Abstract:
Disclosed is an image sensor and method of fabricating the same. The image sensor includes a photoelectric transformation region formed in a semiconductor substrate, and pluralities of interlayer dielectric films formed over the photoelectric transformation regions. The interlayer dielectric films contain multilevel interconnection layers. A color filter layer is disposed in a well region formed in the interlayer dielectric films over the photoelectric transformation region. A passivation layer is interposed between the color filter layer and the interlayer dielectric films.

Description:
BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   Embodiments of the invention relate to image sensors. More particularly, embodiments of the invention relate to an image sensor having improved optical sensitivity and a related method of fabrication. 
   This application claims priority to Korean Patent Application 2005-06837filed on Jan. 25, 2005, the subject matter of which is hereby incorporated by reference. 
   2. Discussion of Background Art 
   Image sensors convert incident light into corresponding electrical signals (e.g., digital data) which may subsequently be used to form still or moving images. The term “incident light” generally refers to optical energy of any reasonable wavelength received by an image sensor. Conventional image sensors are basically composed of a pixel array. The pixel array is formed in turn by a uniform arrangement of photoelectric transformation regions, such as photodiodes. In order to detect, process, and output electrical signals having a color content, the conventional image sensor typically includes one or more color filter layers disposed on the pixel array. The color filter layers resolve the incident light (e.g., externally provided natural light) into various colored components, each having a specific wavelength (or range of wavelengths). 
   In one common implementation, the color filter layer is composed of various pluralities of color filters. Conventional color filters are generally classified into red-green-blue (RGB) color filters that resolve incident light into the primary colors; red (R), green (G), and blue (B), and complementary color filters that resolves incident light into the four colors of cyan (C), yellow (Y), green (G), and magenta (M). In a color filter layer comprising various pluralities of color filters, each color filter is adapted to communicate only a specific wavelength of light from the incident light to one or more corresponding photoelectric transformation region(s). 
   Figure (FIG.)  1 A is a plane view of a conventional image sensor principally illustrating a constituent pixel array.  FIG. 1B  is a related sectional view taken along with the line I-I′ of  FIG. 1A . 
   Referring to  FIGS. 1A and 1B , the pixel array of the conventional image sensor comprises a plurality of pixels arranged in two dimensions (e.g., an X/Y plane arrangement). Each pixel is defined by field isolation regions  12  formed in a semiconductor substrate  10 . Each pixel includes a photoelectric transformation region  14  formed in the semiconductor substrate  10  by which incident light is converted into electrical signals. Although not shown, each pixel also comprises conventionally understood connection circuits adapted to output the electrical signals resulting from the conversion of incident light by the photoelectric transformation region  14 . 
   A protection film  15  is formed on the resulting array of photoelectric transformation regions  14 . A stacked plurality of interlayer dielectric films  16  is then formed on protection layer  15 . Various pixel array interconnections,  18  and  18   t , associated with the foregoing connection circuits are generally formed in relation to interlayer dielectric films  16 . For example, interconnections  18  and  18   t  may be formed using multilevel interconnection techniques. In the illustrated example, the upper interconnection  18   t  may be formed with a lattice structure designed to selectively expose the photoelectric transformation region. That is, the upper interconnection may be designed to cover the peripheral portions (e.g., the edges) of the constituent photoelectric transformation regions to thereby function as a light shielding layer that protects the photoelectric transformation regions from exposure to undesired light beyond the intended incident light (e.g., incident light from a defined field of view). Such undesired light acts a noise signal to the intended incident light. 
   Color filter layers  20  are formed on an upper interlayer dielectric film  16 , and are respectively disposed over photoelectric transformation regions  14  of the pixel array. Within this configuration, each color filter  20  may optically select light at a specific wavelength from the incident light and communicate it to a corresponding photoelectric transformation region  14 . A protection film  22  is formed on color filter layers  20  to prevent damage to the color filter layers  20  during later stages of the manufacturing process. Microscopic lenses  24  are then disposed one for one over the respective color filter layers  20 . 
   In order to produce high-quality images, the effective optical sensitivity of the photoelectric transformation regions  14  to light incident must be improved. As illustrated in  FIGS. 1A and 1B , light communicated from color filter layers  20  must pass through a plurality of interlayer dielectric films  16  in the conventional image sensor in order to reach a photoelectric transformation region  14 . As the various interlayer dielectric films  16  contain materials having different refractive indexes, optical interference arises from a multiplicity of light signals variously refracted and reflected at, for example, surface interfaces between the individual interlayer dielectric films  16 . This optical interference causes a loss the effective throughput of the desired incident light. Further, since each interlayer dielectric film  16  has its own absorption coefficient, a decrease in the intensity of the incident light inevitably occurs along the optical path between the color filters  20  and the photoelectric transformation regions  14 . These two phenomenon are further exacerbated in the conventional image sensor by the effects of errant optical noise signals (e.g., stray incident light communicated through microscopic lenses  24  at some undesired refracted angle). Such errant optical noise signals may impact and reflect from multilevel interconnections  18  and  18   t  or otherwise abnormally progress through the vertical structure of the image sensor towards the photoelectric transformation regions. 
   SUMMARY OF THE INVENTION 
   Accordingly, embodiments of the invention are directed to an image sensor adapted to reduce the optical loss of incident light in relation to photoelectric transformation regions of the image sensor. Stated in positive terms, embodiments of the invention are directed to an image sensor adapted to increase the quantity (e.g., the intensity) of incident light received by photoelectric transformation regions of the image sensor. Embodiments of the invention are also directed to related methods of fabricating such an image sensor. 
   In one embodiment of the invention, an image sensor is provided with a reduced number of interlayer insulation films associated with color filter layers and photoelectric transformation regions. 
   Thus, in one embodiment, the invention provides an image sensor comprising; a photoelectric transformation region formed in a semiconductor substrate, a stacked interconnection element formed proximate to a peripheral portion of the photoelectric transformation region, the stacked interconnection element comprising a stacked plurality of interlayer dielectric films, wherein each interlayer dielectric layer comprises an interconnection layer, a color filter layer formed in relation to the stacked interconnection element on the photoelectric transformation region, a passivation layer interposed between the color filter layer and the stacked interconnection element, and a microscopic lens formed on the color filter layer. 
   In another embodiment, the invention provides an image sensor comprising; pixel array and peripheral circuit regions defined in a semiconductor substrate, a plurality of photoelectric transformation regions formed in the pixel array region, a first plurality of interlayer dielectric films formed over the peripheral circuit region, wherein each interlayer dielectric layer comprises an interconnection layer, wherein each one of the plurality of photoelectric transformation regions has associated therewith, a stacked interconnection element formed proximate to a peripheral portion of the photoelectric transformation region, wherein each stacked interconnection element is formed from a second plurality of the interlayer dielectric films less than the first plurality, a color filter layer formed in relation to the stacked interconnection element on the photoelectric transformation region, a passivation layer interposed between the color filter layer and the stacked interconnection element, and a microscopic lens formed on the color filter layer. 
   In yet another embodiment, the invention provides a method of fabricating an image sensor, comprising; forming a photoelectric transformation region in a semiconductor substrate, forming a stacked plurality of interlayer dielectric films on the photoelectric transformation region, wherein each one of the interlayer dielectric films comprises an interconnection layer and wherein one of the interconnection layers provided by the stacked plurality of interlayer dielectric films comprises a light shielding layer, patterning the stacked plurality of interlayer dielectric films to form a well region over the photoelectric transformation region in alignment with the light shielding layer, forming a passivation layer conformably over the well region, filling the well region with a color filter layer, and forming a microscopic lens on the color filter layer. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Several embodiments of the invention are described with reference to the accompanying drawings. In the drawings and corresponding portions of the specification, like numerals refer to like or similar elements. In the drawings, the thickness and relative size of various layers and regions may be exaggerated for clarity. In the drawings: 
       FIG. 1A  is a plane view of a conventional image sensor; 
       FIG. 1B  is a sectional view taken along with the line I-I′ of  FIG. 1A ; 
       FIG. 2  is a plane view illustrating an image sensor in accordance with a first embodiment of the invention; 
       FIG. 3A  is a sectional view taken along with the line II-II′ of  FIG. 2 ; 
       FIGS. 3B through 3E  are sectional views illustrating processing steps for fabricating the image sensor by the first embodiment of the invention; 
       FIGS. 4A through 4D  are sectional views illustrating an image sensor and processing steps for fabricating the same by a second embodiment of the invention; 
       FIGS. 5A through 5B  are sectional views illustrating an image sensor and processing steps for fabricating the same by a third embodiment of the invention; and, 
       FIGS. 6A through 6E  are sectional views illustrating an image sensor and processing steps for fabricating the same by a fourth embodiment of the invention. 
   

   DESCRIPTION OF EXEMPLARY EMBODIMENTS 
   Several embodiments of the invention will be described below in some additional detail with reference to the accompanying drawings. The present invention may, however, be embodied in different forms and should not be constructed as being limited to only the embodiments set forth herein. Rather, these embodiments are presented as teaching examples. It will also be understood from the following description that when a layer (or film), or element is referred to as being “on” another layer (or film), element, or substrate, it may be “directly on” the other layer (or film), element, or substrate, or intervening layers (or films) or elements may also be present. 
     FIG. 2  is a plane view illustrating an image sensor in accordance with a first embodiment of the invention.  FIG. 3A  is a related sectional view taken along with the line II-II′ of  FIG. 2 . 
   With reference to  FIGS. 2 and 3A , field isolation regions  52  are formed in a semiconductor substrate  50  to define pixel regions of a pixel array. Photoelectric transformation regions  54  are formed using conventional techniques and arranged within the pixel array. Photoelectric transformation regions  54  may be variously formed so long as they essentially provide conversion of incident light to electrical signals. However, in one embodiment, photoelectric transformation regions  54  are formed of photodiodes. Although not shown here for the sake of clarity, each pixel further comprises of a conventional local connection circuit adapted to provide the electrical signals generated from the incident light in response to a selection signal. 
   The exemplary pixel array further comprises multilevel interconnection layers  58  and  58   t . A number of interlayer dielectric films  56  are formed on substrate  50 , such that the multilevel interconnection layer,  58  and  58   t , are interposed between interlayer dielectric films  56 . 
   An upper multilevel interconnection layer  58   t  also functions as a light shielding layer. That is, light shielding layer  58   t  may be formed as a lattice structure on peripherals portions of the photoelectric transformation regions  54 , enabling effective communication of desired incident light to the photoelectric transformation regions  54 . One example of the latticed structure of light shielding layer  58   t  may be seen from the plane view of  FIG. 2 . As a matter of course, the light shielding layer  58   t  may serve a dual purpose as an interconnection layer adapted to transfer electrical signals from the photoelectric transformation regions  54 . 
   Color filter layers  64  are respectively formed on the photoelectric transformation regions  54 . In one embodiment, color filter layers  64  are constructed to in-fill a well region formed by sidewall portions of peripherally located (with respect to a photoelectric transformation regions  54 ) “stacked interconnection elements.” In the illustrated example, the stacked interconnection element is formed from an stack of interlayer dielectric layers  56  each comprising various interconnection layers, including interconnection layer(s)  58  and light shielding layers  58   t . Alternatively, the stacked interconnection elements may be formed from an alternating stack of interlayer dielectric films  56  and patterned metallization layers formed interconnection layers  58  and  58   t . In one embodiment, the lattice structure of light shielding layers  58   t  may be used to define the peripheral geometry of the stacked interconnection elements around the photoelectric transformation regions  54 . 
   Before formation of color filter layers  64 , however, a passivation film  62  may be conformably formed on the resulting structure of the stacked interconnection elements formed on substrate  50 . In particular, passivation film  62  covers the sidewall portions of the stacked interconnection elements, including the edge boundaries between contacting interlayer dielectric films  56  and multilevel interconnection layers  58  and  58   t , in order to prevent infiltration of impurities or moisture. Passivation film  62  may be formed to cover the entire well region in which color filter layers  64  are formed and may this constitute an optical waveguide structure. That is, passivation layer  62  will serve in some embodiments of the invention as an optical waveguide structure channeling incident light through a color filter layer  64  and preventing any lateral migration of incident light between adjacent pixels in the array, thereby reducing optical noise in the image sensor. This configuration also increases the amount of incident light reaching the photoelectric transformation regions  54  and greatly reduces the negative refractive effects associated with the multiple layer boundaries noted in the conventional image sensor configuration. 
   In one embodiment, passivation film  62  is formed from a material having a high refractive index relative to the color filter layers  64 , so as to induce the positive channeling (e.g., reflection) effects above, even in relation to optical signals having small incident angles at the boundary between color filter layers  64  and passivation film  62 . However, it should be noted that passivation film  62  is optional to embodiments of the invention, as even without passivation film  62 , the color filter layers  64  may be made from a material having a sufficiently low refractive index such that “total reflection” (e.g., the optical channeling effect) from the sidewalls of the stacked interconnection elements accomplished the desired results. 
   Also, a shield insulation film  55  may be provided between color filter layers  64  (or passivation film  62 ) and photoelectric transformation regions  54 . Shield insulation film  55  prevents damages to photoelectric transformation regions  54  during fabrication of the image sensor. Otherwise, damage to photoelectric transformation regions  54  may result on generation of dark currents and other noise signals. 
   Respective microscopic lens  70  may be arranged on each color filter layer  64 . Microscopic lenses  70  may be formed from a polyimide resin or a silicon oxide film, for example. In some embodiments, it may be beneficial to form a surface-flattening protection film  68  between microscopic lenses  70  and color filter layers  64 . In one embodiment the respective microscopic lenses  70  are formed with a planar surface area (e.g., the X/Y area shown in  FIG. 2 ) greater than the planar surface area of a corresponding color filter layer  64 . In other words, it is desirable for the border of the microscopic lenses  70  to be located over the light shielding layer  58   t  so as to effectively orient incident light through the microscopic lens  70  towards a corresponding photoelectric transformation region  54 . 
   An exemplary method adapted to fabricate the image sensor illustrated in  FIGS. 2 and 3A  will be described in some additional detail with respect to  FIGS. 3B through 3E  which are related sectional views. 
   First, referring to  FIG. 3B , field isolation regions  52  are formed in the semiconductor substrate  50 , thereby defining pixel regions in the pixel array of the image sensor. Respective photoelectric transformation regions  54  are then formed in each pixel region. Interlayer dielectric films  56  are then formed on substrate  50 . However, shield insulation film  55  may optionally be formed on substrate  50  following formation of photoelectric transformation regions  54 , but before formation of the first interlayer dielectric film  56 . In one embodiment, shield insulation film  55 , as formed from an appropriate material, may function as a first interlayer dielectric film. 
   In the illustrated example multilevel interconnection layers,  58  and  58   t , are formed within the interlayer dielectric films  56 . The stacked combination of interlayer dielectric films  56 , each comprising one or more multilevel interconnection layers (e.g.,  58  and  58   t ), serve to electrically connect photoelectric transformation regions  54  to local circuits in a conventionally understood manner. 
   An upper multilevel interconnection layer, (e.g., element  58   t ), may function as the light shielding layer. Light shielding layers  58   t  may be constructed in the form of a lattice being arranged on the peripheral portions of the photoelectric transformation regions  54 . 
   Referring to  FIG. 3C , the stacked plurality of interlayer dielectric films  56  are selectively patterned to form respective well regions  60  over a corresponding photoelectric transformation region  54 . Shield insulation film  55  may be used as an etch stop down to photoelectric transformation regions  54 , thus preventing damage to photoelectric transformation regions  54 . Well regions  60  may be formed in one embodiment by etching the interlayer dielectric films  56  using a self-alignment technique using light shielding layers  58   t  as a etch mask. Alternatively, the interlayer dielectric films  56  may be selectively etched using one or more patterned photoresist films formed in relation to light shielding layers  58   t  or in relation to some defined portion of the respective pixel regions. 
   In an embodiment where selective etching of interlayer dielectric films  56  is accomplished using either one or more photoresist films formed in relation to light shielding layer  58   t , or light shielding layer  58   t  itself, well regions  60  may be formed using self-aligned techniques such that the outer sidewall portions of well regions  60  are aligned with sidewalls of the light shielding layers  58   t . Thus, the pattern of light shielding layers  58   t  may be utilized as the etch mask even in circumstances where some degree of misalignment occurs between a formed photoresist film and light shielding layers  58   t . Further, well regions  60  may be formed to precisely expose a desired portion of each pixel region through the stacked interlayer dielectric films  56 . As a result, well regions  60  are aligned within openings defined by the lattice structure of light shielding layers  58   t , are accurately settled over the photoelectric transformation regions  54 . In one embodiment, the selective formation of well regions  60  defines the stacked interconnection structures around the peripheral portions of each pixel. 
   Referring to  FIG. 3D , passivation film  62  is conformably formed over the resulting structure on substrate  50 , and within well regions  60 . In particular, passivation film  62  is deposited on the inner walls of well regions  60  thereby covering the interconnection boundaries between interlayer dielectric films  56  and multilevel interconnection layers  58  and  58   t . In one embodiment, passivation film  62  is formed from a material having a relatively low light absorption coefficient and a relatively low refractive index relative to color filter layers  64  to be formed in well regions  60 . 
   Referring to  FIG. 3E , well regions  60  are filled with color filter layers  64 , each adapted to selectively communicate light having a specific wavelength. In one embodiment, color filter layers  64  are formed from a material having a refractive index higher than that of passivation film  62  so as to produce a total reflection channeling effect within color filter layer  64  between surfaces formed by passivation film  62 . However, even without passivation film  62 , color filter layers  64  may be formed from a material having a relatively higher refractive index than that of interlayer dielectric films  56 , so as to provide the foregoing optical channeling effect. 
   Subsequent to the formation of color filter layers  64 , the conventional microscopic lenses  70 , as shown in  FIG. 3A , may be formed in relation to the color filter layers  64 . Surface-flattening protection film  68  may be further deposited on the color filter layers  64  before forming the microscopic lenses  64 . 
   It should be noted at this point that different wavelengths have different optical responses to different materials. Thus, for any given choice of material used to form color filter layers  64 , light having a wavelength associated with the color red will have a different optical response (e.g., penetration ability and optical absorption) than light having a wavelength associated with the color blue. Thus, the thickness with which color filter layers  64 , as defined by the formation depth of corresponding well regions  60  may significantly impact the optical sensitivity of a particular, corresponding photoelectric transformation region  54 . An additional embodiment of the invention will now be described the addresses this recognition. 
     FIGS. 4A through 4D  are related sectional views illustrating a method adapted to the formation of an image sensor according to another embodiment of the invention. 
   Referring to  FIG. 4A , respective well regions  60   a ,  60   b , and  60   c  are formed to different depths. For example, if we assume that three (3) interlayer dielectric layers  56  are first formed on substrate  50 , first well region  60   a  is formed by selectively etching all three interlayer dielectric layers  56 , second well region  60   b  is formed by selectively etching the upper two interlayer dielectric layers  56 , and third well region  60   c  is formed by selectively etching only the uppermost interlayer dielectric layer  56 . However, even in this case, shield insulation film  55  may be provided to protect photoelectric transformation regions  54 . 
   Thereafter, referring to  FIG. 4B , passivation film  62   a  is conformably deposited over the resulting structure on substrate  50 , including well regions  60   a ,  60   b , and  60   c.    
   Referring to  FIG. 4C , respective color filter layers,  64   a ,  64   b , and  64   c , are then formed to fill well regions  60   a ,  60   b , and  60   c . The deeper well regions and correspondingly thicker color filters are provided in relation to colors (e.g., blue) that have a relatively weak transmission ability. In contrast, the shallower well regions and correspondingly thinner color filters are provided in relation to colors (e.g., red) that have a relatively strong transmission ability. That is, an increasing thickness of absorbent dielectric material is left between the mircolens and photoelectric transformation region in stronger color pixels. 
   Referring to  FIG. 4D , color filter layers  64   a ,  64   b , and  64   c  are added as is (optionally) surface-flattening protection film  68  and the microscopic lenses  70 . 
     FIGS. 5A through 5B  are sectional views illustrating an image sensor and a related method of fabrication according to another embodiment of the invention. 
   In general, microscopic lenses  70  within the foregoing image sensor embodiments may be conventionally formed by patterning and reflowing a polyimide resin or a low-temperature oxide (LTO) film. However, the following additional embodiment of the invention proposes another method of forming microscopic lenses  70 . 
   Referring to  FIG. 5A , after forming color filter layers  64  (or  64   a ,  64   b , and  64   c ) having been formed in the foregoing exemplary embodiments, a surface-flattening protection film  68   a  is formed on the respective resulting structures including the color filter layers. Protection film  68   a  may be formed from a material having superior physical properties than polyimide resin or LTO, (e.g., a material having a high transmittance, a low dispersion effect, and high resistance to environmental stress, etc.). Thereafter, microscopic lenses  70   a  may be formed on protection film  68   a  using conventional methods. 
   Referring to  FIG. 5B , microscopic lenses  70   a  and the protection film  68   a are anisotropically etched. As a result, the curvature of microscopic lenses  70   a  is transcribed onto protection film  68   a , thereby completing forming a final microscopic lense structure,  70   b , from protection film  68   a . In the illustrated embodiment of  FIG. 5B , protection film  68   a  is etched until the bordering edges of microscopic lense  70   b  contact with passivation film  62 . However, microscopic lenses of any reasonable thickness may be formed from protection film  68   b.    
     FIGS. 6A through 6E  are sectional views illustrating an image sensor and a related method of fabrication according to another embodiment of the invention. This embodiment may be useful for improving the optical sensitivity when a low-transmittance material layer is formed over the photoelectric transformation regions. 
   Referring to  FIG. 6A , field isolation regions  102  are formed to define pixel regions within a pixel array region (CE) and peripheral circuit (PE) regions in a semiconductor substrate  100 . Thereafter photoelectric transformation regions  104 , such as photodiodes, are formed in the individual pixel regions. A number (a first plurality) of interlayer dielectric films  106  are then formed on semiconductor substrate  100 , each interlayer dielectric layer  106  comprising one or more interconnection layers, (e.g.,  108  and  108   p ). 
   Interconnection layers  108  in the pixel array field may, for example, be connected to transistors arranged in the pixel array (CE) region, while interconnection layers  108   p  may be connected to interconnection layers  108  or transistors arranged in the peripheral circuit region (PE). While the pixel array region comprises circuits adapted to select individual pixels, the peripheral circuit region comprises circuits adapted to generally drive the image sensor including the pixel array. Thus, the peripheral circuit region is typically constructed with a greater number of interconnection layers than are found in the pixel array region. As before noted, the uppermost interconnection layers, (e.g.,  108   t ), may be used as a light shielding layer. 
   The multilevel interconnection layers  108  and  108   p  may be formed using a conventionally understood damascene process. Etch-stop layers  107  may be interposed between adjacent interlayer dielectric films  106  in order to protect lower interlevel interconnection films while patterning interlayer dielectric films  106  to form the multilevel interconnection layers  108 . The etch-stop layers  107  may be formed from silicon oxide as generally used in conjunction with silicon nitride films. The silicon nitride film has a lower transmittance than the silicon oxide film. If the etch-stop layers  107  are interposed between adjacent interlayer dielectric films  106  for the multilevel interconnection layers  108 , the intensity of light transmitting the interlayer dielectric films  106  and the etch-stop layers  107  is weakened, which may cause a reduction in the optical sensitivity of the image sensor. 
   Next, referring to  FIG. 6B , the first plurality of interlayer dielectric films  106  and the etch-stop layers  107  are removed in the pixel array region over the light shielding layers  108   t  to define a second plurality of interlayer dielectric films. As a result, a cavity  109  is formed in the pixel array region, being lower than the peripheral circuit region, which is helpful for reducing the thickness of the insulation film that covers the photoelectric transformation regions  104 . Although not shown, a processing step of forming cavity  109  may be carried out after the formation of related bonding pads in the peripheral circuit region. 
   Referring to  FIG. 6C , well regions  110  are then formed by selectively removing portions of the second plurality of interlayer dielectric films  106  and etch-stopping layers  107  in the pixel array region being aligned to light shielding layers  108   t . As aforementioned through the former embodiments, light shielding layers  108   t  may be formed in a lattice structure defining well region openings. Thus, interlayer dielectric films  106  and etch-stopping layers  107  may be selectively removed using light shielding layers  108   t  as an etch mask, or by using a photoresist pattern defined in relation to light shielding layers  108   t . Using either technique, peripheral circuit region may be effectively protected. Before forming interlayer dielectric films  106 , a shield insulation film  105  may be further deposited to protect the photoelectric transformation regions  104 . It is preferable in one embodiment that well regions  110  be formed such that shield insulation film  105  remains on the photoelectric transformation regions  104 , thereby preventing the photoelectric transformation regions  104  from being damaged. 
   Thereafter, referring to  FIG. 6D , color filter layers  114  are respectively formed within well regions  110 . As with the former embodiment(s), well regions  110  may be formed with various depths in accordance with different kinds of color filter layers. And, a passivation layer may be conformably deposited over the substrate  100  including well regions  110 , before forming the color filter layers  114 . Passivation layer  112  is adapted to effect an optical waveguide structure surrounding sidewall portions of color filter layers  112 . As above, passivation layer  112  may be formed from a material having a relatively lower refractive index than the color filter layers  114 , so that the light communicated by the color filter layer is channeled as described above. 
   Referring to  FIG. 6E , a surface-flattening protection film  118  is deposited over the pixel array region including color filter layers  114  and then microscopic lenses  120  are each formed rightly over color filter layers  114 . Microscopic lenses  120  may be formed as described above. 
   According to this illustrative embodiment of the invention, cavity  109  over pixel array region is helpful in decreasing the number of the insulation layers stacked on the photoelectric transformation regions  104 , and therefore eliminating low-transmittance insulation layers. Therefore, it is possible to raise the optical sensitivity of the image sensor, which becomes more effective owing to the structure that sidewalls of color filter layers  114  as aligned with sidewalls of light shielding layer  108   t  in the pixel array region. 
   According to the invention as variously described above, it is able to remarkably reduce the number of material layers (and associated intervening material) over photoelectric transformation regions to reduce optical loss of the desired incident light. Improve wavelength selectivity may also be accomplished by substituting the interlayer dielectric films with the color filter layers selectively transmitting specific wavelengths. Further, an optical waveguide function may be provided in relation to the color filter layers using a passivation layer, thereby further reducing the optical losses of incident light communicated through the color filter layers. 
   In addition, as the curvature of the microscopic lens pattern is transcribed to the lower film after forming the microscopic lens pattern, it is possible to complete the microscopic lenses of material with a high transmittance and endurance against external environments. 
   While the present invention has been described in connection with the embodiments of the invention illustrated in the accompanying drawings, it is not limited thereto. It will be apparent to those skilled in the art that various substitution, modifications and changes may be thereto without departing from the scope and of the invention as defined by the following claims.