Abstract:
According to this invention, light incident on a microlens at a large incident angle can be efficiently guided to a photo-electric converting portion in a solid state image sensor. In a solid state image sensor having a plurality of pixels, each of the plurality of pixels includes a microlens which condenses light, a photo-electric converting portion which photoelectrically converts light condensed by the microlens, a metal electrode layer which is interposed between the microlens and the photo-electric converting portion and has an opening at a position corresponding to the optical path of light traveling from the microlens toward the photo-electric converting portion, and a transparent film layer which is interposed between the microlens and the photo-electric converting portion and has a convex lens-shaped portion that is convex on the microlens side. At least part of the convex lens-shaped portion in the direction of thickness extends into the opening formed in the metal electrode layer.

Description:
FIELD OF THE INVENTION  
       [0001]     The present invention relates to a technique of increasing the light intake efficiency of a solid state image sensor used in an image capturing apparatus such as a digital still camera.  
       BACKGROUND OF THE INVENTION  
       [0002]     These days, the prices of digital still cameras continue to drop. One reason for this is that the chip size of a solid state image sensor is becoming small. As the chip size of the solid state image sensor decreases, an image sensing unit including a photographing optical system becomes small. For further downsizing, the photographing optical system itself is made compact. In order to downsize the photographing optical system, the exit pupil of the photographing optical system must be arranged close to the solid state image sensor. As a result, the inclination angle (incident angle), to the optical axis, of light incident on the periphery of the input portion of the solid state image sensor becomes large. A large incident angle of light incident on the solid state image sensor inhibits light from reaching a photo-electric converting portion.  
         [0003]     To prevent this problem, for example, in a solid state image capturing apparatus disclosed in Japanese Patent Laid-Open No. 11-274443, a planoconvex lens is interposed between the on-chip microlens and photo-electric converting portion of the solid state image capturing apparatus so as to be convex on the side of the photo-electric converting portion. This structure can increase the light intake efficiency at a wide light incident angle even in a solid state image capturing apparatus having a small-area photo-electric converting portion.  
         [0004]     Japanese Patent Laid-Open No. 2000-164839 discloses a solid state image capturing apparatus in which a convex lens is arranged immediately above the photo-electric converting portion.  
         [0005]     However, in the solid state image capturing apparatus disclosed in Japanese Patent Laid-Open No. 11-274443, the planoconvex lens interposed between the on-chip microlens and the photo-electric converting portion is convex on the side of the photo-electric converting portion. Part of light reaching at a large incident angle is totally reflected by the convex lens portion, and light cannot be effectively guided to the photo-electric converting portion.  
         [0006]     As one method of preventing total reflection by the convex lens portion, a planoconvex lens  40  which is convex on the side of an on-chip microlens  25  is interposed between the on-chip microlens  25  and a photo-electric converting portion  11 , as shown in  FIG. 9  which is a sectional view showing a solid state image sensor  200 . If the planoconvex lens  40  is formed after a metal electrode layer  31  and protective layer  41  are formed, it projects from the protective layer  41  toward the on-chip microlens  25 . The distance between the on-chip microlens  25  and the planoconvex lens  40  becomes long, increasing the distance between the on-chip microlens  25  and the photo-electric converting portion  11 . It becomes difficult to guide light at a large incident angle to the photo-electric converting portion  11 .  
         [0007]     In the solid state image capturing apparatus disclosed in Japanese Patent Laid-Open No. 2000-164839, the convex lens is formed immediately above the photo-electric converting portion, i.e., near the photo-electric converting portion. The convex lens hardly contributes to condensing light incident on the photo-electric converting portion.  
       SUMMARY OF THE INVENTION  
       [0008]     The present invention has been made to overcome the conventional drawbacks, and has as its object to efficiently guide light incident on a microlens at a large incident angle to a photo-electric converting portion in a solid state image sensor.  
         [0009]     In order to solve the above problems and achieve the above object, according to the first aspect of the present invention, a solid state image sensor having a plurality of pixels is characterized in that each of the plurality of pixels comprises a microlens which condenses light, a photo-electric converting portion which photoelectrically converts light condensed by the microlens, metal layers each of which is interposed between the microlens and the photo-electric converting portion and has an opening at a position corresponding to an optical path of light traveling from the microlens toward the photo-electric converting portion, and a transparent film layer which is interposed between the microlens and the photo-electric converting portion and has a convex lens-shaped portion that is convex on a side of the microlens, and at least part of the convex lens-shaped portion in a direction of thickness extends into the opening formed in at least one metal layer among the metal layers.  
         [0010]     According to the second aspect of the present invention, a method of manufacturing a solid state image sensor comprises a photo-electric converting portion formation step of forming, on a silicon substrate, a photo-electric converting portion which photoelectrically converts incident light, a metal layer formation step of forming, above the photo-electric converting portion, a metal layer having an opening at a position corresponding to an optical path of light incident on the photo-electric converting portion, a transparent film layer formation step of forming, on the metal layer, a transparent film layer having, at a position corresponding to the opening, a convex lens-shaped portion which is convex in a direction opposite to the photo-electric converting portion, so as to make at least part of the convex lens-shaped portion in a direction of thickness extend into the opening, and a microlens formation step of forming, above the transparent film layer, a microlens which condenses light to the photo-electric converting portion.  
         [0011]     Other objects and advantages besides those discussed above shall be apparent to those skilled in the art from the description of a preferred embodiment of the invention which follows. In the description, reference is made to accompanying drawings, which form a part hereof, and which illustrate an example of the invention. Such example, however, is not exhaustive of the various embodiments of the invention, and therefore reference is made to the claims which follow the description for determining the scope of the invention. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0012]      FIG. 1  is a schematic side sectional view showing a CMOS solid state image sensor according to the first embodiment;  
         [0013]      FIGS. 2A  to  2 K are sectional views for explaining a process of manufacturing the CMOS solid state image sensor according to the first embodiment;  
         [0014]      FIGS. 3L  to  3 P are sectional views for explaining the process of manufacturing the CMOS solid state image sensor according to the first embodiment;  
         [0015]      FIG. 4  is a schematic side sectional view showing a CMOS solid state image sensor according to the second embodiment;  
         [0016]      FIGS. 5A  to  5 L are sectional views for explaining a process of manufacturing the CMOS solid state image sensor according to the second embodiment;  
         [0017]      FIGS. 6M  to  6 Q are sectional views for explaining the process of manufacturing the CMOS solid state image sensor according to the second embodiment;  
         [0018]      FIG. 7  is a schematic plan view showing one pixel of the CMOS solid state image sensor according to the second embodiment;  
         [0019]      FIG. 8  is a schematic side sectional view showing a modification of the CMOS solid state image sensor; and  
         [0020]      FIG. 9  is a schematic side sectional view showing a CMOS solid state image sensor. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0021]     Preferred embodiments of the present invention will be described in detail below with reference to the accompanying drawings.  
       First Embodiment  
       [0022]      FIGS. 1, 2A  to  2 K, and  3 L to  3 P are views showing a solid state image sensor according to the first embodiment of the present invention.  FIG. 1  is a schematic side sectional view showing a CMOS solid state image sensor.  FIGS. 2A  to  2 K and  3 L to  3 P are sectional views for explaining a process of manufacturing the CMOS solid state image sensor.  
         [0023]     The structure of the CMOS solid state image sensor according to the first embodiment will be explained with reference to  FIG. 1 .  
         [0024]     A solid state image sensor used for a digital camera or the like is made up of several million pixels.  FIG. 1  shows the section of one pixel of a solid state image sensor  1 .  
         [0025]     Light incident on the solid state image sensor  1  is condensed by an on-chip microlens  25 . Light passes through a planarization layer  24 , color filter layer  23 , planarization layer  22 , silicon nitride film layer  40 , and interlayer dielectric film layers  21  and  20 . Then, light is guided to a photo-electric converting portion  11  formed in a silicon substrate  10 .  
         [0026]     In  FIG. 1 , reference numeral  12  denotes a polysilicon electrode serving as a first electrode for transferring charges generated in the photo-electric converting portion  11 . Second and third electrodes  30  and  31  for selectively outputting transferred charges outside the solid state image sensor are respectively formed on the interlayer dielectric film layers  20  and  21 . The second and third electrodes  30  and  31  are generally formed from a metal such as aluminum. Reference numeral  60  denotes a via which connects the second and third electrodes  30  and  31 .  
         [0027]     In the solid state image sensor  1  according to the first embodiment, the silicon nitride film layer  40  covers the third electrode  31  in order to function as a conventional protective layer, too. At an opening  31   a  of the metal electrode layer  31 , a lens portion  40   a  which is convex on the light incident side is formed in a region where light condensed by the on-chip microlens  25  passes. Light condensed by the on-chip microlens  25  is deflected toward the photo-electric converting portion  11  by the convex lens portion  40   a  of the silicon nitride film layer  40 . Even light incoming at a large incident angle to the convex lens portion  40   a  can be efficiently guided to the photo-electric converting portion  11 . Since the convex lens portion  40   a  is convex on the light incident side, no total reflection of incident light occurs on the surface of the convex lens.  
         [0028]     A thickness t 1  of the convex lens portion  40   a  of the silicon nitride film layer  40  is set almost equal to a thickness ta of the third electrode  31 . Hence, the flatness is good, which facilitates planarization processing after the convex lens portion  40   a  of the silicon nitride film layer  40  is formed.  
         [0029]      FIGS. 2A  to  2 K and  3 L to  3 P are sectional views for explaining a process of manufacturing the CMOS solid state image sensor  1  according to the first embodiment.  FIGS. 2A  to  2 K and  3 L to  3 P illustrate the sectional structure of one pixel around the center of the frame of the solid state image sensor  1 .  
         [0030]     A silicon substrate  10  is thermally oxidized to form a silicon oxide film SiO (not shown) on the surface of the silicon substrate  10 . In order to form a photo-electric converting region in the silicon substrate  10 , a photoresist  50  is applied, exposed via a photomask of a predetermined pattern, and developed. For a positive photoresist, development processing dissolves the photoresist  50  in a region irradiated with light, i.e., a region  50   a  corresponding to the photo-electric converting region. As shown in  FIG. 2A , part of the silicon oxide film SiO is exposed. Ions are implanted into the silicon substrate  10  to form a photo-electric converting portion  11 .  
         [0031]     After the photo-electric converting portion  11  is formed in the silicon substrate  10 , the process advances to a step of forming, on the surface of the silicon substrate  10 , a first electrode  12  for transferring charges generated in the photo-electric converting portion  11 .  
         [0032]     A photoresist  51  is applied to the surface of the silicon substrate  10 , covered with a photomask (not shown), and exposed. The photomask is designed to transmit light in a region corresponding to the first electrode  12  which covers part of the photo-electric converting portion  11 , and shield light in the remaining region. By developing the photoresist  51 , the photoresist  51  in a region irradiated with light, i.e., a region  51   a  corresponding to the first electrode  12  dissolves. As shown in  FIG. 2B , part of the silicon oxide film SiO is exposed. As shown in  FIG. 2C , a polysilicon film  12   a  is formed, and the photoresist  51  is stripped to form the first electrode  12 .  
         [0033]     After the first electrode  12  is formed, a first interlayer dielectric film layer  20  for forming a second electrode  30  is formed and planarized, as shown in  FIG. 2D . The first interlayer dielectric film layer  20  is formed from a silicon oxide film SiO 2  at a refractive index of about 1.46.  
         [0034]     Then, the process advances to a step of forming a second electrode  30 .  
         [0035]     A photoresist  52  is applied, covered with a photomask corresponding to the pattern of the second electrode  30 , exposed, and developed. By developing the photoresist  52 , the photoresist  52  in a region irradiated with light, i.e., a region  52   a  corresponding to the second electrode  30  dissolves. As shown in  FIG. 2E , part of the first interlayer dielectric film layer  20  is exposed.  
         [0036]     Aluminum Al is deposited by a CVD apparatus or the like, and the photoresist  52  is stripped to form the second electrode  30 . As shown in  FIG. 2F , a second interlayer dielectric film layer  21  for forming a third electrode  31  is formed from a silicon oxide film SiO 2  on the second electrode  30 .  
         [0037]     Thereafter, the process advances to a step of forming a via  60  for connecting the second and third electrodes  30  and  31 .  
         [0038]     A photoresist  53  is applied, covered with a photomask corresponding to the position of the via  60 , exposed, and developed. By developing the photoresist  53 , the photoresist  53  in a region irradiated with light, i.e., a region  53   a  corresponding to the via  60  dissolves to expose part of the second interlayer dielectric film layer  21 . Dry etching is performed to form the via  60  in the second interlayer dielectric film layer  21 , as shown in  FIG. 2G . A metal plug  60   a  is buried in the via  60 .  
         [0039]     The process advances to a step of forming a third electrode  31 .  
         [0040]     A photoresist  54  is applied, covered with a photomask corresponding to the pattern of the third electrode  31 , exposed, and developed. By developing the photoresist  54 , the photoresist  54  in a region irradiated with light, i.e., a region  54   a  corresponding to the third electrode  31  dissolves to expose part of the second interlayer dielectric film layer  21 , as shown in  FIG. 2H .  
         [0041]     Aluminum Al is deposited by the CVD apparatus or the like, and the photoresist  54  is stripped to form the third electrode  31 , as shown in  FIG. 2I .  
         [0042]     The process advances to a step of forming a silicon nitride film layer  40  at a predetermined thickness so as to function as a protective layer, too, and forming, in the opening  31   a  of the third electrode  31 , a convex lens portion  40   a  for increasing the condensing efficiency.  
         [0043]     First, the silicon nitride film layer  40  is formed at a predetermined thickness on the third electrode  31 .  
         [0044]     Then, in order to form the convex lens portion  40   a  in the opening  31   a  of the third electrode  31 , a photoresist  55  is applied onto the silicon nitride film layer  40  and planarized, as shown in  FIG. 2J . As shown in  FIG. 2K , the photoresist  55  is exposed and developed via a photomask for forming a convex lens.  
         [0045]     After the photoresist  55  in a region  55   a  corresponding to the opening  31   a  of the electrode  31  is formed into a predetermined convex lens shape, dry etching is performed to transfer the convex lens shape of the photoresist  55  to the silicon nitride film layer  40 , as shown in  FIG. 3L . At this time, the vertex of the convex lens portion  40   a  formed in the silicon nitride film layer  40  is designed on the light incident side opposite to the surface of the third electrode  31 . The silicon nitride film layer  40  covers the third electrode  31  and interlayer dielectric film layer  21 , and functions as a protective layer.  
         [0046]     As shown in  FIG. 3M , a planarization layer  22  for forming a color filter layer  23  is formed. At this time, the flatness is relatively good because the silicon nitride film layer  40  is buried in the opening  31   a  of the third electrode  31 . The planarization layer  22  suffices to be thin, which contributes to an increase in light intake efficiency.  
         [0047]     As shown in  FIG. 3N , the color filter layer  23  is formed, and a planarization layer  24  for forming an on-chip microlens is formed on the color filter layer  23 .  
         [0048]     As shown in  FIG. 30 , a photoresist  56  for forming the on-chip microlens  25  is formed, covered with a photomask corresponding to the shape of the on-chip microlens, exposed, and developed ( FIG. 30 ).  
         [0049]     The photoresist  56  is thermally fused to form the on-chip microlens  25 .  
       Second Embodiment  
       [0050]      FIGS. 4, 5A  to  5 L,  6 M to  6 Q, and  7  are views showing a solid state image sensor according to the second embodiment of the present invention.  FIG. 4  is a schematic side sectional view showing a CMOS solid state image sensor.  FIGS. 5A  to  5 L and  6 M to  6 Q are sectional views for explaining a process of manufacturing the CMOS solid state image sensor.  FIG. 7  is a schematic plan view showing one pixel of the CMOS solid state image sensor. In the second embodiment, the same reference numerals denote the same functional members as those in the first embodiment.  
         [0051]     The structure of the CMOS solid state image sensor according to the second embodiment will be explained with reference to  FIG. 4 .  
         [0052]     Light incident on a solid state image sensor  100  is condensed by an on-chip microlens  25 . Light passes through a planarization layer  24 , color filter layer  23 , planarization layer  22 , protective layer  41 , interlayer dielectric film layer  21 , silicon nitride film layer  40 , and interlayer dielectric film layer  20 . Then, light is guided to a photo-electric converting portion  11  formed in a silicon substrate  10 .  
         [0053]     In  FIG. 4 , reference numeral  12  denotes a polysilicon electrode serving as a first electrode for transferring charges generated in the photo-electric converting portion  11 . Second and third electrodes  30  and  31  for selectively outputting transferred charges outside the solid state image sensor are respectively formed on the interlayer dielectric film layers  20  and  21 . The second and third electrodes  30  and  31  are generally formed from a metal such as aluminum. Reference numeral  60  denotes a via which connects the second and third electrodes  30  and  31 .  
         [0054]     In the solid state image sensor  100  according to the second embodiment, the silicon nitride film layer  40  covers the second electrode  30 . At an opening  30   a  of the second electrode  30 , a convex lens portion  40   a  is formed on the light incident side in a region where light condensed by the on-chip microlens  25  passes. Light condensed by the on-chip microlens  25  is deflected toward the photo-electric converting portion  11  by the convex lens portion  40   a  of the silicon nitride film layer  40 . Even light incoming at a large incident angle to the convex lens portion  40   a  can be efficiently guided to the photo-electric converting portion  11 . Since the convex lens portion  40   a  is convex on the light incident side, no total reflection of incident light occurs on the surface of the convex lens  40   a.    
         [0055]     A thickness t 1  of the convex lens portion  40   a  of the silicon nitride film layer  40  is set almost equal to a thickness ta of the second electrode  30 . The flatness is good, which facilitates planarization processing after the convex lens portion  40   a  of the silicon nitride film layer  40  is formed.  
         [0056]      FIGS. 5A  to  5 L and  6 M to  6 Q are sectional views for explaining a process of manufacturing the CMOS solid state image sensor  100  according to the second embodiment.  FIGS. 5A  to  5 L and  6 M to  6 Q illustrate the sectional structure of one pixel around the center of the frame of the solid state image sensor  100 .  
         [0057]     A silicon substrate  10  is thermally oxidized to form a silicon oxide film SiO (not shown) on the surface of the silicon substrate  10 . In order to form a photo-electric converting region in the silicon substrate  10 , a photoresist  50  is applied, exposed via a photomask of a predetermined pattern, and developed. For a positive photoresist, development processing dissolves the photoresist  50  in a region irradiated with light, i.e., a region  50   a  corresponding to the photo-electric converting region. As shown in  FIG. 5A , part of the silicon oxide film SiO is exposed. Ions are implanted into the silicon substrate  10  to form a photo-electric converting portion  11 .  
         [0058]     After the photo-electric converting portion  11  is formed in the silicon substrate  10 , the process advances to a step of forming, on the surface of the silicon substrate  10 , a first electrode  12  for transferring charges generated in the photo-electric converting portion  11 .  
         [0059]     A photoresist  51  is applied to the surface of the silicon substrate  10 , covered with a photomask (not shown), and exposed. The photomask is designed to transmit light in a region corresponding to the first electrode  12  which covers part of the photo-electric converting portion  11 , and shield light in the remaining region. By developing the photoresist  51 , the photoresist  51  in a region irradiated with light, i.e., a region  51   a  corresponding to the first electrode  12  dissolves. As shown in  FIG. 5B , part of the silicon oxide film SiO is exposed. As shown in  FIG. 5C , a polysilicon film  12   a  is formed, and the photoresist  51  is stripped to form the first electrode  12 .  
         [0060]     After the first electrode  12  is formed, a first interlayer dielectric film layer  20  for forming a second electrode  30  is formed and planarized, as shown in  FIG. 5D . The first interlayer dielectric film layer  20  is formed from a silicon oxide film SiO 2  at a refractive index of about 1.46.  
         [0061]     Then, the process advances to a step of forming a second electrode  30 .  
         [0062]     A photoresist  52  is applied, covered with a photomask corresponding to the pattern of the second electrode  30 , exposed, and developed. By developing the photoresist  52 , the photoresist  52  in a region irradiated with light, i.e., a region  52   a  corresponding to the second electrode  30  dissolves. As shown in  FIG. 5E , part of the first interlayer dielectric film layer  20  is exposed.  
         [0063]     Aluminum Al is deposited by a CVD apparatus or the like, and the photoresist  52  is stripped to form the second electrode  30 , as shown in  FIG. 5F .  
         [0064]     As shown in  FIG. 5G , a silicon nitride film layer  40  is formed to have a predetermined thickness to bury the opening  30   a  of the electrode  30 . Further, a convex lens portion  40   a  for increasing the condensing efficiency is formed in the opening region  30   a  of the electrode  30  where light condensed by the on-chip microlens  25  passes. For this purpose, a photoresist  53  is applied onto the silicon nitride film layer  40 , and planarized.  
         [0065]     As shown in  FIG. 5H , the photoresist  53  is covered with a photomask for forming a convex lens portion  53   a  and via region  53   b  in the photoresist  53 , exposed, and developed.  
         [0066]     After the predetermined convex lens shape  53   a  is formed in the photoresist  53  in a region corresponding to the opening  30   a  of the second electrode  30 , and the recess  53   b  is formed in the photoresist  53  in a region corresponding to the second electrode  30 , the convex lens shape  53   a  and recess  53   b  of the photoresist  53  are transferred to the silicon nitride film layer  40  by dry etching, as shown in  FIG. 5I . At this time, the vertex of the convex lens portion  40   a  formed in the silicon nitride film layer  40  is designed on the light incident side opposite to the surface of the second electrode  30 . A recess  40   b  formed in the silicon nitride film layer  40  exposes part of the electrode  30  covered with the silicon nitride film layer  40 .  
         [0067]      FIG. 7  is a plan view showing the solid state image sensor manufacturing step shown in  FIG. 5I .  
         [0068]     In  FIG. 7 , the second electrode  30  runs vertically, and the silicon nitride film layer  40  covers the second electrode  30 . At the opening  30   a  of the second electrode  30 , the convex lens portion  40   a  is formed in a region where light condensed by the on-chip microlens  25  passes. The second electrode  30  is exposed in the region  40   b  where a via is formed between the second and third electrodes  30  and  31 . As a result, the flatness improves because the silicon nitride film layer  40  is buried in a stepped region of the second electrode  30 .  
         [0069]     After the silicon nitride film layer  40  is buried in the opening  30   a  of the second electrode  30 , a second interlayer dielectric film layer  21  for forming a third electrode  31  is formed from a silicon oxide film SiO 2 , as shown in  FIG. 5J .  
         [0070]     After that, the process advances to a step of forming a via  60  for connecting the second and third electrodes  30  and  31 .  
         [0071]     A photoresist  54  is applied, covered with a photomask corresponding to the position of the via, exposed, and developed. By developing the photoresist  54 , the photoresist  54  in a region irradiated with light, i.e., a region  54   a  corresponding to the via  60  dissolves to expose part of the second interlayer dielectric film layer  21 . Dry etching is performed to form the via  60  in the second interlayer dielectric film layer  21 , as shown in  FIG. 5K . A metal plug  60   a  is buried in the via  60 , as shown in  FIG. 5L .  
         [0072]     The process advances to a step of forming a third electrode  31 .  
         [0073]     A photoresist  55  is applied, covered with a photomask corresponding to the pattern of the third electrode  31 , exposed, and developed. By developing the photoresist  55 , the photoresist  55  in a region irradiated with light, i.e., a region  55   a  corresponding to the third electrode  31  dissolves to expose part of the second interlayer dielectric film layer  21 , as shown in  FIG. 6M .  
         [0074]     Aluminum Al is deposited by the CVD apparatus or the like, and the photoresist  55  is stripped to form the third electrode  31 , as shown in  FIG. 6N .  
         [0075]     As shown in  FIG. 60 , a protective layer  41  is formed. The protective layer  41  is typically formed from a silicon oxynitride film.  
         [0076]     As shown in  FIG. 6P , a planarization layer  22  for forming a color filter layer is formed.  
         [0077]     Further, a color filter layer  23  is formed, and a planarization layer  24  for forming an on-chip microlens is formed on the color filter layer  23 . As shown in  FIG. 6Q , an on-chip microlens  25  is formed on the planarization layer  24 . The on-chip microlens  25  is formed by known resist reflow.  
         [0078]     In the second embodiment, the vertex of the convex lens portion  40   a  formed on the silicon nitride film layer  40  faces the light incident side opposite to the second electrode  30 . Alternatively, the vertex of the convex lens portion  40   a  formed on the silicon nitride film layer  40  may be located on almost the same plane as the surface of the second electrode  30 , as shown in  FIG. 8  which is a schematic side sectional view showing a CMOS solid state image sensor. This structure can shorten the interval between the second and third electrodes  30  and  31 .  
         [0079]     As described above, according to the embodiments, a plurality of metal electrode layers are interposed between the on-chip microlens and photo-electric converting portion of a solid state image sensor. On at least one surface having the metal electrode layers, a transparent film layer of high refractive index is formed to have a thickness almost equal to or larger than that of the metal electrode layer. In a region where light having passed through the on-chip microlens passes through the high-refractive-index film layer, the high-refractive-index film layer is formed into a convex lens shape which is convex on the light incident side. This structure can efficiently guide even light incoming at a large incident angle to the photo-electric converting portion while keeping short the distance between the on-chip microlens and the photo-electric converting portion.  
         [0080]     Since the lens portion of the high-refractive-index film layer has almost the same thickness as that of the metal electrode layer, planarization processing after formation of the convex lens portion can be facilitated.  
         [0081]     Since the high-refractive-index film layer covers the metal electrode layer, a process of newly forming a protective layer can be omitted.  
         [0082]     Moreover, an interconnection which connects the plurality of metal electrode layers is arranged, and the high-refractive-index film layer is formed in a region except the interconnection formation region. A convex lens can, therefore, be interposed between the metal electrode layers.  
         [0083]     According to the present invention, light incident on the microlens at a large incident angle can be efficiently guided to the photo-electric converting portion in the solid state image sensor.  
         [0084]     The present invention is not limited to the above embodiments and various changes and modifications can be made within the spirit and scope of the present invention. Therefore, to apprise the public of the scope of the present invention the following claims are made.  
         [0085]     This application claims the benefit of Japanese Patent Application No. 2005-011795 filed on Jan. 19, 2005, which is hereby incorporated by reference herein in its entirety.