical device including two light transceivers 51, 52, and in which the light transceivers 51, 52 are bonded to each other using an interlayer film 113 made of an organic or inorganic material. The light transceiver 51 includes: a semiconductor substrate 111 on which an integrated circuit 104 such as a signal processing circuit or the like and an integrated circuit 105 such as a power circuit or the like are formed; a light emitting unit 102 provided (formed or mounted) on the semiconductor substrate 111 to emit an optical signal 13 a; a light receiving unit 103 provided (formed or mounted) on the semiconductor substrate 111 to receive an optical signal 13 b; an interlayer film 31 as an SiO2-based film; Fresnel lenses 61 a, 61 bprovided on a surface of the interlayer film 31; and a protective film 81 as an SiN film covering the Fresnel lenses 61 a, 61 b. As in Embodiment 3, the light emitting unit 102 is a planar light emitting structural unit such as a laser diode, a light emitting diode, or the like. As in Embodiment 3, the light receiving unit 103 is a planar light receiving structural unit such as an avalanche photodiode (APD) or the like. The Fresnel lens 61 aof the light transceiver 51 is a Fresnel lens for receiving light formed in a remote region separated from the light receiving unit 103 in a direction perpendicular thereto, namely, on the surface of the interlayer film 31 (the surface thereof on the side opposite to the side facing the semiconductor substrate 111). The Fresnel lens 61 bof the light transceiver 51 is a Fresnel lens for radiating light formed in a remote region separated from the light emitting unit 102 in a direction perpendicular thereto, namely, on the surface of the interlayer film 31 (the surface thereof on the side opposite to the side facing the semiconductor substrate 111).The light transceiver 52 includes: a semiconductor substrate 112 on which an integrated circuit 104 such as a signal processing circuit or the like and an integrated circuit 105 such as a power circuit or the like are formed; a light emitting unit 114 provided (formed or mounted) on the semiconductor substrate 112 to emit the optical signal 13 b; a light receiving unit 115 provided (formed or mounted) on the semiconductor substrate 112 to receive the optical signal 13 a; an interlayer film 31 as an SiO2-based film; Fresnel lenses 61 a, 61 bprovided on a surface of the interlayer film 31; and a protective film 81 as an SiN film covering the Fresnel lenses 61 a, 61 b. As in Embodiment 3, the light emitting unit 114 is a planar light emitting structural unit such as a laser diode, a light emitting diode, or the like. As in Embodiment 3, the light receiving unit 115 is a planar light receiving structural unit such as an avalanche photodiode (APD) or the like. The light emitting unit 114 and the light receiving unit 115 of the light transceiver 52 are placed so as to face the light receiving unit 103 and the light emitting unit 102 of the light transceiver 51, respectively. The Fresnel lens 61 aof the light transceiver 52 is a Fresnel lens for receiving light formed in a remote region separated from the light receiving unit 115 in a direction perpendicular thereto, namely, on the surface of the interlayer film 31 (the surface thereof on the side opposite to the side facing the semiconductor substrate 112). The Fresnel lens 61 bof the light transceiver 52 is a Fresnel lens for radiating light formed in a remote region separated from the light emitting unit 114 in a direction perpendicular thereto, namely, on the surface of the interlayer film 31 (the surface thereof on the side opposite to the side facing the semiconductor substrate 112).In FIG. 13, an example of the semiconductor optical device 50 is shown, wherein two light transceivers 51, 52 are bonded to each other using the interlayer film 113 made of an organic or inorganic material. As shown in FIG. 14, since the surfaces of the respective light transceivers 51, 52 that are located farthest from the semiconductor substrates 111, 112 in directions perpendicular thereto are provided by the planarized protective films 81, it is permissible to directly bond the light transceiver 51 and the light transceiver 52 to each other by being firmly contacted using a van der Waals force. FIG. 14 is a schematic diagram showing a cross-sectional structure of another optical semiconductor device according to an embodiment 4 of the invention. The other semiconductor optical device 50 shown in FIG. 14 is different from the semiconductor optical device 50 shown in FIG. 13 in that the interlayer film 113 is not provided and the light transceiver 51 and the light transceiver 52 are directly bonded to each other by utilizing a van der Waals force in a firmly contacted state.Operations and effects according to the optical semiconductor device 50 of Embodiment 4 will be described. The optical signal 13a emitted from the light emitting unit 102 shown in Fig. 13, which is a planar light emitting structural unit such as a laser diode, a light emitting diode or the like, is refracted by the Fresnel lens 61b formed on the interlayer film 31 as an SiO2-based film so as to pass through the protective film 81 as an SiN film formed in a remote area in the running direction of this signal. The refractive index of the protective film 81 is 1.9, and thus the refractive index of the protective film 81 is larger than the refractive index of 1.4 of the interlayer film 31, so that at the boundary between the interlayer film 31 and the protective film 81, the optical signal is refracted further toward the central side. This prevents the optical signal 13 bfrom being scattered and attenuated.The optical signal 13 amitted from the light emitting unit 102 passes through the interlayer film 113 made of an organic or inorganic material, and is then received by the light receiving unit 115 as a planar light receiving structural unit such as an avalanche photodiode (APD) or the like formed or mounted on the semiconductor substrate 112 of the light transceiver 52. The optical signal 13 aindicated on the light transceiver 52 first enters the planarized protection film 81 as an SiN film and is then converged by the Fresnel lens 61 aformed on the interlayer film 31 as an SiO2-based film placed on the semiconductor substrate 112 side as viewed from the protection film 81, and is received by the light receiving unit 115. The refractive index of the protective film 81 is 1.9 and the refractive index of the interlayer film 31 is 1.4, so that the light receiving unit 115 of the light transceiver 52 can converge optical signals at angles larger than those according to a conventional APD using a single-layered SiO2 lens, thereby enhancing the light receiving sensitivity of the light receiving unit 115. Accordingly, even if the optical signal 13a is weak, the light receiving unit 115 of the light transceiver 52 can detect this signal.The optical signal 13 areceptored by the light receiving unit 115 of the light transceiver 52 is subjected to analog or digital signal processing by the integrated circuit 104 such as a signal processing circuit or the like formed on the semiconductor substrate 112, and the processed signal is transmitted as the optical signal 13 bfrom the light emitting unit 114. The optical signal 13 bmitted from the light emitting unit 114 of the light transceiver 52 passes through the Fresnel lens 61 bformed as an SiO2-based film on the interlayer film 31, the protective film 81 as an SiN film, and the interlayer film 113 made of an organic or inorganic material in a direction opposite to that of the optical signal 13 a, and is converged by the Fresnel lens 61 aformed as an SiN film on the protective film 81 and the interlayer film 31 as an SiO2-based film in the light transceiver 51 and then accepted by the light receiving unit 103.According to the semiconductor optical device 50 of Embodiment 4, since optical communication is established between two light transceivers 51, 52 via a shortest path, it is possible to reduce the output power of each of the optical signals 13 a, 13 bto a minimum. Meanwhile, in the semiconductor optical device 50 of Embodiment 4, according to the wavelengths of the optical signals 13 a, 13 band the path, the focal lengths of the Fresnel lenses 61 a, 61 bare respectively optimally set by adjusting the film thickness of the interlayer film 31 as the SiO2-based film, the intervals between the concentric circles in the structure of each of the Fresnel lenses 61 a, 61 b, and / or the dry etching depth thereof. Further, in the optical semiconductor device 50 of Embodiment 4, the respective protective films 81 are provided in respective remote regions apart from the semiconductor substrates 111, 112 of the light transceivers 51, 52 in directions perpendicular thereto, namely, on the surfaces of the respective interlayer films 31 (their surfaces on the sides opposite to the sides facing the semiconductor substrates 111, 112), so that sufficient moisture resistance is ensured.As described above, in semiconductor integrated circuits, it is common that signal processing is associated with signal transmission between functional circuits using wiring made of aluminum or a similar metal. Even in the case of a conventional optical semiconductor device as a light-treating semiconductor device, communication between the conventional optical semiconductor device in which a semiconductor integrated circuit is formed and another semiconductor device, which may be an optical semiconductor device, based on an electric signal is also established using the metal wiring. According to the electrical signal-based communication using the metal wiring, there is a problem of heat generation and a limited communication speed. Thus, for the semiconductor optical device that performs communication using an optical signal, it is necessary to reduce heat generation and increase the communication speed. When optical communication is to be established between the semiconductor optical devices, such a problem occurs that the number of components increases due to an optical fiber, an optical fiber, and the like, and therefore the planar area increases.In contrast, according to the optical semiconductor device 50 of Embodiment 4, since two semiconductor devices, for example, the light transceivers 51, 52 are bonded to each other and optical signals are used for mutual communication thereof, it becomes possible to reduce the number of components and significantly reduce the area. In the light transceivers 51, 52, the respective Fresnel lenses 61 a, 61 bhave been formed by a wafer manufacturing process (in the wafer manufacturing steps) on a different side corresponding to each of the light emitting units 102, 114 for transmitting the optical signals and the light receiving units 103, 115 for accepting the optical signals, respectively, and which is away from each of the semiconductor substrates 111, 112 in a direction perpendicular thereto. This makes it possible to achieve downsizing, reduction in power consumption, and cost reduction for each of the light transceivers 51, 52 as semiconductor optical devices. Moreover, for the optical semiconductor device 50 of Embodiment 4 in which two semiconductor devices, for example, the light transceivers 51, 52, are bonded to each other, this also enables downsizing, reduction in power consumption, and cost reduction to be achieved.According to the semiconductor optical device 50 of Embodiment 4, since it is provided with the light transceivers 51, 52 for establishing their mutual optical communication, and the light emitting unit 114 and the light receiving unit 115 of the light transceiver 52 are placed facing the light receiving unit 103 and the light emitting unit 102 of the light transceiver 51, respectively, it is possible to reduce heat generation and increase communication speed as compared with the conventional device. Further, according to the semiconductor optical device 50 of Embodiment 4, since each of the light transceivers 51, 52 includes the light emitting unit, the light receiving unit, and the Fresnel lenses integrally formed in the wafer manufacturing steps, it is possible to reduce the number of components and the number of manufacturing steps of each of the light transceivers 51, 52, thereby achieving downsizing and cost reduction of each of the light transceivers 51, 52 and further achieving downsizing and cost reduction of the device as a whole.Embodiment 5FIG. 15 is a schematic diagram showing a cross-sectional structure of an optical semiconductor device according to an embodiment 5 of the invention. A semiconductor optical device 50 of Embodiment 5 is an example of a semiconductor optical device provided with two high-function semiconductor optical devices each including integrated circuits, a light emitting unit, and a light receiving unit, and wherein / or mutual / transmission / reception (communication) of optical signals is configured between these devices using the respective light emitting units and the respective light receiving units. The semiconductor optical device 50 of Embodiment 5 is a semiconductor optical device provided with: a light transceiver 51 including, in addition to the integrated circuits, the light emitting unit, and the light receiving unit, an electrical connection configuration for establishing electrical connection with an external system and an optical communication configuration (an external system-related optical communication unit) for establishing optical communication with an external system; and a light transceiver 52 including, in addition to the integrated circuits, the light emitting unit, and the light receiving unit, an electrical connection configuration directed to the light transceiver 51; and wherein the light transceivers 51, 52 are bonded to each other using an interlayer film 113 made of an organic or inorganic material.The light transceiver 51 includes: a semiconductor substrate 121 on which an integrated circuit 104 such as a signal processing circuit or the like and an integrated circuit 105 such as a power circuit or the like are formed; a light emitting unit 102 provided (formed or mounted) on the semiconductor substrate 121 to emit an optical signal 13 a; a light receiving unit 103 provided (formed or mounted) on the semiconductor substrate 121 to receive an optical signal 13 b; another light emitting unit 122 provided (formed or mounted) on the semiconductor substrate 121 to transmit (emit) an optical signal 13 cfrom the light transceiver 51 to an external system; another light receiving unit 123 provided (formed or mounted) on the semiconductor substrate 121 to accept (receive) an optical signal 13d transmitted (emitted) from an external system to the light transceiver 51; an electrode unit 106 to make electrical connection with the light transceiver 52 facing the light transceiver 51; an electrode unit 107 to make electrical connection with an external system; an interlayer film 31 as an SiO2-based film; respective Fresnel lenses 61a, 61b provided on a surface of the interlayer film 31; and a protective film 81 as an SiN film covering the Fresnel lenses 61a, 61b. As in Embodiment 3, the light emitting units 102, 122 are each a planar light emitting structural unit such as a laser diode, a light emitting diode, or the like. As in Embodiment 3, the light receiving units 103, 123 are each a planar light receiving structural unit such as an avalanche photodiode (APD) or the like. The two Fresnel lenses 61a of the light transceiver 51 are Fresnel lenses for receiving light formed in remote regions separated from the light receiving units 103, 123 in directions perpendicular thereto, namely, on the surface of the interlayer film 31 (the surface thereof on the side opposite to the side facing the semiconductor substrate 121). The two Fresnel lenses 61b of the light transceiver 51 are Fresnel lenses for radiating light formed in remote regions separated from the light emitting units 102, 122 in directions perpendicular thereto, namely, on the surface of the interlayer film 31 (the surface thereof on the side opposite to the side facing the semiconductor substrate 121). The light emitting unit 122 is a transmitting unit having a transmitting function in an external system-related optical communication unit for establishing communication by optical signals with an external system. The light receiving unit 123 is a receiver unit having a receiving function in the external system-related optical communication unit for establishing communication by means of optical signals with an external system. The light emitting unit for establishing communication with an external system may be referred to as an external system-related light emitting unit, and the light receiving unit for establishing communication with an external system may be referred to as an external system-related light receiving unit.The electrode unit 106 includes: a wired electrode 116 disposed on the semiconductor substrate 121; a wired electrode 117 disposed on the front surface side of the interlayer film 31; a connection metal 118 connecting the wired electrode 116 to the wired electrode 117; and a bump electrode 124 disposed to be connected to the wired electrode 117 and exposed from the protection film 81. The electrode unit 107 has a structure similar to that of the electrode unit 106, and includes: a wired electrode 116 disposed on the semiconductor substrate 121; a wired electrode 117 disposed on the front surface side of the interlayer film 31; a connection metal 118 connecting the wired electrode 116 to the wired electrode 117; and a bump electrode 125 disposed to be connected to the wired electrode 117 and exposed from the protection film 81. The electrode unit 106 is connected to an electrode unit 108 of the light transceiver 52, and is an electrode unit used for power supply to the light transceiver 52 and signal processing without reference to optical communication with the light transceiver 52. The electrode unit 107 is an electrode unit used for power supply between an external system and the light transceiver 51 and signal processing. Note that, although an electrode unit used for power supply and an electrode unit used for signal processing are separate electrode units, in FIG. 15, an electrode unit 106 and an electrode unit 107 are respectively illustrated as the electrode units.The light transceiver 52 includes: a semiconductor substrate 126 on which an integrated circuit 104 such as a signal processing circuit or the like is formed; a light emitting unit 114 provided (formed or mounted) on the semiconductor substrate 126 to emit the optical signal 13 b; a light receiving unit 115 provided (formed or mounted) on the semiconductor substrate 126 to receive the optical signal 13 a; an electrode unit 108 to make electrical connection with the light transceiver 51 facing the light transceiver 52; an interlayer film 31 as a SiO2-based film; Fresnel lenses 61 a, 61 bprovided on a surface of the interlayer film 31; and a protective film 81 as a SiN film covering the Fresnel lenses 61 a, 61 b. As in Embodiment 3, the light emitting unit 114 is a planar light emitting structural unit such as a laser diode, a light emitting diode, or the like. As in Embodiment 3, the light receiving unit 115 is a planar light receiving structural unit such as an avalanche photodiode (APD) or the like. The light emitting unit 114 and the light receiving unit 115 of the light transceiver 52 are placed to face the light receiving unit 103 and the light emitting unit 102 of the light transceiver 51, respectively. The Fresnel lens 61 aof the light transceiver 52 is a Fresnel lens for receiving light formed in a remote region separated from the light receiving unit 115 in a direction perpendicular thereto, namely, on the surface of the interlayer film 31 (the surface thereof on the side opposite to the side facing the semiconductor substrate 126). The Fresnel lens 61 bof the light transceiver 52 is a Fresnel lens for radiating light formed in a remote region separated from the light emitting unit 114 in a direction perpendicular thereto, namely, on the surface of the interlayer film 31 (the surface thereof on the side opposite to the side facing the semiconductor substrate 126).The electrode unit 108 includes: a wired electrode 128 disposed on the semiconductor substrate 126; a wired electrode 129 disposed on the front surface side of the interlayer film 31; a connection metal 130 connecting the wired electrode 128 to the wired electrode 129; and a bump electrode 127 disposed to be connected to the wired electrode 129 and exposed from the protection film 81. The electrode unit 108 is connected to the electrode unit 106 of the light transceiver 51, and is an electrode unit used for power supply from the light transceiver 51 and used for signal processing without reference to optical communication with the light transceiver 51. Note that although an electrode unit used for power supply and an electrode unit used for signal processing are separate electrode units, in FIG. 15, an electrode unit 108 is shown as the electrode units.In FIG. 15, an example of the semiconductor optical device 50 is shown, wherein two light transceivers 51, 52 are bonded to each other using the interlayer film 113 made of an organic or inorganic material. As shown in FIG. 16, since the surfaces of the respective light transceivers 51, 52 located farthest from the semiconductor substrates 121, 126 in directions perpendicular thereto are provided by the planarized protective films 81, it is permissible to directly bond the light transceiver 51 and the light transceiver 52 to each other by being firmly contacted using a van der Waals force. FIG. 16 is a schematic diagram showing a cross-sectional structure of another optical semiconductor device according to Embodiment 5 of the invention. The other semiconductor optical device 50 shown in FIG. 16 is different from the semiconductor optical device 50 shown in FIG. 15 in that the interlayer film 113 is not provided and the light transceiver 51 and the light transceiver 52 are directly bonded to each other by utilizing a van der Waals force in a firmly contacted state.Operations and effects according to the optical semiconductor device 50 of Embodiment 5 will be described. The semiconductor optical device 50 of Embodiment 5 is obtained by adding, to the semiconductor optical device 50 of Embodiment 4 in which optical communication is established between two light transceivers 51, 52, the configuration for electrical connection for establishing electrical connection with an external system and the configuration for optical communication (external system-related optical communication unit) for establishing optical communication with an external system. As in the semiconductor optical device 50 of Embodiment 4, the optical signal 13 amitted from the light emitting unit 102, which is a planar light emitting structural unit such as a laser diode, a light emitting diode, or the like, is refracted by the Fresnel lens 61 bformed on the interlayer film 31 as an SiO2-based film, to thereby pass through the protective film 81 as an SiN film formed in a distant region in the running direction of this signal. The refractive index of the protective film 81 is 1.9, and thus the refractive index of the protective film 81 is larger than the refractive index of 1.4 of the interlayer film 31, so that at the boundary between the interlayer film 31 and the protective film 81, the optical signal is refracted further toward the central side. This prevents the optical signal 13a from being scattered and attenuated.The optical signal 13 amitted from the light emitting unit 102 passes through the interlayer film 113 made of an organic or inorganic material, and is then received by the light receiving unit 115 as a planar light receiving structural unit such as an avalanche photodiode (APD) or the like formed or mounted on the semiconductor substrate 126 of the light transceiver 52. The optical signal 13 aindicated on the light transceiver 52 first enters the planarized protection film 81 as an SiN film and is converged by the Fresnel lens 61 aformed on the interlayer film 31 as an SiO2-based film located on the semiconductor substrate 126 side as viewed from the protection film 81 and received by the light receiving unit 115. The refractive index of the protective film 81 is 1.9, and the refractive index of the interlayer film 31 is 1.4, so that the light receiving unit 115 of the light transceiver 52 can converge optical signals at angles larger than those according to a conventional APD using a single-layered SiO2 lens, thereby enhancing the light receiving sensitivity of the light receiving unit 115. Accordingly, even if the optical signal 13a is weak, the light receiving unit 115 of the light transceiver 52 can detect this signal.The optical signal 13 areceptored by the light receiving unit 115 of the light transceiver 52 is subjected to analog or digital signal processing by the integrated circuit 104 such as a signal processing circuit or the like formed on the semiconductor substrate 126, and the processed signal is transmitted as the optical signal 13 bfrom the light emitting unit 114. The optical signal 13b emitted from the light emitting unit 114 of the light transceiver 52 passes through the Fresnel lens 61b formed as an SiO2-based film on the interlayer film 31, the protective film 81 as an SiN film, and the interlayer film 113 formed of an organic or inorganic material in a direction opposite to that of the optical signal 13a, and is converged by the Fresnel lens 61a formed as an SiN film on the protective film 81 and the interlayer film 31 as an SiO2-based film in the light transceiver 51 and then accepted by the light receiving unit 103.According to the semiconductor optical device 50 of Embodiment 5, since optical communication is established between two light transceivers 51, 52 via a shortest path, it is possible to reduce the output power of each of the optical signals 13 a, 13 bto a minimum. Meanwhile, in the semiconductor optical device 50 of Embodiment 5, according to the wavelengths of the optical signals 13 a, 13 band the path, the focal lengths of the Fresnel lenses 61 a, 61 bare respectively optimally set by adjusting the film thickness of the interlayer film 31 as the SiO2-based film, the intervals between the concentric circles in the structure of each of the Fresnel lenses 61 a, 61 b, and / or the dry etching depth thereof. Further, in the optical semiconductor device 50 of Embodiment 5, the respective protective films 81 are provided in respective remote regions apart from the semiconductor substrates 121, 126 of the light transceivers 51, 52 in directions perpendicular thereto, namely, on the surfaces of the respective interlayer films 31 (their surfaces on the sides opposite to the sides facing the semiconductor substrates 121, 126), so that sufficient moisture resistance is ensured.The electrode unit 107 is formed in the light transceiver 51 so as to accomplish power supply from an external system and transmission of electrical signals to / from an external system. The electrode unit 106 formed in the light transceiver 51 is connected to the electrode unit 108 formed in the light transceiver 52. A power supply voltage and a power supply current are supplied from the electrode unit 106 as an electrode for power supply to the light transceiver 52 via the electrode unit 108. Between the electrode unit 106 as an electrode for electric signal transmission and the electrode unit 107 as an electrode for electric signal transmission, a signal unrelated to optical communication is transmitted.According to the semiconductor optical device 50 of Embodiment 5, from the light emitting unit 122 formed or mounted on the semiconductor substrate 121 of the light transceiver 51, the optical signal 13 cis transmitted to an external system in, for example, the direction indicated by an arrow 14 a, while the optical signal 13 dis accepted from the external system, for example, the direction indicated by an arrow 14 bfrom the light receiving unit 123 formed or mounted on the semiconductor substrate 121 of the light transceiver 51. In this way, according to the optical semiconductor device 50 of Embodiment 5, it is also possible to establish optical communication with the external system.In addition to having effects similar to those according to the optical semiconductor device 50 of Embodiment 4, the optical semiconductor device 50 of Embodiment 5 can establish communication with an external system(s) using an electric signal and an optical signal. Since the semiconductor optical device 50 of Embodiment 5 can establish communication with an external system(s) using an electric signal and an optical signal, although it is significantly smaller than a conventional optical module in which an optical semiconductor device handling many optical signals, a semiconductor device without handling an optical signal, and other components are modularized, it can adapt to an increase in volume of transmitted information and an acceleration in communication speed. Further, since the semiconductor optical device 50 of Embodiment 5, although small, can adapt to an increase in the volume of transmitted information and the acceleration of the communication speed, it is possible to achieve downsizing, reduction in power consumption, and cost reduction accordingly for the external system.Embodiment 6FIG. 17 is a schematic diagram showing a cross-sectional structure of a semiconductor optical device according to an embodiment 6 of the invention, and FIG. 18 is a diagram showing a plan view shape of a single-sided Fresnel lens in FIG. 17. A semiconductor optical device 50 of Embodiment 6 is an example of a semiconductor optical device provided with: a light transmitter including a light emitting unit for emitting light of a plurality of wavelengths; and a light receiver including a plurality of light receiving units corresponding to the wavelengths of the light emitted from the light transmitter. The semiconductor optical device 50 of Embodiment 6 is a semiconductor optical device including a light transmitter 53 and a light receiver 54, and wherein the light transmitter 53 and the light receiver 54 are bonded to each other using an interlayer film 113 made of an organic or inorganic material. The light transmitter 53 includes: a semiconductor substrate 131 on which an integrated circuit 104 such as a signal processing circuit or the like and an integrated circuit 105 such as a power circuit or the like are formed; a light emitting unit 132 provided (formed or mounted) on the semiconductor substrate 131 to emit optical signals 16 including optical signals of the plurality of wavelengths simultaneously or in a time division manner; an interlayer film 31 as an SiO2-based film; and a protection film 81 as an SiN film covering a single-sided Fresnel lens 133 formed on a surface of the interlayer film 31. The light emitting unit 132 is a planar light emitting structural unit such as a laser diode or the like to emit optical signals of the plurality of wavelengths simultaneously or in a time division manner. The one-side Fresnel lens 133 in the light transmitter 53 is a Fresnel lens for radiating light formed in a remote region separated from the light emitting unit 132 in a direction perpendicular thereto, namely, on the surface of the interlayer film 31 (the surface thereof on the side opposite to the side facing the semiconductor substrate 131).The one-sided Fresnel lens 133 includes four convex portions 142a, 142b, 142c, and 142d between a dotted line 143a and a dotted line 143b. The respective convex portions 142 a, 142 b, 142 c, 142 dcorrespond to shapes obtained when the convex portions 62 a, 62 b, 62 c, 62 dare modified in the Fresnel lens 61 of FIG. 6 to have open shapes instead of the ring shapes, and are formed in, for example, slit shapes as shown in FIG. 18. With respect to the adjacent convex portions, a largest level difference is exhibited at a boundary therebetween, and each of the convex portions protrudes upward (toward another side separated from the semiconductor substrate 131 in a direction perpendicular thereto) in a gradually increasing manner along a direction toward the left side in FIG. 18. In other words, each concave portion sandwiched between the convex portions is deepest at its right side in FIG. 18, and gradually becomes shallower along a direction toward the left side in FIG. 18.The light receiver 54 includes: a semiconductor substrate 134 on which an integrated circuit 104 such as a signal processing circuit or the like and an integrated circuit 105 such as a power circuit or the like are formed; a light receiving unit 135 provided (formed or mounted) on the semiconductor substrate 134 to receive a short wavelength optical signal 17 a; a light receiving unit 136 provided (formed or mounted) on the semiconductor substrate 134 to receive a long wavelength optical signal 17 b; and an interlayer film 31 as an SiO2-based film. The light receiving units 135, 136 are each a planar light receiving structural unit such as an avalanche photodiode (APD) or the like.The manufacturing steps of the light transmitter 53 are similar to the manufacturing steps described in Embodiment 1. In a manufacturing step of the single-sided Fresnel lens 133, a resist pattern is formed to have a plan-view shape matching the plan-view shape of the single-sided Fresnel lens 133 in FIG. 18 and a cross-sectional shape corresponding to a shape in the resist pattern 41 in FIG. 5 from the center of the convex portion 62 a(see FIG. 6 ) to the right side. The manufacturing steps of the light receiver 54 are similar to the manufacturing steps up to planarization of the interlayer film 31 in the manufacturing steps disclosed in Embodiment 1.In FIG. 17, an example of the semiconductor optical device 50 is shown, wherein the light transmitter 53 and the light receiver 54 are bonded to each other using the interlayer film 113 made of an organic or inorganic material. However, as shown in FIG. 19, since the surface of the light emitter 53 that is farthest from the semiconductor substrate 131 in a direction perpendicular thereto is provided by the planarized protective film 81 and the surface of the light receiver 54 that is farthest from the semiconductor substrate 134 in a direction perpendicular thereto is provided by the planarized interlayer film 31, it is allowable to directly bond the light emitter 53 and the light receiver 54 to each other by making contact with them firmly using a van der Waals force. FIG. 19 is a schematic diagram showing a cross-sectional structure of another optical semiconductor device according to Embodiment 6 of the invention. The other semiconductor optical device 50 shown in FIG. 19 is different from the semiconductor optical device 50 shown in FIG. 17 in that the interlayer film 113 is not provided and the light transmitter 53 and the light receiver are directly bonded to each other using a van der Waals force in a firmly contacted state. Note that the examples shown in FIGS. 17 and 19 are each illustrated as a case where two wavelengths are used; however, if the number of light receiving units is increased, it is also possible to apply the example to a case where multiple wavelengths are used.Operations and effects according to the optical semiconductor device 50 of Embodiment 6 will be described. Then, as shown in FIGS. 17 and 19, when the optical signals 16 including the optical signals 17 a, 17 bhaving two wavelengths are emitted from the light emitting unit 132 as a planar light emitting structural unit such as a laser diode or the like, the optical signals 17 a, 17 bare refracted by angles according to their wavelengths due to a spectroscopic effect of the single-sided Fresnel lens 133 formed on the interlayer film 31 as an SiO2-based film, so as to pass therethrough through the protective film 81 as an SiN film formed in a distant region in the running direction of each of these signals. The refractive index of the protective film 81 is 1.9, and thus the refractive index of the protective film 81 is larger than the refractive index of 1.4 of the interlayer film 31, so that at the boundary between the interlayer film 31 and the protective film 81, the optical signals are refracted further toward the central side of the one-side Fresnel lens 133 (toward the dotted line 143 aside). This makes it possible to increase the separation angle between the optical signals 17 a, 17 bof two wavelengths.The optical signals 17a, 17b separated according to their wavelengths enter the opposing light receiver 54 so that the short wavelength optical signal 17a is received by the light receiving unit 135 and the long wavelength optical signal 17b is received by the light receiving unit 136. They are subjected to analog or digital signal processing on the semiconductor substrate 134. The optical signals 17 a, 17 bof the respective wavelengths received by the light receiving units 135, 136 are subjected to analog or digital signal processing by the integrated circuit 104 such as a signal processing circuit or the like formed on the semiconductor substrate 134, and the processed signals are respectively sent electrically or optically to an external system. Note that, when the processed signal is electrically transmitted to an external system, it is transmitted from an unillustrated electrode unit 107 (see FIG. 15 ) disposed in the light receiver 54. When the processed signal is optically transmitted to an external system, it is transmitted from a light emitting unit 122, not shown, formed or mounted on the semiconductor substrate 134 (see FIG. 15 ).According to the semiconductor optical device 50 of Embodiment 6, since optical communication is established between the light transmitter 53 and the light receiver 54 via a shortest path, it is possible to reduce the output power of each of the output signals 16, 17 a, 17 bto a minimum. Meanwhile, in the semiconductor optical device 50 of Embodiment 6, according to the wavelengths of the optical signals 17 a, 17 band the path, the focal length of the single-sided Fresnel lens 133 is optimally set by adjusting the film thickness of the interlayer film 31 as the SiO2-based film, the intervals between the convex portions in the structure of the single-sided Fresnel lens 133, and / or the dry etching depth thereof. Further, in the optical semiconductor device 50 of Embodiment 6, the protective film 81 is provided in a removed region in the light emitter 53 separated from the semiconductor substrate 131 in a direction perpendicular thereto, namely, on the surface of the interlayer film 31 (the surface thereof on the side opposite to the side facing the semiconductor substrate 131), so that sufficient moisture resistance for the light emitter 53 is ensured. Further, in the optical semiconductor device 50 of Embodiment 6, a removed portion in the light receiver 54 separated from the semiconductor substrate 134 in a direction perpendicular thereto, namely, the surface of the interlayer film 31 (the surface thereof on the side opposite to the side facing the semiconductor substrate 134) is covered by the protective film 81 of the light transmitter 53 via the interlayer film 113 made of an organic or inorganic material or directly covered by the protective film 81 of the light transmitter 53, so that sufficient moisture resistance is secured for the light receiver 54.In the semiconductor optical device 50 of Embodiment 6, the optical signals 16 containing a plurality of wavelengths and emitted from the light emitting unit 132 of the light transmitter 53 are spectrally diffused by the Fresnel lens 133 formed on the interlayer film 31 and received by the respective light receiving units 135, 136 corresponding to the wavelengths in the light receiver 54, and then subjected to signal processing. Thus, the number of channels of communication using optical signals is increased to a multiple thereof according to the number of wavelengths, resulting in an increased communication speed. Further, since the number of channels for optical signal communication is increased to a multiple thereof according to the number of wavelengths, according to the semiconductor optical device 50 of Embodiment 6, it is possible to achieve downsizing and cost reduction compared with the conventional device. Moreover, the semiconductor optical device 50 of Embodiment 6 can prevent the optical signals 16, 17 a, 17 bfrom being diffused and attenuated, so that it is also possible to achieve reduction in power consumption.According to the semiconductor optical device 50 of Embodiment 6, since, as in Embodiment 4, the light transmitter 53 and the light receiver 54 are bonded together as two semiconductor devices and optical signals are used for communication from the light transmitter 53 to the light receiver 54, it becomes possible to reduce the number of components and significantly reduce the area. In the light transmitter 53, the one-sided Fresnel lens 133 was formed by a wafer manufacturing process (in the wafer manufacturing steps) on a far side of the light emitting unit 132 for transmitting the optical signals separately from the semiconductor substrate 131 in the direction perpendicular thereto. This makes it possible to achieve downsizing, reduction in power consumption, and cost reduction for the light transmitter 53 as the semiconductor optical device. Further, in the light receiver 54, a lens was not formed on the surface of the interlayer film 31 (the surface thereof on the side opposite to the side facing the semiconductor substrate 134) located on another side of the light receiving units 135, 136 for receiving optical signals separately from the semiconductor substrate 134 in a direction perpendicular thereto. This makes it possible to achieve downsizing, reduction in power consumption, and cost reduction for the light receiver 54 as a semiconductor optical device. Moreover, for the semiconductor optical device 50 of Embodiment 6 in which the light transmitter 53 and the light receiver 54 are bonded together as two semiconductor devices, it also becomes possible to achieve downsizing, reduction in power consumption, and cost reduction.Embodiment 7FIG. 20 is a schematic diagram showing a cross-sectional structure of an optical semiconductor device according to an embodiment 7 of the invention. FIGS. 21 and 22 are diagrams each illustrating a wafer manufacturing step for the optical semiconductor device of FIG. 20. FIG. 23 is a diagram showing a plan view shape of a Fresnel lens in FIG. 20. A semiconductor optical device 50 of Embodiment 7 is an example of a highly functional semiconductor optical device such as an infrared sensor or the like that includes an integrated circuit, an infrared light receiving unit, and a Fresnel lens. The semiconductor optical device 50 of Embodiment 7 includes: a semiconductor substrate 151 on which an integrated circuit 104 such as a signal processing circuit or the like and an integrated circuit 105 such as a power circuit or the like are formed; an infrared light receiving unit 152 formed on the semiconductor substrate 151; an interlayer film 31 as an SiO2-based film; a Fresnel lens 171 made of polysilicon or amorphous silicon provided on a surface of the interlayer film 31; and a protective film 81 as an SiN film covering the Fresnel lenses 171. The infrared light receiving unit 152 is a planar light receiving structural unit for receiving infrared light. The infrared light receiving unit for receiving an infrared signal is a light receiving unit for receiving an optical signal of infrared light.Wafer manufacturing steps for the optical semiconductor device 50 of Embodiment 7 will be described. As shown in FIG. 21, the infrared light receiving unit 152 is formed on the semiconductor substrate 151, on which the integrated circuit 104 such as a signal processing circuit or the like and the integrated circuit 105 such as a power circuit or the like are formed. The semiconductor substrate 151 on which the integrated circuits 104, 105 and the infrared light receiving unit 152 are formed is a substrate before lens formation. Thereafter, the planarized interlayer film 31 is formed as an SiO2-based film as described in Embodiment 1, and a silicon film 153 formed of polysilicon or amorphous silicon and provided as a material for the Fresnel lens 171 is formed on the surface of the interlayer film 31. The film thickness of the silicon film 153 ranges from 0.1 to 1.0 μm.As shown in FIG. 22, in order to form the Fresnel lens 171 on the surface of the silicon film 153, a resist pattern 161 for forming the Fresnel lens is developed by a multi-exposure photolithography technique using an electron beam (EB) method. The resist pattern 161 is arranged so that convex portions 172a, 172b, 172c, and 172d are left. Further, the resist pattern 161 is formed to match the shapes of concave portions between respective adjacent convex portions; for example, it is formed to have stepped shapes in which the thickness corresponding to a low height part in the convex portion is thin, whereas the thickness corresponding to a high height part in the convex portion is thick. The resist pattern 161 is further arranged so that a portion of the silicon film 153 outside the region of the Fresnel lens 171 is removed. As shown in FIG. 22, the convex portions 172a, 172b, 172c, 172d of the Fresnel lens 171 are formed by a dry etching method. FIG. 22 shows convex portions of the Fresnel lens 171 during etching, and shows a state in which the resist pattern 161 remains on the convex portions of the Fresnel lens 171 after the resist portions for the respective low-height portions in the convex portions gradually disappear with the progress of etching by etching ions 15 for the convex portions.The shape in plan view of the Fresnel lens 171 is, for example, a concentric circular shape as shown in FIG. 23. Generally, as the shape in plan view of the Fresnel lens 171, a concentric circular shape as shown in FIG. 23 is used. Instead, the shape in plan view of the Fresnel lens 171, similar to FIG. 9 or 10, may be a square shape provided with curvatures at four corners or a rectangular shape provided with curvatures at four corners, and may be another shape. The shape of the Fresnel lens 171 is selected according to the shape of the infrared light receiving unit 152. The resist pattern 161 is formed to have fine widths of a residual resist corresponding to the shape in plan view of the Fresnel lens 171. The resist pattern 161 for forming the shape in plan view of FIG. 23 is formed such that a width of a residual resist for forming the central convex portion 172 ais wider than a width of a residual resist for forming each of the other convex portions 172 b, 172 c, and 172 d, and the width of a residual resist for forming each of the convex portions 172 b, 172 c, and 172 dis gradually narrowed in this order.After completion of the etching step for the Fresnel lens 171 and removal of the resist pattern 161, in order to ensure moisture resistance, the protective film 81 which is an SiN film having a refractive index larger than that of the interlayer film 31 as an SiO2-based film and having a film thickness of 1.0 to 3.0 μm is deposited by a CVD method or the like to cover the Fresnel lens 171 and the interlayer film 31, and thereafter planarized. Note that the Fresnel lens 171 has been described, taking a case of using a silicon element such as using a film of polysilicon or amorphous silicon; however, a material consisting of a germanium element or a compound of germanium and silicon may be used instead.Operations and effects according to the optical semiconductor device 50 of Embodiment 7 will be described. An infrared signal 173 ahaving a wavelength λ of 1.1 to 1.5 μm enters the planarized protection film 81 as a SiN film, so that an infrared signal 173 bconverified by the Fresnel lens 171 formed on the interlayer film 31 as a SiO2-based film under the protection film 81 is received by the infrared light receiving unit 152. The refractive index of the protective film 81 is 1.9, and the refractive index of the interlayer film 31 is 1.4, so that the semiconductor optical device 50 of Embodiment 7 can converge infrared signals at large angles and thus detect a weak signal. Further, according to the semiconductor optical device 50 of Embodiment 7, since an unwanted infrared signal having a wavelength λ other than 1.1 to 1.5 μm is reflected or absorbed away by the Fresnel lens 171, the unwanted infrared signal is not received by the infrared light receiving unit 152, so that the light receiving sensitivity for the infrared signal 173 bhaving a specific wavelength, namely, having a wavelength λ of 1.1 to 1.5 μm, is enhanced.The received infrared signal 173 bis subjected to analog or digital signal processing by the integrated circuit 104 formed on the semiconductor substrate 151 such as a signal processing circuit or the like, so that the presence, distance, and position of an infrared light emitting object are determined by calculation, and then the information on the presence, distance, and position of the object is transmitted to another control system outside the semiconductor optical device 50. Meanwhile, according to the wavelength of the infrared signal 173 a, 173 b, the focal length of the Fresnel lens 171 is set on the basis of the film thickness of the interlayer film 31 as the SiO2-based film, the intervals between the concentric circles in the structure of the Fresnel lens 171, and the dry etching depth thereof. Further, in the optical semiconductor device 50 of Embodiment 7, the protective film 81 is provided on the upper surface thereof, so that sufficient moisture resistance is secured.The conventional infrared sensor does not use an infrared light collecting lens or needs to have a module configuration in which a self-contained lens is assembled with a self-contained housing. In contrast, according to the semiconductor optical device 50 of Embodiment 7, the Fresnel lens 171 is formed in the wafer manufacturing steps for the semiconductor optical device including the infrared light receiving unit 152, so that the manufacturing steps thereof can be simplified and the number of components thereof can be reduced to thereby achieve downsizing as compared with the conventional device. According to the semiconductor optical device 50 of Embodiment 7, since the Fresnel lens 171 is formed in the wafer manufacturing steps for the semiconductor optical device including the infrared light receiving unit 152, it becomes possible to eliminate such a step of assembling a self-contained lens with a self-contained case and thus to reduce the number of manufacturing steps. According to the optical semiconductor device 50 of Embodiment 7, since the number of components and the number of manufacturing steps are reduced, it becomes possible to achieve cost reduction. Moreover, according to the semiconductor optical device 50 of Embodiment 7, since unwanted infrared light is reflected or absorbed, it also becomes possible to achieve an increase in sensitivity and a reduction in power consumption.Embodiment 8FIG. 24 is a diagram showing a plan shape of a Fresnel lens according to Embodiment 8 of the invention, and FIG. 25 is a diagram showing a plan shape of a lens array according to Embodiment 8 of the invention. FIG. 26 is a schematic diagram showing a plan view of an optical semiconductor device according to Embodiment 8 of the invention, and FIG. 27 is a schematic diagram showing a cross-sectional structure of the optical semiconductor device of FIG. 26. FIG. 27 is a schematic diagram showing a cross-sectional structure cut along A-A in FIG. 26. The semiconductor optical device 50 of Embodiment 8 is an example of a semiconductor optical device represented by solar battery cells or the like, and includes an array of Fresnel lenses each having a regular hexagonal shape. The semiconductor optical device 50 of Embodiment 8 includes: a solar battery cell substrate 191 as a semiconductor substrate; light receiving units 192 provided (formed) on the solar battery cell substrate 191 to receive sunlight; an interlayer film 31 as an SiO2-based film; Fresnel lenses 193 provided on the surface of the interlayer film 31; and a protective film 81 as an SiN film covering the Fresnel lenses 193. In the optical semiconductor device 50 of Embodiment 8, the light receiving units 192 are patterned on the surface of the solar battery cell substrate 191 such that the light receiving units 192 are respectively placed under the Fresnel lenses 193 each having a regular hexagonal shape. The light receiving units 192 are each a planar light receiving structural unit such as an avalanche photodiode (APD) or the like.The Fresnel lens 193 has a periphery 195 whose shape in plan view is a regular hexagon, and includes four convex portions 194 a, 194 b, 194 c, and 194 dformed in a circular and concentric manner. The convex portions 194 a, 194 b, 194 c, 194 dare similar to the convex portions 62 a, 62 b, 62 c, 62 din the Fresnel lens 61 of Embodiment 1. The manufacturing steps of the optical semiconductor device 50 of Embodiment 8 are similar to the manufacturing steps described in Embodiment 1.Operations and effects according to the optical semiconductor device 50 of Embodiment 8 will be described. For a solar battery, it is necessary to increase the efficiency of sunlight incidence. However, the basic structure of the Fresnel lens illustrated in FIG. 1 is a concentric ring structure, and according to the shape in plan view of such a concentric ring, it cannot completely cover a planar surface. Thus, in the case where Fresnel lenses for the solar battery cells are used as the semiconductor optical device for receiving light in the solar battery, the shape per unit of a Fresnel lens is set to a regular hexagonal shape as shown in FIG. 24, and the Fresnel lenses 193 each having the regular hexagonal shape are staggered as shown in FIG. 25 to an array shape. This makes it possible to make maximum use of the area of the solar battery cells with respect to the area of the solar battery cells, namely, to increase the filling ratio (filling rate) of the basic structure including the light receiving unit 192 and the Fresnel lens 193. A lens array 196 shown in FIG. 25 is an example in which thirteen Fresnel lenses 193 are arranged.As shown in FIG. 27, sunlight 174 aenters the planarized protection film 81 as a SiN film, so that sunlight 174 bconvergeed by the Fresnel lens 193 formed on the interlayer film 31 as a SiO2-based film under the protection film 81 is received by the light receiving unit 192. The refractive index of the protective film 81 is 1.9, and the refractive index of the interlayer film 31 is 1.4, so that the semiconductor optical device 50 of Embodiment 8 can converge sunlight at angles larger than those according to conventional solar battery cells without using lenses. Moreover, according to the semiconductor optical device 50 of Embodiment 8, the solar battery cell solar absorption efficiency is enhanced in such a manner that the focal length of the Fresnel lens 193 is adjusted according to the wavelength of the sunlight 174 a, 174 bon the basis of the film thickness of the interlayer film 31 as the SiO2-based film, the intervals between the concentric circles in the structure of the Fresnel lens 193, and the dry etching depth thereof. Further, in the optical semiconductor device 50 of Embodiment 8, the protective film 81 is provided on the upper surface thereof, so that sufficient moisture resistance is secured.It is noted that the description has been made about solar battery cells as an example of the semiconductor optical device 50 including an array of Fresnel lenses each having a regular hexagonal shape; however, the plurality of Fresnel lenses may be laid out into an array shape above light receiving units other than the light receiving units 192 for receiving sunlight, such as light receiving units, to receive other light such as an optical signal(s), an infrared signal(s), or the like. A semiconductor optical device 50 in which the light receiving units for receiving an optical signal (signals), an infrared signal (infrared signals), or the like are respectively disposed under the Fresnel lenses 193 each having a regular hexagonal shape also provides effects equivalent to those according to the semiconductor optical device 50 of Embodiment 8.According to the optical semiconductor device 50 of Embodiment 8, since the Fresnel lenses 193 each having a regular hexagonal shape are formed in the wafer manufacturing steps for the solar battery cells, it is possible to efficiently use the light receiving area on the surface of the solar battery cells. When the configuration of the lens assembly according to Embodiment 8 is applied to a solar battery, it is possible to increase the light collection efficiency of sunlight per area, thus making it possible to increase the power conversion efficiency of the solar battery. Note that, according to a semiconductor optical device 50 in which a plurality of light receiving units for receiving optical signals, infrared signals, or the like and a plurality of light emitting units for emitting optical signals, infrared signals, or the like are arranged under their respective Fresnel lenses 193 each having a regular hexagonal shape, it is possible to increase the filling ratio (filling rate) of the base structure including the light receiving unit and the Fresnel lens and the base structure including the light emitting unit and the Fresnel lens, and thus to reduce the area of the semiconductor optical device.DESCRIPTION OF THE REFERENCE NUMERALS8 a, 8 b:optical signal, 9 a, 9 b:optical signal, 11: semiconductor substrate, 12: light receiving unit, 13 a, 13 b, 13 c, 13 d:optical signal, 16: optical signal, 17 a, 17 b:optical signal, 21: interlayer film, 31: interlayer film, 50: semiconductor optical device, 51: light transceiver, 52: light transceiver, 53: light transmitter, 54: light receiver, 61, 61 a, 61 b:Fresnel lens, 71: protective film, 81: protective film, 91: light emitting unit, 101: semiconductor substrate, 102: light emitting unit, 103: light receiving unit, 104: integrated circuit, 105: integrated circuit, 113: interlayer film, 114: light emitting unit, 115: light receiving unit, 121: semiconductor substrate, 122: light emitting unit (external system related light emitting unit), 123: light receiving unit (external system related light receiving unit), 131: semiconductor substrate, 132: light emitting unit, 133: one-side Fresnel lens, 135: light receiving unit, 136: light receiving unit, 151: semiconductor substrate, 152: infrared light receiving unit, 171: Fresnel lens, 173a, 173b: infrared signal (optical signal), 174a, 174b: sunlight, 191: solar battery cell substrate (semiconductor substrate), 192: light receiving unit, 193: Fresnel lens

Claims

A semiconductor optical device (50) comprising: a first light transceiver (51) formed with a first semiconductor substrate (111), and a second light transceiver (52) formed with a second semiconductor substrate (112), and configured to establish communication by optical signals mutually between the first and second transceivers (51, 52), wherein: the first light transceiver (51) comprises: the first semiconductor substrate (111); a light receiving unit (103) for receiving an optical signal (13a, 13b), and a light emitting unit (102) for emitting the optical signal (13a, 13b) formed on the first semiconductor substrate (111); a first interlayer film (31) covering the first semiconductor substrate (111), the light receiving unit (103) and the light emitting unit (102); Fresnel lenses (61a, 61b) through which the optical signals (13a, 13b) respectively formed for the light receiving unit (103) and the light emitting unit (102) can pass and which are formed on a planarized surface of the first interlayer film (31) located on its side opposite to the first semiconductor substrate (111); and a first protective film (81) covering the Fresnel lenses (61a, 61b) and the first interlayer film (31) whose refractive index is larger than that of the first interlayer film (31) and whose surface located on its side opposite to the first interlayer film (31); and the second light transceiver (52) comprises: the second semiconductor substrate (112); a light receiving unit (115) for receiving an optical signal (13a, 13b) and a light emitting unit (114) for emitting the optical signal (13a, 13b) formed on the second semiconductor substrate (112); a second interlayer film (31) covering the second semiconductor substrate (112), the light receiving unit (115), and the light emitting unit (114); Fresnel lenses (61a, 61b) through which the optical signals (13a, 13b) respectively formed for the light receiving unit (115) and the light emitting unit (114) can pass and which are formed on a planarized surface of the second interlayer film (31) located on its side opposite to the second semiconductor substrate (112); and a second protective film (81) covering the fresnel lenses (61a, 61b) and the second interlayer film (31) whose refractive index is larger than that of the second interlayer film (31) and whose surface located on its side opposite to the second interlayer film (31); the light receiving unit (103) in the first light transceiver (51) and the light emitting unit (114) in the second light transceiver (52) are placed to face each other, and the light emitting unit (102) in the first light transceiver (51) and the light receiving unit (115) in the second light transceiver (52) are placed to face each other; the first protective film (81) in the first light transceiver (51) and the second protective film (81) in the second light transceiver (52) are bonded to one another directly or via a third interlayer film (113), the first light transceiver (51) has a first integrated circuit (104) formed on the first semiconductor substrate (111), the second light transceiver (52) has a second integrated circuit (104) formed on the second semiconductor substrate (112); and - the first integrated circuit (104) and the second integrated circuit (104) are configured to perform signal processing and generate an electric signal, respectively, after converting the optical signal (13a, 13b) received by the corresponding light-receiving unit (103, 115) into an electric signal, which serves as a basis for the optical signal (13a, 13b) to be emitted by the corresponding light-emitting unit (102, 114).The semiconductor optical device (50) according to claim 1, wherein the first light transceiver (51) has an external system-related optical communication unit, - the external system-related light receiving unit (123) is for receiving an optical signal (13d) from an external system other than the second light transceiver (52), or - an external system-related light emitting unit (122) is for emitting an optical signal (13c) to the external system.The semiconductor optical device (50) according to claim 1, wherein the first light transceiver (51) comprises: an external-system-related light receiving unit (123) for receiving an optical signal (13d) from an external system other than the second light transceiver (52); and an external-system-related light emitting unit (122) for emitting an optical signal (13c) to the external system.The semiconductor optical device (50) according to claim 2, wherein: - the external-system-related optical communication unit is the external-system-related light receiving unit (192); - a plurality of external-system-related light receiving units (192), each being the external-system-related light receiving unit (192), are formed on the first semiconductor substrate (111); - the Fresnel lens (193) is further formed for each of the external-system-related light receiving units (192), the Fresnel lens (193) having a periphery of a regular hexagonal shape in a plane parallel to the first semiconductor substrate (111); and - the Fresnel lenses (193) adjacent to each other are arranged such that their peripheries are in contact with each other.The semiconductor optical device (50) according to claim 3, wherein: - a plurality of external-system-related light receiving units (192), each being the external-system-related light receiving unit (192), are formed on the first semiconductor substrate (111); - the Fresnel lens (193) is further formed for each of the external-system-related light receiving units (192), the Fresnel lens (193) having a periphery having a regular hexagonal shape in a plane parallel to the first semiconductor substrate (111); and - the mutually adjacent Fresnel lenses (193) are arranged such that the peripheries thereof are in contact with each other.A semiconductor optical device (50) comprising: - a light transmitter (53) for emitting simultaneously or in a time-division manner, respectively, optical signals (17a, 17b) containing a plurality of wavelengths; and - a light receiver (54) placed facing said light transmitter (53) for receiving said optical signals (17a, 17b) from said light transmitter (53) according to their respective wavelengths; wherein: - said light transmitter (53) comprises: - a first semiconductor substrate (131); - a light emitting unit (132) formed on said first semiconductor substrate (131) for emitting said optical signals (17a, 17b); - a first interlayer film (31) covering said first semiconductor substrate (131) and said light emitting unit (132); a single-sided Fresnel lens (133) through which the optical signals (17a, 17b) can pass, which is formed on a planarized surface of the first interlayer film (31) located on its side facing away from the first semiconductor substrate (131); and a first protective film (81) covering the single-sided Fresnel lens (133) and the first interlayer film (31), whose refractive index is greater than that of the first interlayer film (31) and whose surface located on its side facing away from the first interlayer film (31) is planarized; the light receiver (54) comprises: a second semiconductor substrate (134); a plurality of light receiving units (135, 136) formed on the second semiconductor substrate (134) for receiving the optical signals (17a, 17b) whose refraction angles have been set differently according to their respective wavelengths by the one-sided Fresnel lens (133) of the light transmitter (53); and a second interlayer film (31) covering the second semiconductor substrate (134) and the plurality of light receiving units (135, 136); and the first protective film (81) in the light transmitter (53) and the second interlayer film (31) in the light receiver (54) are bonded to each other directly or via a third interlayer film (113).

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