Abstract:
A method of forming a piezoelectric resonant device having a piezoelectric resonator is provided. The method offers a plan for increasing the electrical characteristics of the piezoelectric resonator by ensuring a green substrate having a desired thickness from a green body. According to the method, two green bodies are prepared. Green substrates are formed by sequentially performing sintering and grinding processes on the green bodies. Internal and external substrate electrode patterns are formed on facing surfaces between the green substrates and opposite surfaces to the facing surfaces. An adhesive agent is formed on the facing surfaces between the green substrates. A piezoelectric resonant pattern is formed by cutting the green substrates. A piezoelectric resonator is formed by disposing respective connection electrodes on both sides of the piezoelectric resonant pattern.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
       [0001]    This application claims the benefit of Korean Patent Application No. 10-2006-0137471, filed Dec. 29, 2006, the disclosure of which is hereby incorporated herein by reference in its entirety. 
       BACKGROUND OF THE INVENTION 
       [0002]    1. Field of the Invention 
         [0003]    The present invention relates to methods of forming a piezoelectric resonant device, and more particularly, to methods of forming a piezoelectric resonant device having a piezoelectric resonator. 
         [0004]    2. Description of the Related Art 
         [0005]    In general, piezoelectric resonant devices are electronic discrete devices which are able to obtain acoustic waves with a target frequency from electromagnetic waves with several frequencies using a piezoelectric resonator. Here, the piezoelectric resonator may be formed through pre- and post-processing steps. The pre-processing step includes forming inner substrate electrode patterns on surfaces facing each other between green bodies, and forming green substrates by performing sintering and grinding processes on the green bodies. The green bodies may be formed of a piezoelectric material. And, the post-processing step includes forming external substrate electrode patterns on surfaces facing each other between the green substrates, and cutting the green substrates. A thickness of each green substrate can provide acoustic waves with a target frequency to the piezoelectric resonator. 
         [0006]    However, the piezoelectric resonator may not show the acoustic waves with a target frequency to a piezoelectric resonant device because the piezoelectric resonator is formed through the processing steps of sintering and grinding the green bodies. That is, the green bodies have internal substrate electrode patterns between them before the sintering process. Also, the green bodies are sintered to have a different thermal expansion coefficient from the inner substrate electrode patterns during the sintering process. Thus, after the sintering process, the green bodies may have different thicknesses at parts in contact with the inner substrate electrode patterns and near the inner substrate electrode patterns. Also, each green body may have a different thickness at an upper part and a lower part between which the inner substrate electrode pattern is interposed due to an effect of gravity according to a physical phenomenon by the grinding process. 
         [0007]    A method of forming the piezoelectric resonator is disclosed by Takeshima Tetsuo in Korean Patent No. 10-0307679. According to Korean Patent No. 10-0307679, several green sheets (green bodies) are prepared and conductive pastes are formed on the respective green sheets. A multilayered base is formed by stacking and plasticizing the green sheets. Here, the conductive pastes are formed of inner electrodes after the plasticizing process, respectively. Polarized electrodes are formed on selected both sides of the multilayered base, respectively. The multilayered base is polarized by the polarized electrodes, a multilayered body is formed by cutting the multilayered base, insulating layers and external electrodes are formed on the multilayered body, and the external electrodes, the insulating layers and the multilayered body are cut to form a piezoelectric resonator. 
         [0008]    However, this method of forming the piezoelectric resonator includes interposing conductive pastes between green sheets and forming inner electrodes by a plasticizing process. Here, the green sheets may have different thicknesses at a part in contact with the conductive pastes and near the conductive pastes through the plasticizing process. Also, this method of forming the piezoelectric resonator may raise production cost due to complicated formation steps. 
       SUMMARY OF THE INVENTION 
       [0009]    An embodiment of the invention provides methods of forming a piezoelectric resonant device capable of minimizing an effect of a production process on green bodies in order to improve an electrical characteristic of a piezoelectric resonator. 
         [0010]    In one aspect, the invention is directed to methods of forming a piezoelectric resonant device having a piezoelectric resonator. 
         [0011]    In a first embodiment, the method comprises preparing two green bodies, each green body being sintered and formed into a cube surrounded by six planes. Green substrates are formed by grinding each green body, respectively. Substrate polarizing layers are formed on facing surfaces between the green substrates, and on opposite surfaces to the facing surfaces, respectively. The green substrates are polarized using the substrate polarizing layers. Also, internal and external substrate electrode patterns are formed on the green substrates using the substrate polarizing layers. The internal and external substrate electrode patterns are formed on the facing surfaces between the green substrates, and the opposite surfaces to the facing surfaces, respectively, and an adhesive agent is formed on the facing surfaces between the green substrates. At least one piezoelectric resonant pattern is formed by cutting the green substrates, and the piezoelectric resonant pattern has a connecting adhesive pattern, an insulating adhesive pattern, resonant patterns, and external and internal resonant electrode patterns. The external and internal resonant electrode patterns and the resonant patterns correspond to the external and internal substrate electrode patterns and the green substrates, respectively. The connecting and insulating adhesive patterns correspond to the adhesive agent. A piezoelectric resonator having connection electrodes between the internal resonant electrode patterns and between the external resonant electrode patterns to be disposed on the piezoelectric resonant pattern is formed. 
         [0012]    In a second embodiment, the method comprises preparing two or more even number of green bodies. Each green body is sintered and formed into a cube surrounded by six planes. Green substrates are formed by grinding the green bodies, and substrate polarizing layers are formed on facing surfaces between the green substrates and opposite surfaces to the facing surfaces. The green substrates are polarized using the substrate polarizing layers. Two substrates are selected from the green substrates to thereby form internal and external substrate electrode patterns thereon. The internal and external substrate electrode patterns are formed on the facing surfaces between the green substrates and the opposite surfaces to the facing surfaces using the substrate polarizing layer, respectively. An adhesive agent is formed on the facing surfaces between the two green substrates, and at least one piezoelectric resonant pattern is formed by cutting the two green substrates. The piezoelectric resonant pattern has a connecting adhesive pattern, an insulating adhesive pattern, resonant patterns, external resonant electrode patterns, and internal resonant electrode patterns. The external and internal resonant electrode patterns and the resonant patterns correspond to the external and internal substrate electrode patterns and the green substrates, respectively. The connecting and insulating adhesive patterns correspond to the adhesive agent. A piezoelectric resonator having connection electrodes between the internal resonant electrode patterns and between the external resonant electrode patterns to be disposed on the piezoelectric resonant pattern is formed. Two from the rest of the green substrates are repeatedly selected in a unit to sequentially form the internal and external substrate electrode patterns thereon, the adhesive agent, the piezoelectric resonant pattern, and the piezoelectric resonator. 
         [0013]    In a third embodiment, two or more even number of green bodies are prepared. Each green body is sintered and formed into a cube surrounded by six planes. Green substrates are formed by grinding the green bodies, respectively, and substrate polarizing layers are formed on facing surfaces between the green substrates and opposite surfaces to the facing surfaces. The green substrates are polarized using the substrate polarizing layers, and two green substrates are selected from the green substrates to form internal and external substrate electrode patterns thereon. The internal and external substrate electrode patterns are formed on the facing surfaces between the two green substrates and the opposite surfaces to the facing surfaces using the substrate polarizing layers. An adhesive agent is formed on the facing surfaces between the two green substrates. Two from the rest of the green substrates are repeatedly selected in a unit to sequentially form the internal and external substrate electrode patterns thereon, and the adhesive agent. Piezoelectric resonant patterns are formed by cutting the green substrates, each of the piezoelectric resonant patterns having a connecting adhesive pattern, an insulating adhesive pattern, resonant patterns, external resonant electrode patterns, and internal resonant electrode patterns. The external and internal resonant electrode patterns and the resonant patterns correspond to the external and internal substrate electrode patterns and the green substrates, respectively. The connecting and insulating adhesive patterns correspond to the adhesive agent. One from the piezoelectric resonant patterns is repeatedly selected in a unit, thereby forming a plurality of piezoelectric resonators having connection electrodes between the internal resonant electrode patterns and also between the external resonant electrode patterns to be disposed on the piezoelectric resonant pattern. 
         [0014]    In a fourth embodiment, two green bodies are prepared. Each green body is sintered and formed into a cube surrounded by six planes. Green substrates are formed by grinding the green bodies, respectively. Internal and external substrate electrode patterns are formed on facing surfaces between the green substrates, and on opposite surfaces to the facing surfaces, respectively. The green substrates are polarized using the internal and external substrate electrode patterns, and an adhesive agent is formed on the facing surfaces between the green substrates. At least one piezoelectric resonant pattern is formed by cutting the green substrates, the least one piezoelectric resonant pattern having a connecting adhesive pattern, an insulating adhesive pattern, resonant patterns, external resonant electrode patterns, and internal resonant electrode patterns. The external and internal resonant electrode patterns and the resonant patterns correspond to the external and internal substrate electrode patterns and the green substrates, respectively. The connecting and insulating adhesive patterns correspond to the adhesive agent. A piezoelectric resonator having connection electrodes between the internal resonant electrode patterns and between the external resonant electrode patterns to be disposed on the piezoelectric resonant pattern, is formed. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0015]    The foregoing and other objects, features and advantages of the invention will become more apparent from the following more particular description of exemplary embodiments of the invention and the accompanying drawings. The drawings are not necessarily to scale, emphasis instead being placed upon illustrating the principles of the invention. 
           [0016]      FIGS. 1 to 7  are perspective views illustrating a method of forming a piezoelectric resonant device having a piezoelectric resonator according to the present invention. 
           [0017]      FIGS. 8  is a cross-sectional view of a multilayered piezoelectric resonant device having the piezoelectric resonator of  FIG. 7 . 
           [0018]      FIG. 9  is a cross-sectional view of a cap-shaped piezoelectric resonant device having the piezoelectric resonator of  FIG. 7 . 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0019]    The present invention will now be described more fully hereinafter with reference to the accompanying drawings, in which exemplary embodiments of the invention are shown. 
         [0020]      FIGS. 1 to 7  are perspective views illustrating a method of forming a piezoelectric resonant device having a piezoelectric resonator according to the present invention. 
         [0021]    Referring to  FIG. 1 , two green bodies  2  and  4  are prepared. The green bodies may be ensured by a green compact (not illustrated). That is, the green bodies  2  and  4  may be formed by pressing, casting or extruding the green compact, techniques which are well known to those skilled in the art. Each of the green bodies  2  and  4  may be formed to be surrounded by six planes. Alternatively, the green bodies  2  and  4  may be prepared in two or more even number and the green compact may be formed of a piezoelectric material. Here, the green compact may be formed of several crystals. 
         [0022]    Referring to  FIGS. 1 and 2 , a sintering process using a predetermined temperature is performed to harden the green bodies  2  and  4 . The predetermined temperature in the sintering process may have an appropriate value in a range of temperatures well known to those in the art to harden the green bodies  2  and  4 , or to improve an electrical characteristic of a piezoelectric resonator  70  of  FIG. 7 . Subsequently, after the sintering process, a grinding process is performed on the green bodies  2  and  4 , thereby forming green substrates  6  and  8  as illustrated in  FIG. 2 . 
         [0023]    Meanwhile, when two green bodies  2  and  4  are prepared, forming the green substrates  6  and  8  may comprise: two-dimensionally arranging the green bodies  2  and  4  in a grinding apparatus according to first and fourth embodiments of the present invention; and simultaneously performing the grinding process onto the green substrates  2  and  4 . Alternatively, forming the green substrates  6  and  8  may comprise: inserting one of the green bodies  2  and  4  into the grinding apparatus according to the first and fourth embodiments of the present invention; performing the grinding process on the selected one; and inserting the other green body into the grinding apparatus to grind. As a result, the green substrates  2  and  4  may be formed to have the same thickness through the grinding process. 
         [0024]    When two or more even number of green bodies are prepared, according to second and third embodiments of the present invention, forming green substrates comprises: two-dimensionally arranging the green bodies in the grinding apparatus; and simultaneously performing the grinding process to the green bodies. Alternatively, forming the green substrates may comprise: inserting one of the green bodies into the grinding apparatus; performing the grinding process on the selected one; and subsequently repeatedly selecting one from the rest of the green bodies, inserting the selected one into the grinding apparatus, and performing the grinding process. As a result, the green substrates may be formed to the same thickness through the grinding process. 
         [0025]    Referring to  FIGS. 2 and 3 , substrate polarizing layers  12  and  14  are formed on the green substrates  6  and  8  as illustrated in  FIG. 3 . The substrate polarizing layers  12  and  14  may be formed of a conductive material including silver (Ag), and each substrate polarizing layer  12  or  14  may be formed of at least one conductive layer. When two green bodies  12  and  14  are prepared, the green substrates  6  and  8  are polarized by the substrate polarizing layers  12  and  14  according to the first embodiment of the present invention. Here, polarizing the green substrates  6  and  8  comprises directly contacting electrical wires to the substrate polarizing layers  12  and  14  and aligning polarized axes of the crystals in the green substrates  6  and  8  in the same direction. Alternatively, polarizing the green substrates  6  and  8  may comprise forming an electric field around the substrate polarizing layers  12  and  14 , and aligning the polarized axes of the crystals in the green substrates  6  and  8  parallel to each other. 
         [0026]    Meanwhile, when two or more even number of green bodies are prepared, the green substrates are polarized using the substrate polarizing layers according to the second and third embodiments of the present invention. Here, polarizing the green substrates comprises directly contacting electrical wires to the substrate polarizing layers to align the polarized exes of the crystals in the green substrates parallel to each other. Alternatively, polarizing the green substrates may comprise forming an electric field around the substrate polarizing layers to align the polarized axes of the crystals in the green substrates parallel to each other. Accordingly, the substrate polarizing layers of the second and third embodiments of the present invention may be formed of the same material as the substrate polarizing layers  12  and  14  of the first embodiment of the present invention. The substrate polarizing layers of the second and third embodiments of the present invention may be formed of at least one conductive layer. Unlike the first and third embodiments of the present invention, the fourth embodiment does not have the substrate polarizing layers  12  and  14  on the green substrates  6  and  8 . 
         [0027]    Referring to  FIGS. 3 and 4 , internal and external substrate electrode patterns  16  and  18  are formed on the green substrates  6  and  8  according to the first embodiment of the present invention as illustrated in  FIG. 4 . The internal and external substrate electrode patterns  16  and  18  may be formed on the facing surfaces between the green substrates  6  and  8 , and the opposite surfaces to the facing surfaces, respectively. Here, when two green bodies  2  and  4  are prepared, forming the internal and external substrate electrode patterns  16  and  18  comprises: forming photoresist patterns on the substrate polarizing layers  12  and  14 ; removing the substrate polarizing layers  12  and  14  using the photoresist patterns and the green substrates  6  and  8  as an etch mask and an etch buffer layer, respectively; and removing the photoresist patterns from the green substrates  6  and  8 . Here, the photoresist patterns may be formed to correspond to the internal substrate electrode patterns  16 , respectively. 
         [0028]    Subsequently, forming the internal and external substrate electrode patterns  16  and  18  further comprises: forming other photoresist patterns on the substrate polarizing layers  12  and  14 ; removing the substrate polarizing layers  12  and  14  using the other photoresist layers and the green substrates  6  and  8  as an etch mask and an etch buffer layer; and removing the other photoresist patterns from the green substrates  6  and  8 . Here, the other photoresist patterns may be formed to correspond to the external substrate electrode patterns  18 , respectively. As a result, the internal substrate electrode patterns  16  may be disposed between the external substrate electrode patterns  18  to overlap each other. Alternatively, the external substrate electrode patterns  18  may be formed to be disposed between the internal substrate electrode patterns  16 . 
         [0029]    Referring again to  FIGS. 3 and 4 , when two or more even number of green bodies are prepared, two substrates are selected from the green substrates, and the internal and external substrate electrode patterns  16  and  18  are formed thereon in the same way as the first embodiment of the present invention according to the second and third embodiments of the present invention. Thus, the internal and external substrate electrode patterns  16  and  18  may be formed on the facing surfaces between the two green substrates  6  and  8  and the opposite surfaces to the facing surfaces using the substrate polarizing layers  12  and  14 , respectively. 
         [0030]    Meanwhile, forming the internal and external substrate electrode patterns  16  and  18  comprises: forming photoresist patterns on the substrate polarizing layers  12  and  14 ; removing the substrate polarizing layers  12  and  14  using the photoresist patterns and the two green substrates  6  and  8  as an etch mask and an etch buffer layer, respectively; and removing the photoresist patterns from the two green substrates  6  and  8 . Here, the photoresist patterns may be formed to correspond to the internal substrate electrode patterns  16 , respectively. 
         [0031]    Subsequently, forming the internal and external substrate electrode patterns  16  and  18  further comprises: forming other photoresist patterns on the substrate polarizing layers  12  and  14 ; removing the substrate polarizing layers  12  and  14  using the other photoresist patterns and the two green substrate  6  and  8  as an etch mask and an etch buffer layer; and removing the other photoresist patterns from the two green substrates  6  and  8 . Here, the other photoresist patterns may be formed to correspond to the external substrate electrode patterns  18 , respectively. Therefore, the internal substrate electrode patterns  16  may be disposed between the external substrate electrode patterns  18  to overlap each other. Alternatively, the external substrate electrode patterns  18  may be formed to be disposed between the internal substrate electrode patterns  16 . 
         [0032]    Referring again to  FIGS. 3 and 4 , unlike the first to third embodiment of the present invention, when two green bodies  2  and  4  are prepared, the internal and external substrate electrode patterns  16  and  18  are formed on the facing surfaces between the green substrates  6  and  8  and the opposite surfaces to the facing surfaces, respectively, according to the fourth embodiment of the present invention. Here, forming the internal and external substrate electrode patterns  16  and  18  comprises forming conductive paste patterns on the green substrates  6  and  8 , and forming other conductive paste patterns on the green substrates  6  and  8 . Also, forming the internal and external substrate electrode patterns  16  and  18  further comprises thermally treating the green substrates  6  and  8 , the conductive paste patterns and the other conductive paste patterns. The conductive pastes and the other conductive pastes may be formed of a conductive material, including Ag. 
         [0033]    Meanwhile, the conductive paste patterns may be formed to correspond to the internal substrate electrode patterns  16 , respectively. The other conductive paste patterns may be formed to correspond to the external substrate electrode patterns  18 , respectively. Also, the internal substrate electrode patterns  16  may be disposed between the external substrate electrode patterns  18  to overlap each other. Alternatively, the external substrate electrode patterns  18  may be formed to be disposed between the internal substrate electrode patterns  16 . Subsequently, the green substrates  6  and  8  are polarized using the internal and external substrate electrode patterns  16  and  18  according to the fourth embodiment of the present invention. Here, polarizing the green substrates  6  and  8  comprises directly contacting electrical wires to the internal and external substrate electrode patterns  16  and  18  to align polarized axes of crystals parallel to each other in the green substrates  6  and  8 . Alternatively, polarizing the green substrates  6  and  8  may comprise forming an electric field around the internal and external substrate electrode patterns  16  and  18  to align the polarized axes of the crystals parallel to each other in the green substrates  6  and  8 . 
         [0034]    Referring to  FIGS. 4 and 5 , when two green bodies  2  and  4  are prepared, an adhesive agent  29  is formed on the facing surfaces between the green substrates  6  and  8  according to the first and fourth embodiments of the present invention as illustrated in  FIG. 5 . The adhesive agent  29  is formed of a connecting adhesive layer  24  and an insulating adhesive layer  28 . The insulating adhesive layer  28  may be formed of an insulating material and the connecting adhesive layer  24  may be formed of a conductive material. Here, the connecting adhesive layer  24  may be formed to be in contact with the internal substrate electrode patterns  16 , and the insulating adhesive layer  28  may be disposed between the internal substrate electrode patterns  16  to be in contact with the green substrates  6  and  8 . 
         [0035]    Alternatively, when two or more even number of green bodies are prepared, a pair of substrates from the green substrates are selected, and the adhesive agent  29  is formed on the facing surfaces between the two green substrates  6  and  8  according to the second and third embodiments of the present invention. The adhesive agent  29  is formed of the connecting adhesive layer  24  and the insulating adhesive layer  28 . Here, the connecting adhesive layer  24  may be in contact with the internal substrate electrode patterns  16 , and the insulating adhesive layer  28  may be disposed between the internal substrate electrode patterns  16  to be in contact with the green substrates  6  and  8 . 
         [0036]    Referring to  FIGS. 5 and 6 , when two green bodies  2  and  4  are prepared, at least one piezoelectric resonant pattern  70  is formed by cutting the green substrates  6  and  8  according to the first and fourth embodiments of the present invention as illustrated in  FIG. 6 . Cutting the green substrates  6  and  8  may be performed by a dicing saw technique. The piezoelectric resonant pattern  70  has external resonant electrode patterns  34  and  38 , resonant patterns  44  and  48 , internal resonant electrode patterns  54  and  58 , connecting adhesive pattern  64  and the insulating adhesive pattern  68 . The insulating adhesive pattern  68  may be disposed between the resonant patterns  44  and  48  to be in contact with the connecting adhesive pattern  64  and the external and internal resonant electrode patterns  34 ,  38 ,  54  and  58 . The insulating adhesive pattern  68  corresponds to the insulating adhesive layer  28 . The connecting adhesive pattern  64  may be formed to be disposed between the internal resonant electrode patterns  54  and  58 . The connecting adhesive pattern  64  corresponds to the connecting adhesive layer  24 . 
         [0037]    The internal resonant electrode patterns  54  and  58  may be formed to be disposed on one side of the facing surfaces between the resonant patterns  44  and  48  to face each other. The external resonant electrode patterns  34  and  38  may be formed on the opposite surfaces to the facing surfaces between the resonant patterns  44  and  48  to overlap the other side of the facing surfaces between the resonant patterns  44  and  48 . The external resonant electrode patterns  34  and  38  may or may not overlap the internal resonant electrode patterns  54  and  58 . The external and internal resonant electrode patterns  34 ,  38 ,  54  and  58  correspond to the internal and external substrate electrode patterns  16  and  18 , respectively. 
         [0038]    Forming the piezoelectric resonant pattern  70  comprises cutting the green substrates  6  and  8  along line B 1 -B 2  as sequentially passing between the internal and external substrate electrode patterns  16  and  18  along lines A 1 -A 2 , A 3 -A 4 , A 5 -A 6 , A 7 -A 8  and A 9 -A 10 , and crossing the internal and external substrate electrode patterns  16  and  18  as illustrated in  FIG. 5 . Alternatively, forming the piezoelectric resonant pattern  70  may comprise sequentially cutting the green substrates  6  and  8  along line B 1 -B 2  crossing the internal and external substrate electrode patterns  16  and  18 , and along lines A 1 -A 2 , A 3 -A 4 , A 5 -A 6 , A 7 -A 8  and A 9 -A 10  passing between the internal and external substrate electrode patterns  16  and  18 . 
         [0039]    Referring again to  FIGS. 5 and 6 , when two or more even number of green bodies are prepared, at least one piezoelectric resonant pattern  70  is formed by cutting two green substrates  6  and  8 , which are selected from the green substrates according to the second embodiment of the present invention. Cutting the two green substrates  6  and  8  may be performed by the dicing saw technique. The piezoelectric resonant pattern  70  has external resonant electrode patterns  34  and  38 , resonant patterns  44  and  48 , internal resonant electrode patterns  54  and  58 , a connecting adhesive pattern  64  and an insulating adhesive pattern  68 . The insulating adhesive pattern  68  (corresponding to the insulating adhesive layer  28 ) may be disposed between the resonant patterns  44  and  48  to be in contact with the connecting adhesive pattern  64 , and the external and internal resonant electrode patterns  34 ,  38 ,  54  and  58 . The connecting adhesive pattern  64  corresponding to the connecting adhesive layer  24  may be formed to be disposed between the internal resonant electrode patterns  54  and  58 . 
         [0040]    The internal resonant electrode patterns  54  and  58  may be disposed on one side respectively of the facing surfaces between the resonant patterns  44  and  48  to face each other. The external resonant electrode patterns  34  and  38  may be formed on the opposite surfaces to the facing surfaces between the resonant patterns  44  and  48  to overlap the other side of the facing surfaces between the resonant patterns  44  and  48 . The external resonant electrode patterns  34  and  38  may or may not overlap the internal resonant electrode patterns  54  and  58 . The external and internal resonant electrode patterns  34 ,  38 ,  54  and  58  correspond to the internal and external substrate electrode patterns  16  and  18 , respectively. 
         [0041]    Forming the piezoelectric resonant pattern  70  comprises sequentially cutting the green substrates  6  and  8 , as illustrated in  FIG. 5 , along lines A 1 -A 2 , A 3 -A 4 , A 5 -A 6 , A 7 -A 8 , and A 9 -A 10  passing between the internal and external substrate electrode patterns  16  and  18 , and along line B 1 -B 2  crossing the internal and external substrate electrode patterns  16  and  18 . Alternatively, forming the piezoelectric resonant pattern  70  may comprise sequentially cutting the green substrates  6  and  8  along line B 1 -B 2  crossing the internal and external substrate electrode patterns  16  and  18 , and along lines A 1 -A 2 , A 3 -A 4 , A 5 -A 6 , A 7 -A 8  and A 9 -A 10  passing between the internal and external substrate electrode patterns  16  and  18 . 
         [0042]    Referring again to  FIGS. 5 and 6 , when two or more even number of green bodies are prepared, according to the third embodiment of the present invention, a pair of substrates are selected from the rest of the green substrates so as to form the internal and external substrate electrode patterns, and the adhesive agent is formed, sequentially. Thus, the third embodiment of the present invention may provide several pairs of green substrates. Subsequently, piezoelectric resonant patterns are formed by cutting the green substrates. Cutting the green substrates may be performed by the dicing saw technique. 
         [0043]    Each piezoelectric resonant pattern has the same structure as the piezoelectric resonant pattern  70  of  FIG. 6 . Thus, each piezoelectric resonant pattern has external resonant electrode patterns  34  and  38 , resonant patterns  44  and  48 , internal resonant electrode patterns  54  and  58 , a connecting adhesive pattern  64  and an insulating adhesive pattern  68 . The insulating adhesive pattern  68  (corresponding to the insulating adhesive layer  28 ) may be disposed between the resonant patterns  44  and  48  to be in contact with the connecting adhesive pattern  64 , and external and internal resonant electrode patterns  34 ,  38 ,  54  and  58 . The connecting adhesive pattern  64  (corresponding to the connecting adhesive layer  24 ) may be disposed between the internal resonant electrode patterns  54  and  58 . 
         [0044]    The internal resonant electrode patterns  54  and  58  may be disposed on one side of the respective facing surfaces between the resonant patterns  44  and  48  to face each other as illustrated in  FIG. 6 . The external resonant electrode patterns  34  and  38  may be formed on opposite surfaces to the facing surfaces between the resonant patterns  44  and  48  to overlap the other side of the facing surfaces of the resonant patterns  44  and  48 . The external resonant electrode patterns  34  and  38  may or may not overlap the internal resonant electrode patterns  54  and  58 . The external and internal resonant electrode patterns  34 ,  38 ,  54  and  58  correspond to the internal and external substrate electrode patterns  16  and  18 , respectively. 
         [0045]    Forming the piezoelectric resonant patterns comprises sequentially cutting the green substrates along lines A 1 -A 2 , A 3 -A 4 , A 5 -A 6 , A 7 -A 8  and A 9 -A 10  passing between the internal and external substrate electrode patterns  16  and  18 , and along line B 1 -B 2  crossing the internal and external substrate electrode patterns  16  and  18  as illustrated in  FIG. 6 . Alternatively, forming the piezoelectric resonant patterns may comprise sequentially cutting the green substrates along line B 1 -B 2  crossing the internal and external substrate electrode patterns  16  and  18 , and along lines A 1 -A 2 , A 3 -A 4 , A 5 -A 6 , A 7 -A 8  and A 9 -A 10  passing between the internal and external substrate electrode patterns  16  and  18 . 
         [0046]    Referring to  FIGS. 6 and 7 , when two green bodies  2  and  4  are prepared, a piezoelectric resonator  80  having connection electrodes  74  and  78 , between the internal resonant electrode patterns  54  and  58  and between the external resonant electrode patterns  34  and  38  to be disposed on the piezoelectric resonant pattern  70 , is formed according to the first and second embodiments of the present invention. Each of the connection electrodes  74  and  78  may be formed of at least one conductive layer. Here, the connection electrodes  74  and  78  may be in contact with the external resonant electrode patterns  34  and  38 , the resonant patterns  44  and  48 , and the internal resonant electrode patterns  54  and  58 , the connecting adhesive pattern  64  and the insulating adhesive pattern  68 . Here, the connection electrodes  74  and  78 , between which the resonant patterns  44  and  48  are disposed, are electrically isolated from each other. The connection electrodes  74  and  78  may be formed to have the same or different thicknesses due to the structure of the piezoelectric resonant pattern  70 . 
         [0047]    Meanwhile, when two or more even number of green bodies are prepared, a piezoelectric resonator  80  having connection electrodes  74  and  78 , between the internal resonant electrode patterns  54  and  58  and between the external resonant electrode patterns  34  and  38  to be disposed on the piezoelectric resonant pattern  70 , is provided according to the second embodiment of the present invention equivalent to the first embodiment of the present invention. Also, pairs of substrates are repeatedly selected from the rest of the green substrates, forming the internal and external substrate electrode patterns  16  and  18  thereon, forming the adhesive agent  29 , forming the piezoelectric resonant pattern  70 , and forming the piezoelectric resonator  80 , sequentially. Also, the third embodiment of the present invention, unlike the first and second embodiments of the present invention, may provide several piezoelectric resonators  80  having connection electrodes  74  and  78 , which are disposed on one piezoelectric resonant pattern  70  repeatedly selected from the piezoelectric resonant patterns to connect the external resonant electrode patterns  34  and  38  to each other, and the internal resonant electrode patterns  54  and  58  to each other. According to the second and third embodiments of the present invention, the connection electrodes  74  and  78  may be formed to have the same or different thicknesses due to the structure of the piezoelectric resonant pattern  70 . 
         [0048]      FIG. 8  is a cross-sectional view of a multilayered piezoelectric resonant device having the piezoelectric resonator of  FIG. 7 , and  FIG. 9  is a cross-sectional view of a cap-shaped piezoelectric resonant device having the piezoelectric resonator of  FIG. 7 . 
         [0049]    Referring to  FIGS. 7 and 8 , a protection cap  115 , a resonant base  94  and a piezoelectric resonator  80  are prepared. The piezoelectric resonator  80  may be formed according to one selected from the first to fourth embodiments of the present invention. The resonant base  94  may be formed of a ceramic material. The resonant base  94  has a resonant groove  98 , the resonant groove  98  having sidewalls SW 1  and SW 2  spaced apart form each other. A mounting surface  1  MS 1  is disposed between the sidewalls SW 1  and SW 2  of the resonant groove  94 . Subsequently, a protection adhesive layer  105  is formed on the resonant base  94 . The protection adhesive layer  105  may be formed on the resonant base  94  to surround the resonant groove  98 , and the protection adhesive layer  105  may be formed of an insulating material. 
         [0050]    The piezoelectric resonator  80  is mounted on the resonant base  94 . Here, the piezoelectric resonator  80  may be disposed on the mounting surface  1  MS 1  of the resonant groove  98 . As a result, the piezoelectric resonator  80  may be electrically connected to the resonant base  94  using the connection electrodes  74  and  78 . Also, the protection cap  115  is formed on the resonant base  94 . The protection cap  115  may be formed of a ceramic material. Here, the protection cap  115  may be attached to the resonant base  94  with the protection adhesive layer  105 . Therefore, the protection cap  115 , the piezoelectric resonator  80 , and the resonant base  94  may constitute a multilayered piezoelectric resonant device  120 . 
         [0051]    Referring to  FIGS. 7 and 9 , a protection cap  145 , a plate base  125  and a piezoelectric resonator  80  are prepared. The piezoelectric resonator  80  may be formed according to one selected from the first to fourth embodiments of the present invention. The plate base  125  may be formed of a ceramic material. The plate base  125  has a mounting surface  2  MS 2 . Subsequently, the piezoelectric resonator  80  is mounted on the plate base  125 . Here, the piezoelectric resonator  80  may be disposed on the mounting surface  2  MS 2  of the plate base  125 . Therefore, the piezoelectric resonator  80  may be electrically connected to the plate base  125  using connection electrodes  74  and  78 . 
         [0052]    A protection adhesive layer  135  is formed on the plate base  125 . The protection adhesive layer  135  may be formed on the plate base  125  to surround the piezoelectric resonator  80 . The protection adhesive layer  135  may be formed of an insulating material. Here, the protection cap  145  may be attached on the plate base  125  with the protection adhesive layer  135 . Therefore, the protection cap  145 , the piezoelectric resonator  80  and the plate base  125  may constitute a cap-shaped piezoelectric resonant device  150 . 
         [0053]    As described above, the invention provides methods of forming a piezoelectric resonant device having a piezoelectric resonator. Accordingly, green bodies are sintered and grinded in advance, thereby minimizing an effect of the production process on the green bodies, which may improve an electrical characteristic of the piezoelectric resonator. 
         [0054]    Exemplary embodiments of the present invention have been disclosed herein and, although specific terms are employed, they are used and are to be interpreted in a generic and descriptive sense only and not for purpose of limitation. Accordingly, it will be understood by those of ordinary skill in the art that various changes in form and details may be made without departing from the spirit and scope of the present invention as set forth in the following claims.