Abstract:
The present invention provides a novel method of producing piezoelectric vibration pieces in which a plurality of piezoelectric vibration pieces are formed at once from a wafer, using a plurality of photoresist processes. The wafer is marked with wafer marks each unique to a different one of photoresist masks to prevent a wrong use of the photoresist masks during the photoresist processes.

Description:
RELATED APPLICATIONS 
       [0001]    This application claims priority under 35 U.S.C. §119 to Japanese Patent Application No. 2010-222193 filed on Sep. 30, 2010, the entire content of which is hereby incorporated by reference. 
       BACKGROUND OF THE INVENTION 
       [0002]    1. Field of the Invention 
         [0003]    The present invention relates to a method of manufacturing a piezoelectric vibrating piece, a wafer, a piezoelectric vibrator, an oscillator, an electronic apparatus, and a radio-controlled timepiece. 
         [0004]    2. Description of the Related Art 
         [0005]    In recent years, a piezoelectric vibrator which has a piezoelectric vibrating piece using crystal or the like is used in a mobile phone or a portable information terminal apparatus as a time source, a timing source of a control signal, a reference signal source, or the like. This type of piezoelectric vibrating piece includes a piezoelectric plate which is made of a piezoelectric material, and an electrode portion which vibrates the piezoelectric plate when a voltage is applied. The electrode portion has a plurality of electrode films which are laminated on the outer surface of the piezoelectric plate and have different patterns. 
         [0006]    In regard to this piezoelectric vibrating piece, in general, a plurality of piezoelectric vibrating pieces are manufactured using a wafer at one time. As an example of a manufacturing method, for example, a method described in JP-A-2007-142795 is used. According to this method, after the exterior shape of a piezoelectric substrate and an alignment marker are formed in a wafer, the electrode portion is formed. 
         [0007]    When forming the electrode films of the electrode portion, first, a resist film is applied onto the wafer, and a photomask is arranged on the wafer to pattern the resist film, thereby forming a resist pattern. Thereafter, an electrode film is formed on the basis of the resist pattern. In this course, when the photomask is arranged on the wafer, the photomask is aligned on the wafer using the alignment marker, making it possible to form the electrode portion with high precision. 
         [0008]    As described above, when the electrode portion has a plurality of electrode films having different patterns, in order to form resist patterns having different shapes to correspond to the electrode films, it is necessary to use a plurality of types of photomasks. 
         [0009]    In the method of manufacturing a piezoelectric vibrating piece in the related art, however, a photomask of a different type from a photomask which should be originally arranged may be arranged to form a resist pattern. In this case, the electrode film is not patterned in a desired pattern, and the wafer is disused or the like, causing an increase in manufacturing cost. 
       SUMMARY OF THE INVENTION 
       [0010]    The invention has been finalized in consideration of the above-described situation, and an object of the invention is to provide a method of manufacturing a piezoelectric vibrating piece capable of preventing a resist pattern from being formed in a state where a mask member is erroneously arranged, thereby achieving low cost. 
         [0011]    In order to solve the above-described problem, the invention suggests the following means. 
         [0012]    An aspect of the invention provides a method of manufacturing a piezoelectric vibrating piece which forms a piezoelectric vibrating piece. The piezoelectric vibrating piece includes a piezoelectric plate which is made of a piezoelectric material, and an electrode portion which vibrates piezoelectric plate when a voltage is applied. The electrode portion has a plurality of electrode films which are laminated on the outer surface of the piezoelectric plate and have different patterns. The method includes an electrode forming step of forming the electrode portion in a wafer in which the outline shape of the piezoelectric plate is formed. The electrode forming step has a plurality of electrode film forming steps of forming the plurality of electrode films in the wafer by a photolithography technique. Each of the plurality of electrode film forming steps has a resist pattern forming step of applying a resist film onto the wafer, arranging a mask member prepared for one electrode film to be formed in the electrode film forming step from among a plurality of mask members prepared for the electrode films in the wafer, and irradiating light through the mask member to form a resist pattern. In the resist pattern forming step, the mask member is arranged in the wafer while a mask-side mark formed in the mask member prepared for one electrode film is aligned with wafer-side marks corresponding to the mask member from among a plurality of wafer-side marks formed in the wafer. The mask-side mark has a pair of mark portions formed at an interval in the mask member, and the interval between the pair of mark portions differs between the plurality of mask members. Each of the plurality of wafer-side marks has a pair of concave portions at an interval in the wafer, and the interval between the pair of concave portions differs between the plurality of wafer-side marks such that the wafer-side marks have the same interval as the interval between the pair of mark portions in the corresponding mask member. 
         [0013]    Another aspect of the invention provides a wafer which is used for the method of manufacturing a piezoelectric vibrating piece. A plurality of wafer-side marks are formed to correspond to the plurality of mask members. Each of the plurality of wafer-side marks has a pair of concave portions at an interval, and the interval between the pair of concave portions differs between the plurality of wafer-side marks such that the wafer-side marks have the same interval as the interval between the pair of mask portions. 
         [0014]    According to the invention, the interval between a pair of concave portions differs between a plurality of wafer-side marks such that the wafer-side marks have the same interval as the interval between a pair of mark portions in the corresponding mask member. For this reason, during the resist pattern forming step, even when the mark portions of a mask member different from a mask member prepared for one electrode film are aligned with the concave portions of the wafer-side marks corresponding to the mask member prepared for one electrode film, one of a pair of mark portions is shifted from the concave portions. Therefore, it becomes possible to prevent a resist pattern from being formed in a state where different types of mask members are arranged, thereby suppressing the disuse or the like of a wafer and achieving low cost of a piezoelectric vibrating piece. 
         [0015]    In the method of manufacturing a piezoelectric vibrating piece, the mark portions may be the exposure openings which pass through the mask member, and the shape of each of the concave portions in plan view may be the same as the shape of each of the exposure openings in plan view. In the resist pattern forming step, the concave portions may be exposed from the exposure openings to align the mask-side mark with the wafer-side marks. 
         [0016]    In this case, during the resist pattern forming step, the concave portions are exposed from the exposure openings to align the mask-side mark with the wafer-side marks, thereby reliably obtaining the above-described functional effects. 
         [0017]    In the method of manufacturing a piezoelectric vibrating piece, the shapes of the exposure openings in plan view may be asymmetrical in both directions of one direction in which a pair of exposure openings are distant from each other and another direction along the surface of the mask member and perpendicular to one direction. 
         [0018]    In this case, the shapes of the exposure openings in plan view are asymmetrical in both directions of one direction and another direction. For this reason, during the resist pattern forming step, although the concave portions are exposed from the exposure opening in a state where the mask member is inversed in one direction with respect to a normal direction or is inversed in another direction, such that the entire concave portions cannot be exposed. Therefore, it is possible to prevent a resist pattern from being formed in a state where a mask member is arranged in a different direction. 
         [0019]    In the method of manufacturing a piezoelectric vibrating piece, in the resist pattern forming step, a coating member may be arranged on the wafer, and a resist film may be applied while the concave portions of the wafer-side marks corresponding to the mask member prepared for one electrode film are covered with the coating member. 
         [0020]    In this case, during the resist pattern forming step, the resist film is applied while the concave portions are covered with the coating member. Therefore, it is possible to suppress unclearness of the shape of the concave portion in plan view due to the application of the resist film, and to reliably align the mark portion with the concave portions. 
         [0021]    According to another aspect of the invention, a piezoelectric vibrator includes a piezoelectric vibrating piece which is manufactured by the method of manufacturing a piezoelectric vibrating piece. 
         [0022]    According to the invention, piezoelectric vibrator includes a piezoelectric vibrating piece which is manufactured by the method of manufacturing a piezoelectric vibrating piece, thereby achieving low cost. 
         [0023]    Another aspect of the invention provides an oscillator in which the piezoelectric vibrator is electrically connected to an integrated circuit as an oscillating element. 
         [0024]    Another aspect of the invention provides an electronic apparatus in which the piezoelectric vibrator is electrically connected to a timepiece unit. 
         [0025]    Another aspect of the invention provides a radio-controlled timepiece in which the piezoelectric vibrator is electrically connected to a filter unit. 
         [0026]    According to the invention, the oscillator, the electronic apparatus, and the radio-controlled timepiece of the invention include the piezoelectric vibrator, thereby manufacturing an oscillator, an electronic apparatus, and a radio-controlled timepiece at low cost. 
         [0027]    According to the method of manufacturing a piezoelectric vibrating piece and the wafer of the invention, it is possible to prevent a resist pattern from being formed in a state where a mask member is erroneously arranged, thereby achieving low cost. 
         [0028]    According to the piezoelectric vibrator, the oscillator, the electronic apparatus, and the radio-controlled timepiece of the invention, low cost can be achieved. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0029]      FIG. 1  is a diagram showing the content of a case of a piezoelectric vibrator according to an embodiment of the invention when the piezoelectric vibrating piece is viewed in plan view; 
           [0030]      FIG. 2  is a plan view when the piezoelectric vibrating piece shown in  FIG. 1  is viewed from above; 
           [0031]      FIG. 3  is a plan view when the piezoelectric vibrating piece shown in  FIG. 1  is viewed from below; 
           [0032]      FIG. 4  is a perspective view of the piezoelectric vibrating piece shown in  FIG. 1 ; 
           [0033]      FIG. 5  is a sectional view taken along the line A-A of  FIG. 2 ; 
           [0034]      FIG. 6  is a sectional view taken along the line B-B of  FIG. 1 ; 
           [0035]      FIG. 7  is a sectional view taken along the line C-C of  FIG. 2 ; 
           [0036]      FIG. 8  is a plan view of an outline mask which constitutes an apparatus for manufacturing a piezoelectric vibrating piece, which is used for a method of manufacturing a piezoelectric vibrating piece according to the invention; 
           [0037]      FIG. 9  is a plan view of a first mask which constitutes an apparatus for manufacturing a piezoelectric vibrating piece, which is used for a method of manufacturing a piezoelectric vibrating piece according to the invention; 
           [0038]      FIG. 10  is a plan view of a second mask which constitutes an apparatus for manufacturing a piezoelectric vibrating piece, which is used for a method of manufacturing a piezoelectric vibrating piece according to the invention; 
           [0039]      FIG. 11  is a flowchart of a method of manufacturing a piezoelectric vibrating piece according to the invention; 
           [0040]      FIG. 12  is a process view showing a method of manufacturing a piezoelectric vibrating piece, and a sectional view corresponding to the line C-C of  FIG. 2 ; 
           [0041]      FIG. 13  is a process view showing a method of manufacturing a piezoelectric vibrating piece, and a plan view of a wafer; 
           [0042]      FIG. 14  is a process view showing a method of manufacturing a piezoelectric vibrating piece, and a plan view of a wafer; 
           [0043]      FIG. 15  is a process view showing a method of manufacturing a piezoelectric vibrating piece, and a sectional view corresponding to the line C-C of  FIG. 2 ; 
           [0044]      FIG. 16  is a process view showing a method of manufacturing a piezoelectric vibrating piece, and a plan view of a wafer; 
           [0045]      FIG. 17  is a process view showing a method of manufacturing a piezoelectric vibrating piece, and a plan view of a wafer; 
           [0046]      FIG. 18  is a diagram illustrating the action of a method of manufacturing a piezoelectric vibrating piece, and a plan view showing a state where, during a resist pattern forming step, a resist film is applied while through holes are not covered with a coating member; 
           [0047]      FIG. 19  is a process view showing a method of manufacturing a piezoelectric vibrating piece, and a sectional view corresponding to the line C-C of  FIG. 2 ; 
           [0048]      FIG. 20  is a process view showing a method of manufacturing a piezoelectric vibrating piece, and a sectional view corresponding to the line C-C of  FIG. 2 ; 
           [0049]      FIG. 21  is a process view showing a method of manufacturing a piezoelectric vibrating piece, and a plan view of a wafer; 
           [0050]      FIG. 22  is a process view showing a method of manufacturing a piezoelectric vibrating piece, and a sectional view corresponding to the line C-C of  FIG. 2 ; 
           [0051]      FIG. 23  is a process view showing a method of manufacturing a piezoelectric vibrating piece, and a plan view of a wafer; 
           [0052]      FIG. 24  is a process view showing a method of manufacturing a piezoelectric vibrating piece, and a plan view of a wafer; 
           [0053]      FIG. 25  is a process view showing a method of manufacturing a piezoelectric vibrating piece, and a sectional view corresponding to the line C-C of  FIG. 2 ; 
           [0054]      FIG. 26  is a process view showing a method of manufacturing a piezoelectric vibrating piece, and a sectional view corresponding to the line C-C of  FIG. 2 ; 
           [0055]      FIG. 27  is a process view showing a method of manufacturing a piezoelectric vibrating piece, and a plan view of a wafer; 
           [0056]      FIG. 28  is a diagram illustrating the action of a method of manufacturing a piezoelectric vibrating piece, and a plan view when a first mask is inversed; 
           [0057]      FIG. 29  is a configuration diagram showing an oscillator according to an embodiment of the invention; 
           [0058]      FIG. 30  is a configuration diagram showing an electronic apparatus according to an embodiment of the invention; 
           [0059]      FIG. 31  is a configuration diagram showing a radio-controlled timepiece according to an embodiment of the invention; 
           [0060]      FIG. 32  is a plan view showing a modification of exposure openings and through holes which are used for a method of manufacturing a piezoelectric vibrating piece according to the invention; 
           [0061]      FIG. 33  is a plan view showing a modification of exposure openings and through holes which are used for a method of manufacturing a piezoelectric vibrating piece according to the invention; 
           [0062]      FIG. 34  is a plan view showing a modification of exposure openings and through holes which are used for a method of manufacturing a piezoelectric vibrating piece according to the invention; and 
           [0063]      FIG. 35  is a plan view showing a modification of exposure openings and through holes which are used for a method of manufacturing a piezoelectric vibrating piece according to the invention. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0064]    Hereinafter, an embodiment of the invention will be described with reference to the drawings. 
         [0065]    As shown in  FIG. 1 , a piezoelectric vibrator  1  is a cylinder package type piezoelectric vibrator, and includes a tuning fork type piezoelectric vibrating piece  2 , a plug  4  in which the piezoelectric vibrating piece  2  is mounted, and a case  3  which seals the piezoelectric vibrating piece  2  airtight along with the plug  4 . 
         [0066]    As shown in  FIGS. 2 and 3 , the piezoelectric vibrating piece  2  is a tuning fork type vibrating piece which is formed of a piezoelectric material, such as crystal, lithium tantalate, or lithium niobate, and vibrates when a predetermined voltage is applied. 
         [0067]    The piezoelectric vibrating piece  2  includes a piezoelectric plate  11  which has a pair of vibrating arm portions  8  and  9  arranged in parallel with each other and a base portion  10  fixing the base ends of a pair of vibrating arm portions  8  and  9  as a single body, an excitation electrode  14  which has a first excitation electrode  12  and the second excitation electrode  13  formed on the outer surfaces of a pair of vibrating arm portions  8  and  9  to vibrate a pair of vibrating arm portions  8  and  9 , and mount electrodes  15  and  16  which are electrically connected to the first excitation electrode  12  and the second excitation electrode  13 . 
         [0068]    The piezoelectric vibrating piece  2  of this embodiment also includes groove portion  17  which are formed on both principal surfaces of a pair of vibrating arm portions  8  and  9  at a length L from the base end portions of the vibrating arm portions  8  and  9  toward the front end portions. As shown in  FIG. 4 , the groove portions  17  are formed from the base end portions of the vibrating arm portions  8  and  9  to substantially near the middle. The widths of a pair of vibrating arm portions  8  and  9  are W in common. A portion of the base portion  10  which is connected to the base end portions of a pair of vibrating arm portions  8  and  9  is referred to as a crotch portion  10   a.    
         [0069]    As shown in  FIGS. 2 ,  3 , and  5 , the excitation electrode  14  having the first excitation electrode  12  and the second excitation electrode  13  is an electrode which vibrates a pair of vibrating arm portions  8  and  9  at a predetermined resonance frequency in a direction close to each other or distant from each other. The first excitation electrode  12  and the second excitation electrode  13  are patterned on the outer surfaces of a pair of vibrating arm portions  8  and  9  in a state of being electrically separated from each other. Specifically, the first excitation electrode  12  is mainly formed the groove portion  17  of the vibrating arm portion  8  and on both lateral surfaces of the vibrating arm portion  9 , and the second excitation electrode  13  is mainly formed on both lateral surfaces of the vibrating arm portion  8  and on the groove portion  17  of the vibrating arm portion  9 . 
         [0070]    As shown in  FIGS. 2 and 3 , the first excitation electrode  12  and the second excitation electrode  13  are continuously formed on both principal surfaces of the base portion  10 , and are respectively connected to the mount electrodes  15  and  16  through extraction electrodes  19  and  20 . The mount electrodes  15  and  16  are formed at the base end of the piezoelectric plate  11 . That is, the excitation electrode  14 , the mount electrodes  15  and  16 , and the extraction electrodes  19  and  20  function as an electrode portion (laminate)  18  which vibrates a pair of vibrating arm portions  8  and  9  when a predetermined voltage is applied. 
         [0071]    As shown in  FIGS. 6 and 7 , the electrode portion  18  has a base metal layer (electrode film)  18   a  made of chromium (Cr) and a finish metal layer (electrode film)  18   b  made of gold (Au) sequentially laminated on the outer surface of the piezoelectric plate  11 . The metal layers  18   a  and  18   b  have different patterns. 
         [0072]    The base metal layer  18   a  is provided to improve adhesiveness between the finish metal layer  18   b  and the piezoelectric vibrating piece  2 . 
         [0073]    With regard to the finish metal layer  18   b,  as shown in  FIGS. 4 ,  5 , and  7 , a part of or the entire part of the finish metal layer  18   b  is removed in a region from the base end portions to the front end portions in the vibrating arm portions  8  and  9 . Specifically, on the front end portion side with respect to the base end portion of each of the vibrating arm portions  8  and  9 , the entire part of the finish metal layer  18   b  is removed to a position at equal to or greater a length L from the base end portion (a region RA shown in  FIG. 4 ). On the base portion  10  side with respect to the base end portion of each of the vibrating arm portions  8  and  9 , the entire part of the finish metal layer  18   b  is removed to a position at a distance twice the width W of each of the vibrating arm portions  8  and  9  from the base end portion toward the base portion  10  (a region RB shown in  FIG. 4 ). 
         [0074]    That is, the electrode portion  18  is formed of the base metal layer  18   a  over the region RA and the region RB, where the groove portions  17  of the vibrating arm portions  8  and  9  are formed, including the inside of the groove portions  17 . In the region RA and the region RB, an insulating film  34  made of silicon oxide (SiO2) or the like is coated to cover the base metal layer  18   a.  Thus, even when conductive particles are stuck between the excitation electrodes  12  and  13  of the vibrating arm portions  8  and  9 , it is possible to prevent short-circuit between the electrodes. 
         [0075]    In this embodiment, a single-layered region R which is the total region of the region RA and the region RB is a region where the excitation electrodes  12  and  13  are formed. In the single-layered region R, an insulating film  34  is formed on the base metal layer  18   a  in a state where the finish metal layer  18   b  is removed, thereby improving adhesiveness of the insulating film  34  and reliably preventing short-circuit of the excitation electrodes  12  and  13 . 
         [0076]    As described above, with regard to the extraction electrodes  19  and  20  and the mount electrodes  15  and  16  which are formed on the base end side with respect to the single-layered region R in the piezoelectric plate  11 , the base metal layer  18   a  and the finish metal layer  18   b  are laminated. Hereinafter, a region where the base metal layer  18   a  and the finish metal layer  18   b  is referred to as a laminated region P. 
         [0077]    At the front end of each of a pair of vibrating arm portions  8  and  9 , a weight metal film  21  is formed to perform adjustment (frequency adjustment) such that the vibration state of the vibrating arm portion is within a predetermined frequency range. The weight metal film  21  is divided into a rough adjustment film  21   a  which is used to roughly adjust frequency and a fine adjustment film  21   b  which is used to finely adjust frequency. With frequency adjustment using the rough adjustment film  21   a  and the fine adjustment film  21   b,  it is possible to make the frequency of each of a pair of vibrating arm portions  8  and  9  be in the nominal frequency range of a device. 
         [0078]    As shown in  FIG. 1 , the case  3  is formed in the shape of a bottomed cylinder, is press-fit to the outer circumference of a stem  30  (described below) of the plug  4  in a state where the piezoelectric vibrating piece  2  is accommodated therein, and is fixedly engaged. Press-fitting of the case  3  is done in a vacuum atmosphere, and a space which surrounds the piezoelectric vibrating piece  2  in the case  3  is maintained under vacuum. 
         [0079]    The plug  4  has a stem  30  which hermetically seals the case  3 , two lead terminals  31  which are arranged in parallel with each other to pass through the stem  30 , and an insulating filling material  32  which is filled inside the stem  30  to fix the stem  30  and the lead terminals  31 . 
         [0080]    The stem  30  is formed of a metal material in an annular shape. The filling material  32  is made of, for example, borosilicate glass. The surfaces of the lead terminals  31  and the outer circumference of the stem  30  are coated with plating  35  (described below) made of the same material. 
         [0081]    With regard to the two lead terminals  31 , a portion which protrudes inward of the case  3  becomes an inner lead  31   a , and a portion which protrudes outward of the case  3  becomes an outer lead  31   b.  The lead terminals  31  has a diameter of, for example, about 0.12 mm, and as the base material of the lead terminals  31 , kovar (FeNiCo alloy) is commonly used. As shown in  FIG. 6 , the outer surfaces of the lead terminals  31  and the outer circumference of the stem  30  are coated with the plating  35 . As the material for the plating to be coated, copper (Cu) plating or the like is used as a base film  35   a,  and solder plating (alloy of tin and lead having a weight ratio of 1:9) having a high melting point of, for example, 300 degrees, is used as a finish film  35   b.    
         [0082]    Cold pressure welding is carried out under vacuum on the inner circumference of the case  3  while interposing the plating  35  coated on the outer circumference of the stem  30 , such that the inside of the case  3  is sealed airtight in a vacuum state. 
         [0083]    As shown in  FIG. 7 , the inner leads  31   a  and the mount electrodes  15  and  16  are mounted on the finish metal layer  18   b  through joints E formed by melting the finish film (high-melting-point solder plating)  35   b.  That is, the inner leads  31   a  and the mount electrodes  15  and  16  are mechanically bonded to each other and electrically connected to each other through the joints E. As a result, the piezoelectric vibrating piece  2  is mounted on the two lead terminals  31 . 
         [0084]    The above-described two lead terminals  31  function as external connection terminals which have one end (outer lead  31   b ) electrically connected to the outside and the other end (inner lead  31   a ) mounted with the piezoelectric vibrating piece  2 . 
         [0085]    When the piezoelectric vibrator  1  configured as above is activated, a predetermined driving voltage is applied to the outer leads  31   b  of the two lead terminals  31 . Thus, a current can flow in the excitation electrode  14  having the first excitation electrode  12  and the second excitation electrode  13  through the inner leads  31   a,  the joints E, the mount electrodes  15  and  16 , and the extraction electrodes  19  and  20 , thereby vibrating a pair of vibrating arm portions  8  and  9  at a predetermined frequency in a direction close to each other or distant from each other. With the use of the vibration of a pair of vibrating arm portions  8  and  9 , the piezoelectric vibrator can be used as a time source, a timing source of a control signal, a reference signal source, or the like. 
       (Method of Manufacturing Piezoelectric Vibrating Piece) 
       [0086]    Next, description will be provided as to a method which forms the above-described piezoelectric vibrating piece  2  using a wafer S (see  FIG. 12 ) made of a piezoelectric material. 
         [0087]    Initially, an apparatus  40  for manufacturing a piezoelectric vibrating piece which is used in this manufacturing method will be described. 
         [0088]    As shown in  FIGS. 8 to 10 , the manufacturing apparatus  40  includes an outline mask  41  which forms the outline shape of the piezoelectric plate  11  in a wafer S, and two (multiple) electrode film masks (mask member)  42  and  43  which are respectively prepared for the base metal layer  18   a  and the finish metal layer  18   b.    
         [0089]    The masks  41 ,  42 , and  43  respectively include frame portions  41   b,    42   b , and  43   b  which define exposure regions  41   a,    42   a,  and  43   a,  and a plurality of coated portions  41   c,    42   c,  and  43   c  which are arranged in the exposure regions  41   a,    42   a , and  43   a  and connected to the frame portions  41   b,    42   b,  and  43   b  through connection portions (not shown). 
         [0090]    The outline shapes of the frame portions  41   b,    42   b,  and  43   b  of the masks  41 ,  42 , and  43  and the exposure regions  41   a,    42   a,  and  43   a  are all a rectangle in plan view, and in the example of the drawing, a square in plan view. The frame portions  41   b,    42   b,  and  43   b  and the exposure regions  41   a,    42   a,  and  43   a  are arranged coaxially with the axes of the masks  41 ,  42 , and  43 . 
         [0091]    The coated portion  41   c  of the outline mask  41  is formed to follow the outline shape of the piezoelectric plate  11 . The coated portion  42   c  of the first mask  42  prepared for the base metal layer  18   a  from among the two electrode film masks  42  and  43  is formed to follow the outline shape of the base metal layer  18   a . The coated portion  43   c  of the first mask  43  for the finish metal layer  18   b  is formed to follow the outline shape of the finish metal layer  18   b.    
         [0092]    In the masks  41 ,  42 , and  43  shown in  FIGS. 8 to 10 , for ease of understanding, the shape of each of the coated portions  41   c,    42   c,  and  43   c  is simplified, and the number of coated portions  41   c,    42   c,  and  43   c  is omitted. 
         [0093]    As shown in  FIG. 8 , in the frame portion  41   b  of the outline mask  41 , two marks forming portions  41   d  and  41   e  are formed to form two wafer-side marks S 3  and S 4  (see  FIG. 13 ) corresponding to the two electrode film masks  42  and  43  in the wafer S. The mark forming portions  41   d  and  41   e  respectively have a pair of mark openings  41   f  and  41   g  which pass through the frame portion  41   b.    
         [0094]    A pair of mark openings  41   f  and  41   g  are arranged at an interval, and in the example of the drawing, are respectively arranged in the opposing portions of the frame portion  41   b  with the axis of the outline mask  41  interposed therebetween. In this embodiment, one direction in which a pair of mark openings  41   f  and  41   g  are distant from each other is in parallel with one side of the frame portion  41   b.    
         [0095]    A pair of mark openings  41   f  of the first mark forming portion  41   d  from the two mark forming portions  41   d  and  41   e  are arranged to be shifted with respect to a pair of mark openings  41   g  in the second mark forming portion  41   e  in another direction along the surface of the outline mask  41  and perpendicular to one direction. 
         [0096]    The interval between a pair of mark openings  41   f  and  41   g  differs between the two mark forming portions  41   d  and  41   e.    
         [0097]    The shapes of the mark openings  41   f  and  41   g  in plan view are asymmetrical in both directions of one direction and another direction. In the example of the drawing, the shape of each of the mark openings  41   f  and  41   g  is an L shape in which linear portions extending in one direction and another direction are connected to each other. 
         [0098]    As shown in  FIGS. 9 and 10 , mask-side marks  42   d  and  43   d  are respectively formed in the frame portions  42   b  and  43   b  of the two electrode film masks  42  and  43 . In this embodiment, the mask-side marks  42   d  and  43   d  respectively have pairs of exposure openings (mark portions)  42   f  and  43   f  which are formed at an interval in the electrode film masks  42  and  43  to pass through the electrode film masks  42  and  43 . 
         [0099]    The mask-side marks  42   d  and  43   d  differ between the two electrode film masks  42  and  43 . In this embodiment, the interval between the pairs of exposure openings  42   f  and  43   f  differs between the two electrode film masks  42  and  43 . 
         [0100]    As shown in  FIG. 9 , the mask-side mark  42   d  formed in the first mask  42  corresponds to the first mark forming portion  41   d  of the outline mask  41 , and the interval between a pair of exposure openings  42   f  in the mask-side mark  42   d  of the first mask  42  is the same as the interval between a pair of mark openings  41   f  in the first mark forming portion  41   d  of the outline mask  41 . 
         [0101]    The shape of each of the exposure openings  42   f  in plan view is the same as the shape of the first mark forming portion  41   d  in plan view. In this embodiment, the shapes of the exposure openings  42   f  in plan view are asymmetrical in both directions of one direction in which a pair of exposure openings  42   f  are distant from each other and another direction along the surface of the first mask  42  and perpendicular to one direction. The shape of each of the exposure openings  42   f  in plan view is an L shape in which linear portions extending in one direction and another direction are connected to each other. 
         [0102]    As shown in  FIG. 10 , the mask-side mark  43   d  formed in the second mask  43  corresponds to the second mark forming portion  41   e  of the outline mask  41 , and the interval between a pair of exposure openings  43   f  in the mask-side mark  43   d  of the second mask  43  is the same as the interval between a pair of mark openings  41   g  in the second mark forming portion  41   e.    
         [0103]    The shape of each of the exposure openings  43   f  in plan view is the same as the shape of the second mark forming portion  41   e  in plan view. In this embodiment, the shapes of the exposure openings  43   f  in plan view are asymmetrical in both directions of one direction in which a pair of exposure openings  43   f  are distant from each other and another direction along the surface of the second mask  43  and perpendicular to one direction. The shape of each of the exposure openings  43   f  in plan view is an L shape in which linear portions extending in one direction and another direction are connected to each other. 
         [0104]    Next, a method of manufacturing a piezoelectric vibrating piece which forms the piezoelectric vibrating piece  2  using the apparatus  40  for manufacturing a piezoelectric vibrating piece will be described with reference to  FIG. 11 . 
         [0105]    First, as shown in  FIG. 12 , a Lambert raw stone of crystal is sliced at a predetermined angle to form a wafer S having a constant thickness. Subsequently, the wafer S is wrapped and subjected to rough processing. Thereafter, the affected layer is removed by etching, and mirror grinding processing, such as polishing, is performed to form the wafer S having a predetermined thickness (S 10 ). 
         [0106]    Next, an outline forming step of forming the outline shapes of a plurality of piezoelectric plates  11  in the wafer S after polishing is performed (S 20 ). 
         [0107]    At this time, first, a protective film in which, for example, a chromium layer, a gold layer, and the like are laminated is laminated on both surfaces of the wafer S by, for example, sputtering or the like. Thereafter, a positive type resist film (not shown) is applied onto both surfaces of the wafer S from above the protective film, and the outline mask  41  is arranged above the resist film. 
         [0108]    Light is irradiated onto the resist film through the outline mask  41 , and a resist pattern is exposed to the resist film. After the outline mask  41  is detached, the resist film is developed to remove an exposed portion. Thereafter, metal etching is performed to remove the protective film exposed from the exposed portion. At the same time the resist film is removed, crystal etching is performed to etch the wafer S exposed from the removed portion of the protective film. Thereafter, the protective film is removed, and the outline forming step ends. 
         [0109]    The outline forming step is performed, such that, as shown in  FIG. 13 , the outline shapes of the piezoelectric plates  11  are formed in the wafer S. The shape of the wafer S in plan view is a rectangle, and in the example of the drawing, a square, and the outline shape of the piezoelectric plate  11  is formed within a plate forming region S 2  inward of the outer circumferential portion S 1  of the wafer S. A plate forming region S 2  is a portion exposed from the exposure region  41   a  of the outline mask  41 . In the plate forming region S 2 , the outline shape of the piezoelectric plate  11  and a portion excluding a connection portion (not shown) which connects the outline shape and the outer circumferential portion S 1  are removed by the crystal etching. 
         [0110]    In this embodiment, since the mark forming portions  41   d  and  41   e  are formed in the outline mask  41 , during the outline forming step, the two wafer-side marks S 3  and S 4  corresponding to the two electrode film masks  42  and  43  are formed in the wafer S simultaneously with the outline shape of the piezoelectric plate  11 . 
         [0111]    During the outline forming step, when the outline mask  41  is arranged above the resist film, the two wafer-side marks S 3  and S 4  are formed in the portions exposed from the mark forming portions  41   d  and  41   e . The wafer-side marks S 3  and S 4  respectively have a pair of through holes (concave portions) S 5  and S 6  formed at an interval in the wafer S. 
         [0112]    A pair of through holes S 5  and S 6  are respectively arranged in the opposing portions of the outer circumferential portion S 1  of the wafer S with the axis of the wafer S interposed therebetween. In this embodiment, one direction in which a pair of through holes S 5  and S 6  are distant from each other is in parallel with one side of the outer circumferential portion S 1 . 
         [0113]    A pair of through holes S 5  of one of the two wafer-side marks S 3  and S 4  are arranged to be shifted with respect to another pair of through holes S 6  in another direction along the surface of the wafer S and perpendicular to one direction. 
         [0114]    The shape of each of the through holes S 5  and S 6  in plan view is the same as the shape of each of the exposure openings  42   f  and  43   f  in plan view. 
         [0115]    In this embodiment, the shapes of the through holes S 5  and S 6  in plan view are asymmetrical in both directions of one direction and another direction. The shape of each of the through holes S 5  and S 6  is an L shape in which linear portions extending in one direction and another direction are connected to each other. 
         [0116]    The interval between a pair of through holes S 5  and S 6  differs between the two wafer-side marks S 3  and S 4  such that the wafer-side marks S 3  and S 4  have the same interval as the interval between the pairs of exposure openings  42   f  and  43   f  in the corresponding electrode film masks  42  and  43 . 
         [0117]    In this embodiment, the interval between a pair of through holes S 5  in the first wafer-side mark S 3  corresponding to the first mask  42  from the two wafer-side marks S 3  and S 4  is the same as the interval between a pair of exposure openings  42   f  of the first mask  42 . The interval between a pair of through holes S 6  of the second wafer-side mark S 4  corresponding to the second mask  43  from the two wafer-side marks S 3  and S 4  is the same as the interval between a pair of exposure openings  43   f  of the second mask  43 . 
         [0118]    At the same time the outline forming step is performed, a groove portion forming step of forming the groove portions  17  in a pair of vibrating arm portions  8  and  9  is performed (S 30 ), and thereafter, an electrode forming step of forming the electrode portion  18  in the wafer S in which the outline shape of the piezoelectric plate  11  is formed is performed (S 40 ). During this step, the electrode portion  18  (the excitation electrodes  14 , the extraction electrodes  19  and  20 , and the mount electrodes  15  and  16 ) and the weight metal films  21  are formed. 
         [0119]    Initially, as shown in  FIGS. 14 and 15 , a first metal film  28   a  serving as the base metal layer  18   a  and a second metal film  28   b  serving as the finish metal layer  18   b  are formed sequentially on the piezoelectric plate  11  by evaporation, sputtering, or the like to form a metal laminated film  28  (S 41 ). 
         [0120]    When the wafer S is formed of, for example, crystal and is transparent, it is difficult to confirm the shapes of the through holes S 5  and S 6 . Thus, as in this embodiment, if a metal film, such as the first metal film  28   a  or the second metal film  28   b,  is formed on the surface of the wafer S, it becomes easy to confirm the shapes of the through holes S 5  and S 6 . 
         [0121]    Next, a first electrode film forming step of forming the base metal layer  18   a  in the wafer S by a photolithography technique is performed using the first mask  42  (S 47 ). 
         [0122]    In the first electrode film forming step, first, a resist film  50  is applied to the wafer S, and the first mask  42  is arranged. Thereafter, a first resist pattern forming step of irradiating light through the first mask  42  to form a first resist pattern is performed (S 42 ). 
         [0123]    At this time, first, as shown in  FIG. 16 , a coating member  44  is arranged on the wafer S, and the resist film  50  is applied while the through holes S 5  of the first wafer-side mark S 3  are covered with the coating member  44 . Thus, as shown in  FIG. 17 , the resist film  50  is applied to a portion excluding the through holes S 5  and the peripheral portions of the through holes S 5 , and as shown in  FIG. 18 , the resist film  50  is applied, thereby suppressing unclearness of the shapes of the through holes S 5 . 
         [0124]    In this way, after the wafer S shown in  FIG. 19  is formed in which the metal laminated film  28  and the resist film  50  are laminated, the first mask  42  is arranged on the wafer S. At this time, the first mask  42  is arranged on the wafer S such that the mask-side mark  42   d  formed in the first mask  42  is aligned with the first wafer-side mark S 3 , and the through holes S 5  are exposed from the exposure openings  42   f.  Since the shapes of the through holes S 5  in plan view are the same as the shapes of the exposure openings  42   f  in plan view, at this time, the entire part of the through holes S 5  are exposed from the exposure openings  42   f.    
         [0125]    In this embodiment, when the first mask  42  is arranged on the wafer S such that the mask-side mark  42   d  is aligned with the first wafer-side mark S 3 , the coated portion  42   c  of the first mask  42  is configured to cover the regions where the mount electrodes  15  and  16 , the excitation electrodes  12  and  13 , the extraction electrodes  19  and  20 , and the weight metal films  21  are formed. After light is irradiated through the first mask  42 , if the first mask  42  is detached and the resist film  50  is developed, as shown in  FIG. 20 , a resist pattern which covers a portion where the metal laminated film  28  will remains, that is, the forming regions is formed. 
         [0126]    An etching step of etching the first metal film  28   a  and the second metal film  28   b  with the remaining resist film  50  as a mask is performed (S 43 ), and thereafter, the resist film  50  is removed. With this etching step, as shown in  FIGS. 21 and 22 , the first metal film  28   a  becomes the base metal layer  18   a  from the two metal films which constitute the electrode portion  18 . 
         [0127]    Next, a second electrode film forming step of forming the finish metal layer  18   b  in the wafer S by a photolithography technique is performed using the second mask  43  (S 48 ). The second electrode film forming step is performed by removing the second metal film  28   b  which is present in the single-layered region R (see  FIG. 4 ). 
         [0128]    During the second electrode film forming step, first, the resist film  50  is applied onto the wafer S, and the second mask  43  is arranged. Thereafter, a second resist pattern forming step of irradiating light through the second mask  43  to form a second resist pattern is performed (S 44 ). 
         [0129]    At this time, first, as shown in  FIG. 23 , the coating member  44  is arranged on the wafer S, and the resist film  50  is applied while the through holes S 6  of the second wafer-side mark S 4  are covered with the coating member  44 . Thus, as shown in  FIG. 24 , the resist film  50  is applied to a portion excluding the through holes S 6  and the peripheral portions of the through holes S 6 . 
         [0130]    Thereafter, the second mask  43  is arranged on the wafer S such that the mask-side mark  43   d  formed in the second mask  43  is aligned with the second wafer-side mark S 4 , and the through holes S 6  are exposed from the exposure openings  43   f.    
         [0131]    In this embodiment, when the second mask  43  is arranged on the wafer S such that the mask-side mark  43   d  is aligned with the second wafer-side mark S 4 , the coated portion  43   c  of the second mask  43  is configured to cover the laminated region P. Thus, after light is irradiated through the second mask  43 , if the second mask  43  is detached and the resist film  50  is developed, as shown in  FIG. 25 , a resist pattern which covers a portion where the second metal film  28   b  will remains, that is, the laminated region P is formed. 
         [0132]    An etching step of removing the second metal film  28   b  through etching with the remaining resist film  50  as a mask is performed (S 45 ), and thereafter, the resist film  50  is removed. With this etching step, as shown in  FIGS. 26 and 27 , the second metal film  28   b  becomes the finish metal layer  18   b  from the two metal layers which constitute the electrode portion  18 , and the electrode portion  18  and the weight metal films  21  are formed. Thus, the electrode forming step ends. 
         [0133]    Thereafter, in the single-layered region R with the finish metal layer  18   b  removed, the insulating film  34  made of an inorganic insulating material, such as SiO2, is formed on the base metal layer  18   a  through a metal mask (not shown) or the like by a CVD method or the like (S 46 ). When this happens, the insulating film  34  is formed to cover the base metal layer  18   a  of the single-layered region R. 
         [0134]    Thereafter, a rough adjustment step of roughly adjusting resonance frequency with respect to the entire part of the vibrating arm portions  8  and  9  formed in the wafer S is performed. This is, for example, a step of irradiating laser light onto the rough adjustment films  21   a  of the weight metal films  21  to reduce a weight applied to the front ends of a pair of vibrating arm portions  8  and  9 , thereby roughly adjusting frequency (S 51 ). 
         [0135]    Next, a cutting step of cutting connection portions which connect the wafer S and the piezoelectric vibrating pieces  2  and chipping a plurality of piezoelectric vibrating pieces  2  from the wafer S is performed (S 52 ). Thus, a plurality of piezoelectric vibrating pieces  2  in which the electrode portion  18  (the excitation electrodes  14 , the extraction electrodes  19  and  20 , and the mount electrodes  15  and  16 ) and the weight metal films  21  are formed can be manufactured from the wafer S at one time. 
         [0136]    As described above, according to the method of manufacturing a piezoelectric vibrating piece and the wafer of this embodiment, the interval between the pairs of through holes S 5  and S 6  differs between a plurality of wafer-side marks S 3  and S 4  such that the wafer-side marks S 3  and S 4  have the same interval as the interval between the pairs of exposure openings  42   f  and  43   f  in the corresponding electrode film masks  42  and  43 . During the resist pattern forming step, even when the exposure openings  42   f  and  43   f  of the electrode film masks  42  and  43  different from the electrode film masks  42  and  43  which should be originally used are aligned with the through holes S 5  and S 6  of the wafer-side marks S 3  and S 4  corresponding to the electrode film masks  42  and  43  which should be originally used, one of the pairs of exposure openings  42   f  and  43   f  is shifted from the through holes S 5  and S 6 . Therefore, it becomes possible to prevent a resist pattern from being formed in a state where different types of electrode film masks  42  and  43  are arranged and to suppress the disuse of the wafer S, thereby achieving low cost of the piezoelectric vibrating piece  2 . 
         [0137]    During the resist pattern forming step, the resist film  50  is applied while the through holes S 5  and S 6  are covered with the coating member  44 . For this reason, it is possible to suppress the unclearness of the shapes of the through holes S 5  and S 6  in plan view due to the application of the resist film  50 , and to reliably align the exposure openings  42   f  and  43   f  with the through holes S 5  and S 6 . 
         [0138]    During the resist pattern forming step, the through holes S 5  and S 6  are exposed from the exposure openings  42   f  and  43   f  to align the mask-side marks  42   d  and  43   d  with the wafer-side marks S 3  and S 4 , thereby reliably obtaining the above-described functional effects. 
         [0139]    The shapes of the exposure openings  42   f  and  43   f  in plan view are asymmetrical in both directions of one direction and another direction. For this reason, as shown in  FIG. 28 , during the resist pattern forming step, for example, even when the through holes S 5  are exposed from the exposure openings  42   f  in a state where the electrode film mask  42  is inversed in one direction with respect to the normal direction or is inversed in another direction, the entire part of the through holes S 5  cannot be exposed. Therefore, it is possible to prevent a resist pattern from being formed in a state where the electrode film masks  42  and  43  are arranged in different directions. 
         [0140]    The piezoelectric vibrator  1  of this embodiment includes the piezoelectric vibrating piece  2  manufactured by the method of manufacturing a piezoelectric vibrating piece, thereby achieving low cost. 
       (Oscillator) 
       [0141]    Next, an oscillator according to an embodiment of the invention will be described with reference to  FIG. 29 . 
         [0142]    As shown in  FIG. 29 , an oscillator  100  of this embodiment is configured as an oscillating element in which the piezoelectric vibrator  1  is electrically connected to an integrated circuit  101 . The oscillator  100  includes a substrate  103  on which an electronic component  102 , such as a capacitor, is mounted. The above-described integrated circuit  101  for an oscillator is mounted on the substrate  103 , and the piezoelectric vibrator  1  is mounted near the integrated circuit  101 . The electronic component  102 , the integrated circuit  101 , and the piezoelectric vibrator  1  are electrically connected to each other by wire patterns (not shown). The constituent components are molded with resin (not shown). 
         [0143]    In the oscillator  100  configured as above, if a voltage is applied to the piezoelectric vibrator  1 , the piezoelectric vibrating piece  2  in the piezoelectric vibrator  1  vibrates. The vibration is converted to an electrical signal by the piezoelectric characteristics of the piezoelectric vibrating piece  2 , and is input to the integrated circuit  101  as an electrical signal. The input electrical signal is subjected to various kinds of processing by the integrated circuit  101  and outputs as a frequency signal. Thus, the piezoelectric vibrator  1  functions as an oscillating element. 
         [0144]    The configuration of the integrated circuit  101 , for example, an RTC (real time clock) module or the like is selectively set in accordance with the requirements, thereby adding a function of controlling the operation date or time of the corresponding apparatus or an external apparatus or a function of providing time, calendar, or the like, in addition to a single-function oscillator for a timepiece or the like. 
         [0145]    As described above, since the oscillator  100  of this embodiment includes the low-cost and reliable piezoelectric vibrator  1 , with regard to the oscillator  100  itself, low cost can be achieved. It is also possible to obtain a stable and high-definition frequency signal over a long term. 
       (Electronic Apparatus) 
       [0146]    Next, an electronic apparatus according to an embodiment of the invention will be described with reference to  FIG. 30 . Description will be provided as to an example where a portable information apparatus  110  having the above-described piezoelectric vibrator  1  is used as an electronic apparatus. Initially, the portable information apparatus  110  of this embodiment is represented by, for example, a mobile phone, and is a developed and improved version of a wristwatch in the related art. The appearance is similar to a wristwatch, and a liquid crystal display is arranged in a portion corresponding to a dial plate, such that the current time or the like can be displayed on the screen. When an electronic apparatus is used as a communication tool, the user removes the electronic apparatus from the wrist and can perform communication as with a mobile phone in the related art using an internal speaker and a microphone inside a band. The size and weight are significantly reduced compared to a mobile phone in the related art. 
         [0147]    Next, the configuration of the portable information apparatus  110  of this embodiment will be described. As shown in  FIG. 30 , the portable information apparatus  110  includes the piezoelectric vibrator  1 , and a power supply unit  111  which supplies power. The power supply unit  111  is, for example, a lithium rechargeable battery. A control unit  112  which performs various kinds of control, a timepiece unit  113  which counts the time or the like, a communication unit  114  which performs communication with the outside, a display unit  115  which displays various kinds of information, and a voltage detection unit  116  which detects a voltage at each function unit are connected in parallel to the power supply unit  111 . Thus, power is supplied to the respective functional units by the power supply unit  111 . 
         [0148]    The control unit  112  controls the respective functional units to control the operations of the overall system, such as operations to transmit and receive sound data and operations to measure and display the current time. The control unit  112  includes a ROM in which a program is pre-installed, a CPU which reads and runs the program installed in the ROM, a RAM which is used as a work area of the CPU, and the like. 
         [0149]    The timepiece unit  113  includes an integrated circuit in which an oscillation circuit, a register circuit, a counter circuit, an interface circuit, and the like are integrated, and the piezoelectric vibrator  1 . When a voltage is applied to the piezoelectric vibrator  1 , the piezoelectric vibrating piece  2  vibrates, and the vibration is converted to an electrical signal by the piezoelectric characteristic of crystal and input to the oscillation circuit as an electrical signal. The output of the oscillation circuit is binarized and counted by the register circuit and the counter circuit. Transmission and reception of signals with respect to the control unit  112  are carried out through the interface circuit, and the current time, the current date, calendar information, or the like is displayed on the display unit  115 . 
         [0150]    The communication unit  114  has the same functions as a mobile phone in the related art, and includes a wireless unit  117 , a sound processing unit  118 , a switching unit  119 , an amplification unit  120 , a sound input/output unit  121 , a telephone number input unit  122 , an incoming call sound generation unit  123 , and a call control memory unit. 
         [0151]    The wireless unit  117  performs the transmission and reception of various kinds of data, such as sound data, with a base station through an antenna  125 . The sound processing unit  118  encodes and decodes a sound signal input from the wireless unit  117  or the amplification unit  120 . The amplification unit  120  amplifies a signal input from the sound processing unit  118  or the sound input/output unit  121  to a predetermined level. The sound input/output unit  121  has a speaker, a microphone, or the like, and makes incoming call sound or received sound loud or collects sound. 
         [0152]    The incoming call sound generation unit  123  generates incoming call sound in accordance with a call from a base station. The switching unit  119  switches the amplification unit  120  connected to the sound processing unit  118  to the incoming call sound generation unit  123  when a call is received, such that incoming call sound generated by the incoming call sound generation unit  123  is output to the sound input/output unit  121  through the amplification unit  120 . 
         [0153]    The call control memory unit  124  stores a program relating to incoming/outgoing call control in communication. The telephone number input unit  122  includes, for example, numeric keys from 0 to 9 and other keys. The user depresses the numeral keys and the like to input the telephone number of call destination or the like. 
         [0154]    When a voltage applied to each functional unit, such as the control unit  112 , by the power supply unit  111  falls below a predetermined value, the voltage detection unit  116  detects the voltage drop and notifies the voltage drop to the control unit  112 . The predetermined voltage value at this time is a value which is set in advance as a minimum voltage necessary for stably operating the communication unit  114 , and is set to, for example, about 3 V. When receiving the notification of the voltage drop from the voltage detection unit  116 , the control unit  112  prohibits the operations of the wireless unit  117 , the sound processing unit  118 , the switching unit  119 , and the incoming call sound generation unit  123 . In particular, it is inevitably necessary to stop the operation of the wireless unit  117  which consumes large power. A message that a remaining battery quantity is short and the communication unit  114  is inoperable is also displayed on the display unit  115 . 
         [0155]    That is, the operation of the communication unit  114  can be prohibited by the voltage detection unit  116  and the control unit  112 , and a message that the operation of the communication unit  114  is prohibited can be displayed on the display unit  115 . This display may be a text message, and as more intuitive display, a × (cross) mark may be attached to a telephone icon displayed at an upper part of the display screen of the display unit  115 . 
         [0156]    A power shutoff unit  126  is provided to selectively shut off power of a portion relating to the function of the communication unit  114 , thereby more reliably stopping the function of the communication unit  114 . 
         [0157]    As described above, since the portable information apparatus  110  of this embodiment includes the low-cost and reliable piezoelectric vibrator  1 , with regard to the portable information apparatus itself, it is possible to achieve low cost. It is also possible to display stable and high-definition timepiece information over a long term. 
       (Radio-Controlled Timepiece) 
       [0158]    Next, a radio-controlled timepiece according to an embodiment of the invention will be described with reference to  FIG. 31 . 
         [0159]    As shown in  FIG. 31 , a radio-controlled timepiece  130  of this embodiment is a timepiece which includes the piezoelectric vibrator  1  which is electrically connected to a filter unit  131 , and has a function of receiving a standard electric wave including timepiece information, automatically correcting a time to an accurate time, and displaying the corrected time. 
         [0160]    In Japan, transmission installations (transmission stations) which transmit the standard electric waves are located in the Fukushima prefecture (40 kHz) and the Saga prefecture (60 kHz) and transmit the standard electric waves. A long wave having a frequency of 40 kHz or 60 kHz has both of property that the wave propagates on the ground and property that the wave propagates while being reflected between an ionosphere and the ground. Hence, a propagation range is wide, such that the standard electric waves can cover all areas of Japan with the above-described two transmission installations. 
         [0161]    Hereinafter, the functional configuration of the radio-controlled timepiece  130  will be described in detail. 
         [0162]    The antenna  132  receives the standard electric wave of a long wave having a frequency of 40 kHz or 60 kHz. The standard electric wave of a long wave is an electric wave which is obtained through AM modulation of time information called as a time code on a carrier wave having a frequency of 40 kHz or 60 kHz. The received standard electric wave of a long wave is amplified by an amplifier  133 , is filtered by a filter unit  131  having a plurality of piezoelectric vibrators  1 , and is tuned. 
         [0163]    The piezoelectric vibrators  1  of this embodiment respectively include crystal vibrator portions (piezoelectric vibrating pieces)  138  and  139  having resonance frequency of 40 kHz and 60 kHz as same as the above-described frequency of the carrier wave. 
         [0164]    A filtered signal having a predetermined frequency is detected and demodulated by a detection and rectification circuit  134 . Subsequently, the time code is extracted through a waveform shaping circuit  135  and is counted by a CPU  136 . The CPU  136  reads information on current year, cumulative days, day of week, time, and the like. The read information is reflected on an RTC  137  such that accurate time information is displayed. 
         [0165]    The carrier wave has a frequency of 40 kHz or 60 kHz, thus the crystal vibrator portions  138  and  139  preferably have a vibrator having the above-described tuning-fork structure. 
         [0166]    Although the above description has been provided as to the radio-controlled timepiece used in Japan, the frequency of the standard electric wave of long wave overseas is different from the standard electric wave in Japan. For example, the standard electric wave having a frequency of 77.5 kHz is used in Germany. Accordingly, in incorporating the radio-controlled timepiece  130  compatible with the oversea use into a portable apparatus, the piezoelectric vibrator  1  having a frequency different from the frequency used in Japan is required. 
         [0167]    As described above, since the radio-controlled timepiece  130  of this embodiment includes the low-cost and reliable piezoelectric vibrator  1 , with regard to the radio-controlled timepiece itself, it is possible to achieve low cost. It is also possible to count a time stably with high definition over a long term. 
         [0168]    The technical scope of the invention is not limited to the above-described embodiment, and various modifications may be made without departing from the gist of the invention. 
         [0169]    For example, although in the above-described embodiment, the cylinder package type piezoelectric vibrator  1  has been described as an example of a piezoelectric vibrator, the invention is not limited thereto. For example, a surface-mounted piezoelectric vibrator, a ceramic package type piezoelectric vibrator, or a cylinder package type piezoelectric vibrator  1  may be solidified in a mold resin portion to form a surface-mounted vibrator. 
         [0170]    The invention is not limited to the tuning fork type piezoelectric vibrating piece  2  and may be applied to an AT piezoelectric vibrating piece. 
         [0171]    The electrode portion  18  is not limited to that in the above-described embodiment insofar as an electrode portion has a plurality of electrode films which are laminated on the outer surface of the piezoelectric plate  11  and have different patterns. For example, three or more electrode films may be laminated. 
         [0172]    Although in the above-described embodiment, a positive type is used as the resist film  50 , a negative type may be used. 
         [0173]    Although in the above-described embodiment, the two wafer-side masks S 3  and S 4  corresponding to the two electrode film masks  42  and  43  are formed in the wafer S simultaneously with the outline shape of the piezoelectric plate  11 , the invention is not limited thereto. 
         [0174]    Although in the above-described embodiment, the wafer-side marks S 3  and S 4  are the through holes S 5  and S 6 , the wafer-side marks S 3  and S 4  may be concave portions which do not pass through the wafer S. 
         [0175]    Although in the above-described embodiment, during the resist pattern forming step, the coating member  44  is arranged on the wafer S, and the resist film  50  is applied while the peripheral portions of the through holes S 5  and S 6  of the wafer-side marks S 3  and S 4  corresponding to the electrode film masks  42  and  43  are covered with the coating member  44 , the peripheral portions of the through holes S 5  and S 6  may not be covered with the coating member  44 . 
         [0176]    The shapes of the exposure openings  42   f  and  43   f  of the first mask  42  and the second mask  43  in plan view and the through holes S 5  and S 6  of the wafer S are not limited to the above-described embodiment insofar as the shapes of the exposure openings  42   f  and  43   f  of the first mask  42  and the second mask  43  in plan view and the through holes S 5  and S 6  of the wafer S are asymmetrical in both directions of one direction and another direction. The shapes in plan view shown in  FIGS. 32 to 35  may be used. 
         [0177]    For example, as shown in  FIG. 32 , the shape of an exposure openings  45 A (through hole S 11 ) in plan view may be pentagonal asymmetrical in both directions of one direction and another direction. The shape in plan view is a shape in which one corner portion of a square (rectangle) extending in both directions of one direction and another direction is chamfered. 
         [0178]    For example, as shown in  FIGS. 33 to 35 , exposure openings  45 B,  45 C, and  45 D (through holes S 12 , S 13 , and S 14 ) may have a plurality of discontinuous portions. 
         [0179]    The exposure openings  45 B and  45 C (through holes S 12  and S 13 ) shown in  FIGS. 33 and 34  include a first portion  45   a  having an L shape in which linear portions extending in one direction and another direction are connected to each other, and a second portion  45   b  which is arranged to face the respective unconnected portions of the linear portions of the first portion  45   a  in both directions of one direction and another direction. The shape of the second portion  45   b  in plan view is a square (rectangle) extending in both directions of one direction and another direction. In the exposure opening  45 B (through hole S 12 ) shown in  FIG. 33 , the second portion  45   b  has a size to be located inward in one direction of the first portion  45   a  and inward in another direction. In the exposure opening  45 C (through hole S 13 ) shown in  FIG. 34 , the second portion  45   b  has a size to protrude outward in one direction and to protrude outward in another direction with respect to the first portion  45   a.    
         [0180]    The exposure opening  45 D (through hole S 14 ) shown in  FIG. 35  includes a first portion  45   a  and a second portion  45   b  which have in a circular shape in plan view and are different in size. 
         [0181]    Although in the above-described embodiment, the shapes of the exposure openings (through holes) in plan view are asymmetrical in both directions of one direction and another direction, the exposure openings (through holes) may not be asymmetrical. 
         [0182]    Although in the above-described embodiment, during the resist pattern forming step, the electrode film masks  42  and  43  are arranged in the wafer S such that the through holes S 5  and S 6  are exposed from the exposure openings  42   f  and  43   f,  the invention is not limited thereto. 
         [0183]    For example, instead of forming the exposure openings as the mark portions in the electrode film masks, the width of the electrode film mask may differ between a plurality of electrode film masks, and during the resist pattern forming step, both end portions of the electrode film mask as a mark portion may be aligned with the through holes. 
         [0184]    The constituent elements of the above-described embodiment can be suitably replaced with well-known constituent elements without departing from the gist of the invention, and the above-described modifications may be suitably combined with each other.