Patent Publication Number: US-2015084160-A1

Title: Semiconductor device and method of manufacturing the same

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application is a divisional of application Ser. No. 13/301,396, filed Nov. 21, 2011, which is based upon and claims the benefit of priority of the prior Japanese Patent Application No. 2011-009063, filed on Jan. 19, 2011, the entire contents of which are incorporated herein by reference. 
    
    
     FIELD 
     The embodiments discussed herein relate to a semiconductor device including a ferroelectric capacitor, and a method of manufacturing the semiconductor device. 
     BACKGROUND 
     With the recent developments in digital technologies, size reduction, performance enhancement, and multifunctionalization of various electronic devices have been advanced. Many of these electronic devices use semiconductor devices (LSI: Large Scale Integration) having built-in storage elements. The storage elements include volatile memory which loses data when power supply stops, and non-volatile memory which can retain data without power supply. 
     The volatile memory includes DRAM (Dynamic Random-Access Memory), SRAM (Static Random Access Memory), and the like, and has an advantage of allowing high-speed data access. Meanwhile, the non-volatile memory includes EEPROM (Electrically Erasable Programmable Read Only Memory), flash memory, FeRAM (Ferroelectric Random Access Memory), and the like. The above-described semiconductor devices are provided with either or both of the volatile memory and the non-volatile memory, depending on the purposes of use of the semiconductor devices. 
     FeRAM, which is a kind of non-volatile memory, has advantages of allowing fast-speed data access, consuming low power, and allowing high-frequency rewriting. FeRAM uses ferroelectric capacitors to store data. The ferroelectric capacitors each have a structure in which a film made of a ferroelectric material having a ferroelectric characteristic (spontaneous polarization), such as PZT (PbZr x Ti 1-x O 3 , provided that 0&lt;x&lt;1), is sandwiched between a pair of electrodes.
     [Patent Document 1] International Patent Pamphlet No. WO 2004053991   [Patent Document 2] Japanese Laid-open Patent Publication No. 2008-071825   [Patent Document 3] Japanese Laid-open Patent Publication No. 2006-318941   

     Semiconductor devices are preferably more miniaturized and more power-saving. To meet these demands, FeRAM preferably has a ferroelectric film having a reduced film thickness. 
     SUMMARY 
     One aspect of a technology disclosed herein provides a semiconductor device including: a semiconductor substrate; a capacitor formed above the semiconductor substrate, and having a lower electrode, a ferroelectric film, and an upper electrode; and a conductive oxide film provided between the ferroelectric film and the upper electrode, and having the same structure as a structure of the ferroelectric film, and containing a ferroelectric material provided with conductivity. 
     Meanwhile, another aspect of the technology disclosed herein provides a method of manufacturing a semiconductor device, the method comprising: forming a lower electrode film above a semiconductor substrate; forming a dielectric film made of a ferroelectric material on the lower electrode film; subjecting the dielectric film to a crystallization treatment; and forming a conductive oxide film on the dielectric film, the conductive oxide film being made of a ferroelectric material to which conductivity is provided by adding a conductive material. 
     The object and advantages of the invention will be realized and attained by means of the elements and combinations particularly pointed out in the claims. 
     It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory and are not restrictive of the invention, as claimed. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1A  is a cross-sectional view illustrating an example of a ferroelectric capacitor, and  FIG. 1B  is a diagram schematically illustrating a structure of layers of the same ferroelectric capacitor; 
         FIG. 2  is a graph illustrating the relationship between the switching charge Qsw and the applied voltage V of dielectric films having various film thicknesses in ferroelectric capacitors having the structure of  FIGS. 1A and 1B ; 
         FIG. 3  is a diagram illustrating an example of the relationship between the film thickness and the saturation charge Qt of the dielectric films in the ferroelectric capacitors having the structure of  FIGS. 1A and 1B ; 
         FIG. 4  is a diagram illustrating an example of the relationship between the film thickness and the V50 of the dielectric films in the ferroelectric capacitors having the structure of  FIGS. 1A and 1B ; 
         FIG. 5A  is a cross-sectional view illustrating another example of a ferroelectric capacitor, and  FIG. 5B  is a diagram schematically illustrating the structure of layers in the same ferroelectric capacitor; 
         FIG. 6  is a graph illustrating the relationship between the switching charge Qsw and the applied voltage V of dielectric films having various film thicknesses in ferroelectric capacitors having the structure of  FIGS. 5A and 5B ; 
         FIG. 7  is a diagram illustrating an example of the relationship between the film thickness and the saturation charge Qt of the dielectric films in the ferroelectric capacitors having the structure of  FIGS. 5A and 5B ; 
         FIG. 8  is a diagram illustrating an example of the relationship between the film thickness and the V50 of the dielectric films in the ferroelectric capacitors having the structure of  FIGS. 5A and 5B ; 
         FIG. 9  is a cross-sectional view illustrating the structure of a semiconductor device according to a first embodiment; 
         FIGS. 10A to 10U  are cross-sectional views illustrating a method of manufacturing a semiconductor device according to the first embodiment; 
         FIG. 11A  is a cross-sectional view illustrating a ferroelectric capacitor of the first embodiment, and  FIG. 11B  is a diagram schematically illustrating a layer structure of the same ferroelectric capacitor; 
         FIG. 12A  is a diagram illustrating an example of results obtained by investigating the Ir concentration distribution in a ferroelectric capacitor of Example,  FIG. 12B  is a diagram illustrating an example of results obtained by investigating the Ir concentration distribution in ferroelectric capacitors of Comparative Examples 1 and 2; 
         FIG. 13  is a diagram illustrating an example of results obtained by investigating the Ir percentage content and the resistivity; 
         FIG. 14  is a graph illustrating an example of the relationship between the switching charge Qsw and the applied voltage V (Qtv characteristics) of ferroelectric capacitors of Examples with various film thicknesses; 
         FIG. 15  is a diagram illustrating an example of the saturation charge Qt of each of the ferroelectric capacitors in  FIG. 14 ; 
         FIG. 16  is a diagram illustrating an example of the V50 of each of the ferroelectric capacitors in  FIG. 14 ; 
         FIG. 17  is a diagram illustrating an example of the relationship between the switching charge Qsw and the applied voltage V (Qtv characteristics) of ferroelectric capacitors of Examples having conductive oxide films with various film thicknesses; 
         FIG. 18  is a diagram illustrating an example of the saturation charge Qt of each of the ferroelectric capacitors in  FIG. 17 ; 
         FIG. 19  is a diagram illustrating an example of the V50 of each of the ferroelectric capacitors in  FIG. 17 ; 
         FIG. 20  is a graph illustrating an example of the relationship between the switching charge Qsw and the applied voltage V (Qtv characteristics) of ferroelectric capacitors of Examples having dielectric films with various film thicknesses; 
         FIG. 21  is a diagram illustrating an example of the saturation charge Qt of each of the ferroelectric capacitors in  FIG. 20 ; 
         FIG. 22  is a diagram illustrating an example of the V50 of each of the ferroelectric capacitors in  FIG. 20 ; 
         FIG. 23  is a graph illustrating an example of results obtained when ferroelectric capacitors of Example and Comparative Examples are subjected to a stress test; 
         FIG. 24  is a diagram illustrating an example of the fatigue loss of the ferroelectric capacitors of Example and Comparative Examples; and 
         FIG. 25  is a view for describing a semiconductor device according to a second embodiment, and a method of manufacturing the semiconductor device. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     Hereinafter, prelude for facilitating the understanding of embodiments will be described prior to the description of the embodiments. 
       FIG. 1A  is a cross-sectional view illustrating an example of a ferroelectric capacitor, and  FIG. 1B  is a diagram schematically illustrating a structure of layers of the same ferroelectric capacitor. 
     The ferroelectric capacitor  210  illustrated in  FIGS. 1A and 1B  has a structure in which a lower electrode film  211 , a dielectric film  212 , a first upper electrode film  213 , and a second upper electrode film  214  are stacked in this order from the bottom. The lower electrode film  211  is formed of Pt (platinum). The dielectric film  212  is formed of PZT. The first upper electrode film  213  is formed of IrOx (iridium oxide: provided that 0&lt;x). The second upper electrode film  214  is formed of IrO 2  (iridium oxide). As illustrated in  FIG. 1B , the dielectric film  212  has a columnar crystal structure, and each of the lower electrode film  211  and the upper electrode films  213  and  214  has a crystallized structure. 
     The electrode films  213  and  214  are formed on the dielectric film  212  by a sputtering method or the like. At this time, the dielectric film  212  is damaged, and the ferroelectric characteristics thereof deteriorate. Moreover, also when the electrode films  211 ,  213 , and  214  and the dielectric film  212  are patterned, the dielectric film  212  is damaged. For this reason, after a film formation process for forming the electrode films  213  and  214 , or a patterning process, a heat treatment (annealing) is performed in an oxygen atmosphere to thereby recover the damage on the dielectric film  212 , in general. 
     However, interdiffusion occurs between Ir (iridium) in the electrode films  213  and  214  and Pb (lead) in the dielectric film  212  during the heat treatment. As a result, a paraelectric layer (dead layer)  218  is formed at an interface between the dielectric film  212  and the electrode film  213 . Since a voltage applied to the dielectric film  212  is reduced by an amount corresponding to the paraelectric layer  218 , the operating voltage of the ferroelectric capacitor  210  is increased. 
     In general, characteristics of a ferroelectric capacitor are evaluated on the basis of the relationship between the switching charge Qsw and the applied voltage V (hereinafter referred to as Qtv characteristics). However, the Qtv characteristics are influenced by the leak current of the capacitor. For evaluation of the true capacitor characteristics which are not influenced by the leak current, it is preferably to determine the saturation charge Qt and the coercive electric field (or coercive voltage) of the capacitor from the Qtv characteristics by use of a mathematical model. 
     The saturation charge Qt represents not simply the magnitude of the switching charge Qsw, but represents a charge which actually contributes to the polarization switching. For this reason, the saturation charge Qt is an important parameter in developing a material for a ferroelectric capacitor driven at a low voltage. 
       FIG. 2  is a graph illustrating an example of the relationship between the switching charge Qsw and the applied voltage V in the cases where the film thicknesses of the dielectric film  212  are 100 nm, 120 nm, 130 nm, and 150 nm, respectively. In  FIG. 2 , the horizontal axis represents the applied voltage, and the vertical axis represents the switching charge Qsw.  FIG. 3  is a diagram illustrating an example of the relationship between the film thickness of the dielectric film  212  and the saturation charge Qt.  FIG. 4  is a diagram illustrating an example of the relationship between the film thickness of the dielectric film  212  and the V50. Note that the V50 is a voltage at which 50% of the domains in the dielectric film  212  are polarized and rearranged by an applied electric field in the direction of the electric field. The value of V50 has a relationship with the coercive voltage Vc, and it may be said that a smaller value of V50 allows operation at a lower voltage. 
     As seen from  FIGS. 2 and 4 , as the film thickness of the dielectric film  212  becomes thinner, the curve (Qtv characteristics) representing the relationship between the switching charge Qsw and the applied voltage V rises at an earlier stage, and the V50 also becomes lower, in the case of the ferroelectric capacitor  210  of  FIGS. 1A and 1B . However, the degree of the reduction in V50 is small relative to the decrease in the film thickness. 
     Moreover, as seen from  FIG. 3 , as the film thickness of the dielectric film  212  becomes thinner, the saturation charge Qt becomes lower. This means that when the film thickness of the dielectric film  212  is reduced to meet the demands for higher integration and lower driving voltage of a semiconductor device, the characteristics of the ferroelectric capacitor  210  change. In the ferroelectric capacitor  210  of this structure, the dielectric film  212  preferably has a film thickness of 130 nm or more. If the film thickness is less than 130 nm, the saturation charge Qt becomes so small that it becomes difficult to obtain desired characteristics. 
       FIG. 5A  is a cross-sectional view illustrating another example of the ferroelectric capacitor.  FIG. 5B  is a diagram schematically illustrating the structure of layers of the same ferroelectric capacitor. 
     The ferroelectric capacitor  220  illustrated in  FIGS. 5A and 5B  has a structure in which a lower electrode film  221 , a first dielectric film  222 , a second dielectric film  223 , a first upper electrode film  224 , and a second upper electrode film  225  are stacked in this order from the bottom. The lower electrode film  221  is formed of Pt. The first dielectric film  222  and the second dielectric film  223  are formed of PZT. The first upper electrode film  224  is formed of IrOx. The second upper electrode film  225  is formed of IrO 2 . Note that the reference numeral  228  in  FIG. 5B  represents a paraelectric layer formed because of interdiffusion of Ir and Pb between the dielectric films  222  and  223  and the electrode films  224  and  225 . 
       FIG. 6  is a graph illustrating an example of the relationship between the switching charge Qsw and the applied voltage V. In the  FIG. 6 , the horizontal axis represents the applied voltage, and the vertical axis represents the switching charge Qsw. Meanwhile,  FIG. 7  is a diagram illustrating an example of the relationship between the film thickness of the dielectric film (the total film thickness of the dielectric film  212  and the dielectric film  222 ) and the saturation charge Qt.  FIG. 8  is diagram illustrating an example of the relationship between the film thickness of the dielectric film (the total film thickness of the dielectric film  221  and the dielectric film  222 ) and the V50. 
     As seen from  FIGS. 6 and 8 , as the film thickness of the ferroelectric capacitor  220  of  FIGS. 5A and 5B  becomes thinner, the curve (Qtv characteristics) representing the relationship between the switching charge Qsw and the applied voltage V rises at an earlier stage, and the V50 also becomes lower. As seen from  FIG. 7 , as the film thickness of the dielectric film (the total film thickness of the first dielectric film  221  and the second dielectric film  222 ) becomes thinner, the saturation charge Qt becomes lower, in the case of the ferroelectric capacitor  220  having the structure illustrated in  FIGS. 5A and 5B . 
     The ferroelectric capacitor  220  in  FIGS. 5A and 5B  has a smaller leak current and a thinner layer thickness of the paraelectric layer than the ferroelectric capacitor  210  in  FIGS. 1A and 1B . However, also in the case of the ferroelectric capacitor  220 , the film thickness of the dielectric film (the total film thickness of the first dielectric film  221  and the second dielectric film  222 ) is preferably 100 nm or more. If the film thickness is thinner than 100 nm, the saturation charge Qt becomes so low that it becomes difficult to obtain desired characteristics. 
     Hereinafter, embodiments will be described. 
     First Embodiment 
       FIG. 9  is a cross-sectional view illustrating a structure of a semiconductor device according to a first embodiment. In the description of the first embodiment, a planar-type FeRAM is taken as an example. 
     An element isolation film  12  is formed in a predetermined region of a semiconductor substrate (a silicon substrate)  10 . Moreover, wells  14  are formed in element formation regions defined by the element isolation film  12 . 
     A pair of source and drain regions  22  separated from each other are formed in each well  14  in a memory cell formation region. Moreover, a gate electrode  18  is formed on a region between the source and drain regions  22  with a gate insulating film  16  interposed therebetween. A transistor  26  of a memory cell is formed which includes the source and drain regions  22  and the gate electrode  18 . Note that a silicide film  24   a  is formed on the gate electrode  18 , and a silicide film  24   b  is formed on each of the surfaces of the source and drain regions  22 . Moreover, side walls  20  are formed on both sides of the gate electrode  18 , respectively. 
     The transistor  26  is covered with an insulating film  28 . An interlayer insulating film  30  is formed on the insulating film  28 . A conductive plug  36  is embedded in the interlayer insulating film  30  and the insulating film  28 . The conductive plug  36  is a high-melting-point metal such as W (tungsten) filled into a contact hole  32  which extends from the top surface of the interlayer insulating film  30  to the silicide film  24   b . A wall surface of the contact hole  32  is covered with an adhesion layer  34 , which secures the adhesion between the conductive plug  36  and the silicide film  24   b.    
     An interlayer insulating film  42  is formed on the interlayer insulating film  30 . In the first embodiment, the interlayer insulating film  42  has a structure in which a SiN film  38  and SiO 2  film  40  are stacked on each other. 
     A ferroelectric capacitor  62  is formed on a predetermined region of the interlayer insulating film  42  with an adhesion layer  43  interposed therebetween. The ferroelectric capacitor  62  has a structure in which a lower electrode  48 , a dielectric film  50 , and an upper electrode  60  are stacked in this order from the bottom. The dielectric film  50  is formed of an oxide having ferroelectric characteristics. Examples of the oxide having ferroelectric characteristics include oxides each having a perovskite structure such as PZT, PLZT, and CSPLZT, and oxides each having a bismuth layered crystal structure, such as BST, BLT, and BFO. These oxides are represented by a chemical formula ABOx (provided that A and B are metal elements, and 0&lt;x). 
     The lower electrode  48  has a structure in which a conductive film  44  and a noble metal film  46  are staked on each other. The upper electrode  60  has a structure in which a conductive oxide film  52 , a conductive film  56 , and a conductive film  58  are stacked in this order form the bottom. Of these films, the conductive oxide film  52  is formed of a material to which conductivity is provided by adding a metal element (conductive material) such as Ir (iridium) or Ru (ruthenium) to a ferroelectric material. 
     The ferroelectric capacitor  62  is covered with a protection film  64 . A protection film  66  is formed on the interlayer insulating film  42  and the protection film  64 . These protection films  64  and  66  prevent entry of hydrogen and water, which cause deterioration in characteristics of the ferroelectric capacitor  62 . 
     An interlayer insulating film  68  is formed on the protection film  66 . A protection film  70  is formed on the interlayer insulating film  68 . In addition, an interlayer insulating film  72  is formed on the protection film  70 , and wirings  90  are formed in a predetermined pattern on the interlayer insulating film  72 . In the first embodiment, each of the wirings  90  has a structure in which a TiN film  82 , an AlCu alloy film  84 , a Ti film  86 , and a TiN film  88  are stacked on each other. 
     The lower electrode  48  of the ferroelectric capacitor  62  is electrically connected to a predetermined wiring  90  through a conductive plug  80   a . The upper electrode  60  is electrically connected to another wiring  90  through a conductive plug  80   b . Meanwhile, each of the source and drain regions  22  of the transistor  26  is electrically connected to still another wiring  90  through the silicide film  24   b , the conductive plug  36 , and a conductive plug  80   c.    
     The conductive plugs  80   a ,  80   b , and  80   c  are formed by filling a high-melting-point metal such as W (tungsten) into the contact holes  74   a ,  74   b , and  76  provided in the interlayer insulating film  72 , the protection film  70 , and the interlayer insulating film  68 , respectively. An adhesion layer  78  is formed between the high-melting-point metal and the wall surface of each of the contact holes  74   a ,  74   b , and  76 . 
     The semiconductor device of the first embodiment has the conductive oxide film  52  on the dielectric film  50  as described above. The conductive oxide film  52  is formed of a material to which conductivity is provided by adding a metal element such as Ir or Ru to a ferroelectric material. This suppresses the formation of the paraelectric layer due to the interdiffusion between the dielectric film  50  and the upper electrode  60  as described later. This, in turn, may allow a low-voltage operation, and enable favorable ferroelectric characteristics to be obtained even when the thickness of the dielectric film  50  is reduced. 
     Hereinafter, a method of manufacturing a semiconductor device according to the first embodiment will be described. 
       FIGS. 10A to 10U  are cross-sectional views sequentially illustrating steps of the method of manufacturing a semiconductor device according to the first embodiment. 
     First, a step of obtaining the structure in  FIG. 10A  is described. First, a semiconductor substrate (silicon substrate)  10  is prepared, and an element isolation film  12  is formed in the semiconductor substrate  10  by a known STI (Shallow Trench Isolation) method, a LOCOS (Local Oxidation of Silicon) method, or the like. Each region surrounded by the element isolation film  12  serves as an element formation region in which an element such as a transistor is to be formed. 
     Thereafter, impurities are introduced into the element formation region of the semiconductor substrate  10  by, for example, an ion implantation method. Thus, a well  14  is formed. Here, p-type impurities such as B (boron) are introduced into an n-type transistor formation region to form a p well, whereas n-type impurities such as P (phosphorus) are introduced into a p-type transistor formation region to form a n well. 
     Next, the surface of the well  14  is thermally oxidized to form a gate insulating film  16 . The gate insulating film  16  has a thickness of, for example, 6 nm to 7 nm. Thereafter, a polysilicon film having, for example, a thickness of 180 nm is formed on the entire top surface of the semiconductor substrate  10  by, for example, a CVD (Chemical Vapor Deposition) method. Then, the polysilicon film is patterned to form a gate electrode  18  by use of a photolithography method and an etching method. Note that the gate electrode  18  of the transistor  26 , which is to be connected to the ferroelectric capacitor  62  to constitute a memory cell, serves as a word line. 
     Next, impurities are introduced shallowly into the well  14  at a low concentration by an ion implantation method or the like using the gate electrode  18  as a mask. Thus, a low concentration impurity region to serve as an extension is formed. In this case, n-type impurities such as P (phosphorus) or As (arsenic) are introduced into an n-type transistor formation region, whereas p-type impurities such as B (boron) are introduced into a p-type transistor formation region. 
     Next, sidewalls  20  are formed on both sides of the gate electrode  18 , respectively. The sidewalls  20  may be formed by first forming an insulating film of SiO 2  (silicon oxide), SiN (silicon nitride), or the like having a thickness of about 300 nm on the entire top surface of the semiconductor substrate  10  by, for example, a CVD method, and then anisotropically etching the insulating film. 
     After that, impurities are ion implanted into the well  14  at a high concentration by use of the gate electrode and the sidewalls  20  as a mask. Thus, a high-concentration impurity region is formed. In this case, n-type impurities such as P (phosphorus) or As (arsenic) are introduced into a well in an n-type transistor formation region, whereas p-type impurities such as B (boron) are introduced into a well in a p-type transistor formation region. Each of the source and drain regions  22  having the low-concentration impurity region (extension) and the high-concentration impurity region is thus formed. 
     Next, a high-melting-point metal film made of a high-melting-point metal such as Co (cobalt) is formed on the entire top surface of the semiconductor substrate  10  by, for example, a sputtering method. Then, a heat treatment is conducted at a predetermined temperature. The heat treatment causes silicon and the high-melting-point metal to react with each other at the interface between the high-melting-point metal film and the gate electrode  18  and at the interfaces between the high-melting-point metal film and the source and drain regions  22 . As a result, a silicide is formed. Thereafter, the unreacted high-melting-point metal is removed by wet-etching or the like. Thus, a silicide film  24   a  is formed on the surface of the gate electrode  18 , and a silicide film  24   b  is formed on the surface of each of the source and drain regions  22 . 
     Next, a step of obtaining the structure in  FIG. 10B  is described. After the formation of the silicide films  24   a  and  24   b  in the above-described step, SiON (silicon oxynitride) is deposited on the entire top surface of the semiconductor substrate  10  in a thickness of approximately 200 nm by, for example, a plasma CVD method. Thus, an insulating film  28  is formed. Thereafter, SiO 2  is deposited on the insulating film  28  in a thickness of approximately 1 μm by, for example, a plasma CVD method using TEOS (Tetra Ethoxy Silane) gas. Thus, an interlayer insulating film  30  is formed. Subsequently, the interlayer insulating film  30  is polished to make a surface thereof flat by, for example, a CMP (Chemical Mechanical Polishing) method. The height from the top surface of the semiconductor substrate  10  (the well  14 ) to the top surface of the interlayer insulating film  30  is, for example, about 785 nm after the CMP. 
     Next, a step of obtaining the structure in  FIG. 10C  is described. After the formation of the interlayer insulating film  30  in the above-described step, a contact hole  32  is formed by conducting a photolithography process and an etching process. The contact hole  32  extends from the top surface of the interlayer insulating film  30  to the silicide film  24   b . The contact hole  32  has a diameter of, for example, 0.25 μm. 
     Next, a step of obtaining the structure of  FIG. 10D  is described. After the formation of the contact hole  32  in the above-described step, a Ti (titanium) film having a thickness of 30 nm is formed on the entire top surface of the semiconductor substrate  10  by, for example, a sputtering method. Further, a TiN (titanium nitride) film having a thickness of 20 nm is formed on the Ti film. Thus, an adhesion layer  34  having a layered structure of the Ti film and the TiN film is obtained. The surface in the contact hole  32  is covered with the adhesion layer  34 . 
     Next, a conductive material such as W (tungsten) is deposited on the entire top surface of the semiconductor substrate  10  by, for example, a CVD method. Thus, the contact hole  32  is filled with the conductive material. Thereafter, the conductive material and the adhesion layer  34  on the interlayer insulating film  30  are removed by, for example, a CMP method to an extent that the interlayer insulating film  30  is exposed. The conductive material left in the contact hole  32  is to be a conductive plug  36 . 
     Next, a step of obtaining the structure in  FIG. 10E  is described. After the formation of the conductive plug  36  in the above-described step, a SiN film  38  having a thickness of approximately 100 nm is formed on the entire top surface of the semiconductor substrate  10  by, for example, a plasma CVD method. Thereafter, a SiO 2  film  40  having a thickness of approximately 130 nm is formed on the SiN film  38  by, for example, a plasma TEOS CVD method. An interlayer insulating film  42  is formed by the SiN film  38  and the SiO 2  film  40 . The interlayer insulating film  42  is intended to prevent oxidation of the conductive plug  36 . The interlayer insulating film  42  may be formed of an insulating material such as SiN or Al 2 O 3  (aluminum oxide). 
     Next, gas contained in the interlayer insulating film  42  is released from the interlayer insulating film  42  by a heat treatment, for example, in a nitrogen atmosphere at a temperature of 650° C. for 30 minutes. Thereafter, an Al 2 O 3  film having a thickness of 20 nm is formed on the interlayer insulating film  42  by, for example, a sputtering method. Thus, an adhesion layer  43  is formed. The adhesion layer  43  is intended to secure the adhesion of a conductive film  44  to be formed next. 
     Next, a step of obtaining the structure in  FIG. 10F  is described. After the formation of the adhesion layer  43  in the above-described step, a conductive film  44  having a thickness of 50 nm to 150 nm is formed on the adhesion layer  43  by, for example, a sputtering method. Here, a Pt (platinum) film is formed as the conductive film  44 . Film formation conditions for formation of the Pt film are, for example, as follows. A substrate temperature is 350° C., Ar gas is used as a gas introduced into a film formation chamber, a pressure in the film formation chamber is 1 Pa, and a supply power is 0.3 kW. 
     Note that an Ir film, a Ru film, a RuO 2  film, a SrRuO 2  film, or a layered film thereof may be used as the conductive film  44 . 
     Next, an amorphous noble metal oxide film  45  is formed on the conductive film  44  by, for example, a sputtering method. The noble metal element contained in the noble metal oxide film  45  is preferably the same as the noble metal element contained in the conductive film  44 . Here, a PtOx (platinum oxide) film is formed as the noble metal oxide film  45 . In this case, the PtOx film is converted into a Pt film by being reduced in a heat treatment process to be described later. Note that the noble metal oxide film  45  may be formed of IrOx, SrRuO 3 , or LaSrCoO 3 . 
     When the film thickness of the noble metal oxide film  45  is less than 0.1 nm, the amount of oxygen released from the noble metal oxide film  45  in the heat treatment process to be described later is so small that the oxygen deficiency in a dielectric film  50  formed on the noble metal oxide film  45  may not be compensated sufficiently. On the other hand, when the film thickness of the noble metal oxide film  45  is more than 3 nm, it is difficult to transfer the crystallinity of the conductive film  44  to the dielectric film  50  through the noble metal oxidation  45 . For this reason, the thickness of the noble metal oxide film  45  is preferably 0.1 nm to 3 nm. 
     Next, a step of obtaining the structure in  FIG. 10G  is described. After the formation of the noble metal oxide film  45  in the above-described step, a dielectric film  50  made of a ferroelectric material is formed on the noble metal oxide film  45  by, for example, a high-frequency sputtering method. In the first embodiment, a PZT film to which Ca, Sr, and La are added, i.e. a CSPLZT film is used as the dielectric film  50 . The film thickness of the dielectric film  50  is, for example, 30 nm to 150 nm, and preferably 50 nm to 120 nm. In the first embodiment, the film thickness of the dielectric film  50  is 70 nm. 
     The temperature during the film formation of the dielectric film  50  is preferably 30° C. to 100° C. If the film formation temperature of the dielectric film  50  is lower than 30° C., the in-plane variation of the film thickness of the dielectric film  50  is great, and the crystallinity becomes heterogeneous. On the other hand, if the film formation temperature of the dielectric film  50  is higher than 100° C., the percentages of the (101) orientation and the (100) orientation is increased in the dielectric film  50 , and the percentage of the (111) orientation is reduced, so that the characteristics of the ferroelectric capacitor  62  deteriorate. In the first embodiment, the film formation temperature of the dielectric film  50  is 50° C. 
     Note that the dielectric film  50  may be formed by a method other than the sputtering method, such as a MOCVD (Metal Organic chemical Vapor Deposition) method, a sol-gel method, a MOD (Metal-Organic Decomposition) method, a CSD (Chemical Solution Deposition) method, a CVD method, an epitaxial growth method, or the like. Moreover, the dielectric film  50  may be formed of a ferroelectric material other than PZT (Pb(Zr,Ti)O 3 ), such as PLZT ((Pb,La)(Zr,Ti)O 3 ), BST (Ba x Sr 1-x )TiO 3 ), BLT ((Bi,La) 4 Ti 3 O 12 ), or BFO (BiFeO 3 ). 
     Next, a method of obtaining the structure in  FIG. 10H  is described. After the formation of the dielectric film  50  in the above-described step, the dielectric film  50  is crystallized by carrying out a rapid heat treatment (rapid thermal annealing, hereinafter referred to as RTA). Specifically, the semiconductor substrate  10  is held in an atmosphere of a mixture gas containing an inert gas (for example, Ar) and O 2  (oxygen) at a temperature of 550° C. to 650° C. for approximately 90 seconds. To improve the crystallinity of the dielectric film  50 , the flow rate of the O 2  gas is preferably 20 sccm to 70 sccm. 
     In the first embodiment, the dielectric film  50  is formed on the noble metal oxide film  45 , and the dielectric film  50  is crystallized by the heat treatment. Hence, even when the crystallinity of the conductive film  44  is insufficient, a dielectric film  50  with a favorable crystallinity may be obtained. In addition, the amorphous noble metal oxide film (PtOx film)  45  is reduced in the heat treatment, and converted into a noble metal film (Pt film)  46 . Moreover, oxygen is released from the noble metal oxide film  45  during the heat treatment. The oxygen released from the noble metal oxide film  45  compensates the oxygen deficiency in the dielectric film  50 . As a result, a dielectric film  50  having a favorable crystallinity and favorable ferroelectric characteristics may be obtained. 
     Next, a step of obtaining the structure in  FIG. 10I  is described. After the crystallization of the dielectric film  50  by the above-described heat treatment process, an amorphous conductive oxide film  52  is formed on the dielectric film  50  by, for example, a sputtering method. Specifically, a conductive oxide film  52  is formed by a high-frequency sputtering method using a target of a ferroelectric material to which a conductive material such as Ir or Ru is added, i.e., (Pb(Zr,Ti,Ir)O 3  or Pb(Zr,Ti,Ru)O 3 , or the like. At this time, the film formation temperature is room temperature to 50° C., Ar gas is supplied to a film formation chamber at a flow rate of 14 sccm to 20 sccm, and the pressure in the film formation chamber is 1 Pa, for example. For example, PZT, PLZT, CSPLZT, BST, BLT, BFO, or the like may be used as the ferroelectric material to be used as the target. 
     Note that the conductive oxide film  52  may be formed by a method such as a MOCVD method, a sol-gel method, a MOD method, a CSD method, a CVD method, or an epitaxial growth method. 
     If the percentage content of the conductive material in the conductive oxide film  52  is less than 0.8 mol %, a sufficient conductivity may not be provided to the conductive oxide film  52 . If the percentage content is not less than 1.0 mol %, the resistance of the conductive oxide film  52  is sharply reduced. For this reason, the percentage content of the conductive material in the conductive oxide film  52  is preferably 1.0 mol % or more, and further preferably 2 mol % or more. On the other hand, if the percentage content of the conductive material in the conductive oxide film  52  exceeds 4.0 mol %, the amount of the conductive material diffused from the conductive oxide film  52  to the dielectric film  50  is increased, so that the effect of suppressing the formation of the paraelectric layer may not be obtained sufficiently. 
     For this reason, the percentage content of the conductive material in the conductive oxide film  52  is preferably 1.0 mol % to 4.0 mol %. In the first embodiment, the conductive oxide film  52  is formed of a PZT having an Ir percentage content of 2 mol % (hereinafter also referred to as PZT(Ir)). 
     Moreover, if the film thickness of the conductive oxide film  52  is too small, the effect of improving the characteristics of the ferroelectric capacitor is not sufficient. Meanwhile, if film thickness is too large, the resistance of the upper electrode  60  is increased, and the processability (etching property) becomes poor. For this reason, the thickness of the conductive oxide film  52  is preferably 0.1 nm to 50 nm, and further preferably 5.0 nm to 40 nm. 
     Next, a step of obtaining the structure in  FIG. 10J  is described. After the formation of the conductive oxide film  52  in the above-described step, a conductive film  56  made of, for example, IrOx (iridium oxide) and having a thickness of 20 nm to 50 nm is formed on the conductive oxide film  52 . The conductive film  56  may be formed by use of, for example, a reactive sputtering apparatus with Ir being used as a target. The conditions for the formation of the conductive film  56  are, for example, as follows. A substrate temperature is 150° C. to 350° C., a mixture gas containing Ar and O 2  is introduced into a film formation chamber of the sputtering apparatus. In this case, for example, the flow rate of the O 2  gas is 60 sccm, the pressure in the film formation chamber is 2.0 Pa, and the supply power is about 1 kW. When the conductive film  56  is formed under such conditions at a relatively high-temperature, the conductive film  56  is already crystallized at the formation of the film. 
     Next, the semiconductor substrate  10  on which the conductive film  56  is formed is subjected to a heat treatment (RTA), for example, in an atmosphere containing oxygen. The heat treatment further improves the crystallinity of the dielectric film  50 , and the conductive oxide film  52  crystallizes while succeeding to the crystallinity of the dielectric film  50 . At this time, the Ir percentage content in the conductive oxide film  52  is as less as 1.0 mol % to 4.0 mol %, and most of Ir is incorporated into the crystals of the ferroelectric. For this reason, the amount of Ir diffused from the conductive oxide film  52  to the dielectric film  50  is small. 
     Next, an IrOx (provided that 0&lt;x≦2) film having a thickness of 70 nm to 200 nm is formed on the conductive film  56  as a conductive film  58  by, for example, a sputtering method. In this case, the composition ratio of oxygen in the IrOx film forming the conductive film  58  is preferably greater than the composition ratio of oxygen in the IrOx film forming the conductive film  56 . This enhances the effect of preventing the diffusion of hydrogen to the dielectric film  50 , so that the conductive film  58  sufficiently functions also as a hydrogen barrier film. 
     In the formation of the conductive film  58  by a sputtering method, for example, Ar gas at a flow rate of 100 sccm and O 2  gas at a flow rate of 100 sccm are supplied into a film formation chamber of a sputtering apparatus. In addition, the pressure in the film formation chamber is 0.8 Pa, the supply power is 1.0 kW, and the film formation time is about 59 seconds. When the conductive film  58  is formed under such conditions, the conductive film  58  has a thickness of approximately 150 nm. 
     Next, the dielectric film attached to the back surface of the semiconductor substrate  10  is removed by conducting a cleaning treatment. Thereafter, a TiN film having a thickness of approximately 34 nm is formed as a protection film  92  on the conductive film  58  by, for example, a sputtering method. The protection film  92  has a barrier function against reducing substances, and also functions as a hard mask used when the conductive film  56  and the conductive film  58  are patterned as described later. 
     In the formation of the protection film  92 , a Ti target is used, the substrate temperature is 150° C., and a mixture gas containing Ar and N 2  (nitrogen) is used as a gas introduced into a film formation chamber, for example. The flow rate of the Ar gas is, for example, 50 sccm, and the flow rate of the N 2  gas is, for example, 90 sccm. 
     Note that, a TiN film is used as the protection film  92  in the first embodiment. However, a TaN film, a TiON film, a TiOx film, a TaOx film, a TaON film, a TiAlOx film, a TaAlOx film, a TiAlON film, a TaAlON film, a TiSiON film, a TaSiON film, a TiSiOx film, a TaSiOx film, an AlOx film, a ZrOx film, or the like may be used as the protection film  92 . 
     Next, a step of obtaining the structure in  FIG. 10K  is described. After the formation of the protection film  92  in the above-described step, a photoresist film  94  is formed on the protection film  92  by, for example, a spin coating method. Then, the photoresist film  94  is patterned into a predetermined shape by conducting an exposure process and a development process. Thereafter, the protection film  92 , the conductive film  58 , and the conductive film  56  are sequentially etched by use of the photoresist film  94  as a mask. 
     Next, a step of obtaining the structure in  FIG. 10L  is described. After the etching of the protection film  92 , the conductive film  58 , and the conductive film  56  in the above-described step, the photoresist film  94  is peeled off. Thereafter, the protection film  92  is removed by, for example, dry etching. 
     Next, the semiconductor substrate  10  is subjected to a heat treatment in an atmosphere containing oxygen. The heat treatment is intended to recover the damage inflicted on the dielectric film  50  during the previous steps. The temperature of the heat treatment is, for example, 600° C. to 700° C. In the first embodiment, the heat treatment is conducted at a temperature of 650° C. for 40 minutes. 
     Next, a photoresist is applied onto the entire top surface of the semiconductor substrate  10 , and then an exposure process and a development process are conducted. Thus, a photoresist film  96  is formed which covers a predetermined region (upper electrode formation region) including the conductive film  58  and the conductive film  56 . Thereafter, the conductive oxide film  52  and the dielectric film  50  are etched by use of the photoresist film  96  as a mask. In this manner, the dielectric film  50  is patterned into a predetermined shape, and an upper electrode  60  is formed by the conductive oxide film  52 , the conductive film  56 , and the conductive film  58 . 
     Next, a step of obtaining the structure of  FIG. 10M  is described. After the completion of the patterning of the dielectric film  50  and the formation of the upper electrode  60  in the above-described step, the photoresist film  96  is peeled off. Thereafter, the damage inflicted on the dielectric film  50  is recovered by conducting a heat treatment, for example, in an oxygen atmosphere at a temperature of 300° C. to 650° C. for 30 minutes to 120 minutes. 
     Next, a protection film  64  is formed on the entire top surface of the semiconductor substrate  10  by, for example, a sputtering method or a CVD method. The protection film  64  is intended to prevent the entry of hydrogen and water to the ferroelectric capacitor  62 . The protection film  64  is made of, for example, an insulating material such as AlOx (aluminum oxide), and has a thickness of, for example, 20 nm to 50 nm. Note that, the protection film  64  may be formed of TiOx (titanium oxide), TaOx (tantalum oxide), ZrOx (zirconium oxide), TaN (tantalum nitride), AlN (aluminum nitride), AlON (aluminum oxynitride), or the like. 
     When the protection film  64  is formed of AlOx, for example, a reactive RF sputtering apparatus and an AlOx target are used. In addition, Ar gas is introduced into a film formation chamber of the sputtering apparatus, the pressure in the film formation chamber is approximately 1.0 Pa, the temperature during the film formation is room temperature, the supply power is 2.0 kW, and the film formation time is 40 seconds to 100 seconds, for example. 
     After the formation of the protection film  64 , a heat treatment is conducted at a temperature of, for example, 400° C. to 600° C. for 30 minutes to 120 minutes. 
     Next, a step of obtaining the structure of  FIG. 10N  is described. After the formation of the protection film  64  in the above-described step, a photoresist film  98  is formed on the entire surface of the protection film  64 , and an exposure process and a development process are conducted. Thus, the photoresist film  98  is patterned into a predetermined shape (shape of a lower electrode). 
     Next, the protection film  64 , the noble metal film  46 , the conductive film  44 , and the adhesion layer  43  are sequentially etched by use of the photoresist film  98  as a mask. The conductive film  44  and the noble metal film  46  remaining after the etching form the lower electrode  48 . Thus, a ferroelectric capacitor  62  is formed. 
     Next, a step of forming the structure in  FIG. 10O  is described. After the etching of the protection film  64 , the noble metal film  46 , the conductive film  44 , and the adhesion layer  43  in the above-described step, the photoresist film  98  is peeled off. Thereafter, water and impurities are removed by subjecting the semiconductor substrate  10  to a heat treatment, for example, in an atmosphere containing oxygen or containing oxygen and an inert gas at a temperature of 200° C. to 400° C. for 30 minutes to 120 minutes. 
     Next, a protection film  66  is formed by depositing an insulating material such as AlOx on the entire top surface of the semiconductor substrate  10  by, for example, a sputtering method or a CVD method. Thus, the ferroelectric capacitor  62  is covered with the protection film  66 . When the protection film  66  is formed by a sputtering method, the film thickness is preferably 10 nm to 30 nm, and may be 20 nm, for example. Meanwhile, when the protection film  66  is formed by a CVD method, the film thickness is preferably 1 nm to 3 nm, and, may be 2 nm, for example. 
     When the protection film  66  is formed of AlOx, a reactive RF sputtering apparatus is used, for example. Here, Ar gas is introduced into a film formation chamber of the sputtering apparatus, the pressure in the film formation chamber is approximately 1.0 Pa, the temperature during film formation is room temperature, the supply power is 2.0 kW, and the film formation time is approximately 40 seconds. As a result, a very dense protection film  66  made of AlOx may be obtained. Note that the protection film  66  may be formed of TiOx, TaOx, ZrOx, TaN, AlN, AlON, or the like. 
     Next, the semiconductor substrate  10  is subjected to a heat treatment, for example, in an atmosphere containing oxygen at a temperature of 500° C. to 700° C. for 30 minutes to 120 minutes. The heat treatment is intended to recover the damage inflicted on the dielectric film  50  by the sputtering, and to improve the electrical characteristics of the ferroelectric capacitor  62 . 
     Next, a step of obtaining the structure of  FIG. 10P  is described. After the heat treatment is conducted on the protection film  66  in the above-described step, an interlayer insulating film  68  is formed on the protection film  66  by, for example, a plasma TEOS CVD method. The interlayer insulating film  68  is formed of, for example, SiO 2 , and has a thickness of, for example, 1.4 μm. 
     Next, the surface of the interlayer insulating film  68  is polished and flattened by, for example, a CMP method. Thereafter, a heat treatment is conducted in a plasma atmosphere generated by use of, for example, N 2 O gas or N 2  gas at a temperature of 350° C. for 2 minutes. The heat treatment is intended to remove water in the interlayer insulating film  68 , and to change the film quality of the interlayer insulating film  68 . After the heat treatment, the interlayer insulating film  68  is more resistant to entry of water. 
     Next, a step of obtaining the structure of  FIG. 10Q  is described. After the formation of the interlayer insulating film  68  in the above-described step, a protection film  70  having a thickness of 20 nm to 50 nm is formed on the interlayer insulating film  68  by, for example, a sputtering method or a CVD method. The protection film  70  is formed of an insulating material such as AlOx. 
     Next, an interlayer insulating film  72  having a thickness of about 300 nm and made of an insulating material such as SiO 2  is formed on the protection film  70  by, for example, a plasma TEOS CVD method. 
     Next, a step of obtaining the structure of  FIG. 10R  is described. After the formation of the interlayer insulating film  72  in the above-described step, a contact hole  74   a  and a contact hole  74   b  are formed by employing a photolithography method and a etching method. The contact hole  74   a  extends from the top surface of the interlayer insulating film  72  to the lower electrode  48 , and the contact hole  74   b  extends from the top surface of the interlayer insulating film  72  to the upper electrode  60 . 
     Thereafter, a heat treatment is conducted, for example, in an oxygen atmosphere at a temperature of 400° C. to 600° C. for 30 minutes to 120 minutes. The heat treatment is intended to supply oxygen to the dielectric film  50 , and to thereby improve the electrical characteristics of the ferroelectric capacitor  62 . 
     Next, a step of obtaining the structure in  FIG. 10S  is described. After the heat treatment conducted in the above-described step, a contact hole  76  extending from the top surface of the interlayer insulating film  72  to the conductive plug  36  is formed by use of a photolithography method and an etching method. 
     Next, a step of obtaining the structure in  FIG. 10T  is described. After the formation of the contact hole  76  in the above-described step, an adhesion layer  78  is formed on the entire top surface of the semiconductor substrate  10  by, for example, a sputtering method. Thus, inner surfaces of the contact holes  74   a ,  74   b , and  76  are covered with the adhesion layer  78 . 
     The adhesion layer  78  is formed of, for example, TiN, and has a thickness of, for example, 50 nm to 150 nm. When a TiN film is formed as the adhesion layer  78 , Ti is used as a target. In addition, the atmosphere in the film formation chamber is an atmosphere of a mixture of Ar gas and N 2  gas. The flow rate of the Ar gas is, for example, 50 sccm, and the flow rate of the N 2  gas is, for example, 90 sccm. The film formation temperature is, for example, 150° C. 
     Next, a conductive material such as W (tungsten) is deposited on the entire top surface of the semiconductor substrate  10  by, for example, a CVD method. Thus, the conductive material is filled into the contact holes  74   a ,  74   b , and  76 . Thereafter, the conductive material and the adhesion layer  78  on the interlayer insulating film  72  are polished and removed by, for example, a CMP method to an extent that the surface of the interlayer insulating film  72  is exposed. Thus, a conductive plug  80   a , a conductive plug  80   b , and a conductive plug  80   c  are formed. The conductive plug  80   a  is electrically connected to the lower electrode  48 , the conductive plug  80   b  is electrically connected to the upper electrode  60 , and the conductive plug  80   c  is electrically connected to the transistor  26  through the conductive plug  36 . 
     Next, a step of obtaining the structure in  FIG. 10U  is described. After the formation of the conductive plugs  80   a ,  80   b , and  80   c  in the above-described step, the semiconductor substrate  10  is subjected to plasma cleaning. A gas used for the plasma cleaning is, for example, Ar gas. As a result, natural oxidation films and the like present on the surfaces of the conductive plugs  80   a  to  80   c  are removed. 
     Next, a TiN film  82 , an Al Cu alloy film  84 , a Ti film  86 , and a TiN film  88  are sequentially formed on the entire top surface of the semiconductor substrate  10  by, for example, a sputtering method. In this case, the TiN film  82  has a thickness of 50 nm, the Al Cu alloy film  84  has a thickness of 550 nm, the Ti film  86  has a thickness of 5 nm, and the TiN film  88  has a thickness of 50 nm, for example. 
     Next, the TiN film  82 , the AlCu alloy film  84 , the Ti film  86 , and the TiN film  88  are patterned by conducting a photolithography process and an etching process. Thus, wirings  90  are formed. Each of the wirings  90  has a structure in which the TiN film  82 , the Al Cu alloy film  84 , the Ti film  86 , and the TiN film  88  are staked. Note that the material and the layer structure of the wiring  90  may be changed as appropriate. 
     Subsequently, interlayer insulating films, conductive plugs, wirings, and the like are further formed, if necessary, to obtain a multilayer wiring structure. A semiconductor device according to the first embodiment is thus completed. 
     Note that the case where the conductive oxide film is formed by sputtering the ferroelectric material to which Ir is added is described in the first embodiment. However, the conductive oxide film  52  may be formed by first forming a non-crystalline (amorphous) dielectric film, and then introducing a metal element such as Ir or Ru into the dielectric film. 
     For example, an amorphous dielectric film having a thickness of 10 nm to 30 nm and having the same composition as the dielectric film  50  is formed on the crystallized dielectric film  50 . Thereafter, an IrOx film (conductive film  56 ) is formed on the amorphous dielectric film. Then, a heat treatment (RTA) is conducted to diffuse Ir contained in the IrOx film into the amorphous dielectric film. Thus, the conductive oxide film  52  is formed. 
     In this method, the film formation temperature of the IrOx film influences the characteristics of the ferroelectric capacitor. If the film formation temperature is 200° C. or above, the IrOx film is crystallized simultaneously with the film formation, and Ir is diffused into the amorphous dielectric film. Then, when the amorphous dielectric film is crystallized, Ir diffused in the amorphous dielectric film is incorporated into the crystals. As a result, a conductive oxide film  52  having the same crystal structure as the dielectric film  50  is formed. 
     In this case, since the IrOx film (conductive film  56 ) is already crystallized, Pb in the amorphous dielectric film is hard to diffuse into the IrOx film. As a result, no paraelectric layer is formed between the IrOx film (conductive film  56 ) and the conductive oxide film  52 . 
     On the other hand, when the film formation temperature of the IrOx film is lower than 200° C., Ir hardly diffuses from the IrOx film to the amorphous dielectric film during the film formation. In addition, when the amorphous dielectric film is crystallized, interdiffusion of Ir and Pb occurs between the IrOx film (conductive film  56 ) and the amorphous dielectric film, so that a paraelectric layer is formed at an interface between the IrOx film (conductive film  56 ) and the dielectric film (the film formed after crystallization of the amorphous dielectric film). 
     For this reason, when the conductive oxide film  52  is formed by the above-described method, the film formation temperature of the IrOx film (conductive film  56 ) is preferably 200° C. or above. 
       FIG. 11A  is a cross-sectional view of a ferroelectric capacitor  62  formed by the above-described method on the semiconductor substrate  10 , and  FIG. 11B  is a diagram schematically illustrating a layer structure of the ferroelectric capacitor  62 . 
     As illustrated in  FIG. 11A , the ferroelectric capacitor  62  of a semiconductor device according to the first embodiment has a noble metal film  46  (lower electrode), a dielectric film  50 , and an upper electrode  60 . The upper electrode  60  has a layered structure of a conductive oxide film  52 , a conductive film  56 , and a conductive film  58 . 
     As illustrated in  FIG. 11B , Pt forming the noble metal film  46  has a columnar crystal structure, and PZT (perovskite crystal) forming the dielectric film  50  grows on the crystals of the noble metal film  46 . Then, PZT forming the conductive oxide film  52  also grows while succeeding to the crystallinity of the dielectric film  50  to have a columnar perovskite structure. 
     Ir added to the conductive oxide film  52  is incorporated into the crystals, and Ir is hardly present at the grain boundaries. Moreover, the Ir percentage content in the conductive oxide film  52  is as small as about 1 mol % to 4 mol %. For this reason, even when a heat treatment is conducted, the amount of Ir diffused from the conductive oxide film  52  to the dielectric film  50  is small, and no paraelectric layer (dead layer) is formed at the interface between the upper electrode  60  and the dielectric film  50 . If the paraelectric layer is formed, the film thickness thereof is small. Note that interdiffusion between Pb in the dielectric film  50  and Pb in the conductive oxide film  52  may possibly occur, but the interdiffusion between Pb and Pd does not results in the formation of the paraelectric layer. 
     Hereinafter, description is made of results obtained when the Ir concentration distribution near the interface between a dielectric film and an upper electrode is measured by use of a secondary ion mass spectrometer (SIMS). 
     First, a capacitor having the structure of  FIGS. 11A and 11B  is produced as Example. Specifically, a PZT film (dielectric film  50 ) having a thickness of 130 nm is formed on a Pt film (noble metal film  46 ), and is subjected to a crystallization treatment (heat treatment). Thereafter, an amorphous PZT film having a thickness of 20 nm is formed on the PZT film, and an IrO 2  film (conductive film  56 ) is formed on the amorphous PZT film. The temperature during the formation of the IrO 2  film is 300° C., so that Ir is diffused into the amorphous PZT film simultaneously with the formation of the IrO 2  film. 
     Subsequently, a heat treatment is conducted in an atmosphere of a mixture of Ar and O 2  at a temperature of 725° C. Thus, the amorphous PZT is crystallized to form a conductive oxide film  52  (PZT(Ir)film). 
     On the other hand, a capacitor having the structure of  FIGS. 1A and 1B  is formed as Comparative Example 1, and a capacitor having the structure of  FIGS. 5A and 5B  is formed as Comparative Example 2. The methods for forming Pt films (lower electrode films  211  and  221 ), PZT films (dielectric films  212 ,  222 , and  223 ), and IrO 2  films (electrode films  213  and  224 ) are basically the same as those in the above-described Example. The thickness of the PZT film of Comparative Example 1 is 150 nm. The thickness of the first PZT film of Comparative Example 2 is 130 nm, and the thickness of the second PZT film is 20 nm. 
       FIG. 12A  is a diagram illustrating an example of results obtained by investigating the Ir concentration distribution in the ferroelectric capacitor of Example. In  FIG. 12A , the horizontal axis represents the depth, and the vertical axis represents the concentration. Meanwhile,  FIG. 12B  is a diagram illustrating an example of results obtained by investigating the Ir concentration distribution of the ferroelectric capacitor of each of Comparative Examples 1 and 2. In  FIG. 12B , the horizontal axis represents the depth, and the vertical axis represents the concentration. Note that, in Example, the interface between the PZT(Ir) film and the PZT film is the interface between the upper electrode and the dielectric film, whereas, in each of Comparative Examples 1 and 2, the interface between the IrO 2  film and the PZT film is the interface between the upper electrode and the dielectric film. 
     It is understood from  FIGS. 12A and 12B  that the Ir concentration near the interface between the upper electrode and the dielectric film is lower in the ferroelectric capacitor of Example than in each of the ferroelectric capacitors of Comparative Examples 1 and 2 by one order of magnitude or more. 
       FIG. 13  is a diagram illustrating an example of results obtained by investigating the relationship between the Ir percentage content and the resistivity. In  FIG. 13 , the horizontal axis represents the Ir percentage content in PZT, and the vertical axis represents the resistivity. When the Ir percentage content in the PZT is 0.6 mol % or less, the resistivity is large, and the PZT exhibits electrical insulation characteristics. When the Ir percentage content in the PZT is 0.8 mol %, the resistivity is measurable, but the resistivity is so large that the PZT is not usable as an electrode. 
     When the Ir percentage content is 1.0 mol % or more, the resistivity is so small that the PZT is usable as an electrode. Moreover, when the Ir percentage content is not less than 2.0 mol %, the PZT exhibits a favorable electrical conductivity. It is understood from  FIG. 13  that the Ir percentage content of the conductive oxide film  52  may be 1 mol % or more, and more preferably 2 mol % or more. 
       FIG. 14  is a graph illustrating an example of the relationship between the switching charge Qsw and the applied voltage (Qtv characteristics) of the ferroelectric capacitors of Examples where the film thickness of the dielectric films (PZT film) are 90 nm, 100 nm, and 120 nm, respectively. In  FIG. 14 , the horizontal axis represents the applied voltage, and the vertical axis represents the switching charge Qsw. Note that the thickness of the conductive oxide film (PZT(Ir)film) of each of these ferroelectric capacitors is 20 nm. 
     Meanwhile,  FIG. 15  is a diagram illustrating an example of the saturation charge Qt of each of these ferroelectric capacitors.  FIG. 16  is a diagram illustrating an example of the V50 of each of these ferroelectric capacitors. 
     Note that  FIGS. 14 to 16  also illustrate the Qtv characteristics, the saturation charge Qt, and the V50 of a ferroelectric capacitor having the structure of  FIGS. 1A and 1B  as a comparative example. The film thickness of the dielectric film (PZT film) of the ferroelectric capacitor of the comparative example is 100 nm. 
     As understood from  FIG. 14 , even when the film thickness of the dielectric film (PZT film) is changed among the ferroelectric capacitors of Examples, almost no change is observed in the curve (Qtv characteristics) representing the relationship between the switching charge Qsw and the applied voltage V. Moreover, as understood from  FIG. 15 , the value of the saturation charge Qt is almost constant among the ferroelectric capacitors of Examples, irrespective of the film thickness of the dielectric film (PZT). Moreover, as understood from  FIG. 16 , as the thickness of the dielectric film (PZT film) becomes smaller, the value of V50 becomes smaller, in the case of the ferroelectric capacitors of Examples. It is understood from these results that each of the ferroelectric capacitors of Examples is improved in terms of the interface between the dielectric film and the upper electrode when compared with the ferroelectric capacitor of the comparative example. 
     Moreover, in the cases of the ferroelectric capacitors of Examples, the Qtv characteristics hardly change even when the film thickness of the dielectric film is reduced. From this result, it is understood that desired characteristics may be obtained by a ferroelectric capacitors of Example, even when the film thickness of the dielectric film is reduced. Moreover, in the case of the ferroelectric capacitors of Examples, the value of the V50 is reduced as the ferroelectric film is made thinner. From this result, it is understood that each of the ferroelectric capacitors of Examples may be operated at a low voltage by making the film thickness of the dielectric film smaller. 
       FIG. 17  is a diagram illustrating an example of the relationship between the switching charge Qsw and the applied voltage V (Qtv characteristics) of the ferroelectric capacitors of Examples where the film thicknesses of the conductive oxide films (PZT(Ir) films) are 10 nm, 15 nm, and nm, respectively. In  FIG. 17 , the horizontal axis represents the applied voltage, and the vertical axis represents the switching charge Qsw. Note however that the film thickness of the dielectric film (PZT film) of each of these ferroelectric capacitors is 90 nm. 
     Meanwhile,  FIG. 18  is a diagram illustrating an example of the saturation charge Qt of each of these ferroelectric capacitors, and  FIG. 19  is a diagram illustrating an example of the V50 of each of these ferroelectric capacitors. 
     Note that  FIG. 17  to  FIG. 19  also illustrate the Qtv characteristics, the saturation charge Qt, and the V50 of a ferroelectric capacitor having the structure of  FIGS. 1A and 1B  as a comparative example. The film thickness of the dielectric film (PZT film) of the ferroelectric capacitor of the comparative examples is 90 nm. 
     As seen from  FIG. 17 , in the case of the ferroelectric capacitors of Examples, the curve (Qtv characteristics) representing the relationship between the switching charge Qtv and the applied voltage V hardly changes, even when the film thickness of the conductive oxide film (PZT(Ir)film) is changed. Moreover, as understood from  FIGS. 18 and 19 , the values of the saturation charge Qt and the V50 are almost constant among the ferroelectric capacitors of Examples, irrespective of the film thickness of the conductive oxide film (PZT(Ir) film). From there results, it is understood that, in the case of the ferroelectric capacitors of Examples, the film thickness of the conductive oxide film does not greatly influence the characteristics of the ferroelectric capacitors. 
       FIG. 20  is a graph illustrating an example of the relationship between the switching charge Qsw and the applied voltage V (Qtv characteristics) of the ferroelectric capacitors of Examples among which the film thickness of the dielectric film (PZT film) is changed in the range from 60 nm to 100 nm. In  FIG. 20 , the horizontal axis represents the applied voltage, and the vertical axis represents the switching charge Qsw. Note that the thickness of the conductive oxide film (PZT(Ir) film) of each of these ferroelectric capacitors is 15 nm. 
     Moreover,  FIG. 21  is a diagram illustrating an example of the saturation charge Qt of each of these ferroelectric capacitors, and  FIG. 22  is a diagram illustrating an example of the V50 of each of these ferroelectric capacitors. 
     From  FIGS. 20 to 22 , it is understood that, in the case of the ferroelectric capacitors of Examples, the switching charge Qsw and the saturation charge Qt hardly change, even when the film thickness of the dielectric film (PZT film) is reduced to 60 nm. Moreover, in the case of the ferroelectric capacitors of Examples, the value of the V50 becomes smaller as the dielectric film (PZT film) becomes thinner. 
     In each of the ferroelectric capacitors of Examples, the conductive oxide film  52  having a perovskite structure is formed on the dielectric film  50 . This improves the interface between the upper electrode  60  and the dielectric film  50 , and a paraelectric layer is hardly formed between the upper electrode  60  and the dielectric film  50 . Accordingly, a large saturation charge Qt may be obtained even when the film thickness of the dielectric film  50  is reduced, and hence the ferroelectric capacitor may be operated at a low voltage. 
       FIG. 23  is a graph illustrating an example of results obtained when a ferroelectric capacitor of Example is subjected to a stress test in which data are repeatedly written and deleted in an atmosphere at 90° C. In  FIG. 23 , the horizontal axis represents the stress cycle, and the vertical axis represents the switching charge Qsw. Note that, in the ferroelectric capacitor of Example, the film thickness of the dielectric film (PZT film) is 90 nm, and the film thickness of the conductive oxide film (PZT(Ir) film) is 15 nm. In addition, the voltage supplied to the ferroelectric capacitor during the stress test is 5 V, and the voltage supplied to the ferroelectric capacitor for the measurement of the switching charge Qsw is 1.8 V. 
     Moreover, a ferroelectric capacitor having the structure of  FIGS. 1A and 1B  is produced as Comparative Example 3, and ferroelectric capacitors having the structure of  FIGS. 5A and 5B  are produced as Comparative Examples 4 and 5. These ferroelectric capacitors are also subjected to the stress test. The thickness of the dielectric film (PZT film) in the ferroelectric capacitor of Comparative Example 3 is 120 nm, the film thickness of the dielectric film in the ferroelectric capacitor of Comparative Example 4 is 120 nm (90 nm+30 nm), and the film thickness of the dielectric film in the ferroelectric capacitor of Comparative Example 5 is 140 nm (130 nm+10 nm). 
     Moreover,  FIG. 24  is a diagram illustrating an example of fatigue loss of the ferroelectric capacitors of Example and Comparative Examples 3 to 5. The fatigue loss is calculated by 100×((Qsw1−Qsw2)/Qsw1), where Qsw1 represents the initial value of the switching charge Qsw of a ferroelectric capacitor, and Qsw2 represents the switching charge of the ferroelectric capacitor subjected to 10 10  cycles in the cycle test illustrated in  FIG. 23 . A smaller value of the fatigue loss indicates that the ferroelectric capacitor is more resistant to degradation. 
     As understood from  FIGS. 23 and 24 , the fatigue resistance characteristics of the ferroelectric capacitor of Example are better than those of the ferroelectric capacitors of Comparative Examples 3 and 4. Although the film thickness of the dielectric film (PZT film) in the ferroelectric capacitor of Example is as thin as 90 nm, the ferroelectric capacitor of Example has fatigue resistance characteristics almost equivalent to those of the ferroelectric capacitor of Comparative Example 5 where the film thickness of the dielectric film is 140 nm. 
     Second Embodiment 
       FIG. 25  is a view for describing a semiconductor device and a manufacturing method thereof according to a second embodiment. The second embodiment is described while a stack-type FeRAM is taken as an example. 
     First, as in the case of the first embodiment, an element isolation film  12  and a well  14  are formed in a semiconductor substrate (silicon substrate)  10 , and source and drain regions  22 , gate insulating films  16 , and gate electrodes  18  of transistors  26  are formed. In addition, side walls  20  are formed on the sides of the gate electrode  18 , a silicide film  24   a  is formed on the gate electrode  18 , and a silicide film  24   b  is formed on the surface of each of the source and drain regions  22 . Note that the second embodiment is different from the first embodiment in that two transistors  26  are formed in one well  14 . 
     Next, an insulating film  28  and an interlayer insulating film  30  are sequentially formed on the entire top surface of the semiconductor substrate  10 . Then, contact holes  32  are formed which extend from the top surface of the interlayer insulating film  30  to the silicide film  24   b . Thereafter, an adhesion layer  34  is formed in each of the contact holes  32 , and a high-melting-point metal such as W (tungsten) is filled into the contact holes  32  to form conductive plugs  36 . 
     Next, a SiNO film  100  having a thickness of, for example, 130 nm is formed by a plasma CVD method on the entire top surface of the semiconductor substrate  10 , and then a SiO 2  film  102  having a thickness of 300 nm is further formed on the SiNO film  100 . Thus, an interlayer insulating film  104  having a double layered structure is formed. 
     Thereafter, contact holes  106  are formed which extend from the top surface of the interlayer insulating film  104  to the conductive plugs  36 , and then the wall surface of each of the contact holes  106  is covered with an adhesion layer  108 . The adhesion layer  108  has, for example, a double layered structure of a Ti film having a thickness of 30 nm and a TiN film having a thickness of 20 nm. Then, a high-melting-point metal such as W (tungsten) is filled into the contact holes  106  to form conductive plugs  110 . 
     Next, a Ti film having a thickness of 100 nm to 300 nm is formed on the entire top surface of the semiconductor substrate  10 , for example, by a sputtering method. Then, the semiconductor substrate  10  is subjected to a heat treatment (RTA) in a nitrogen atmosphere, for example, at a temperature of 650° C. for 60 seconds. The heat treatment converts the Ti film into a TiN film. The TiN film is used as an underlayer film  114 . 
     Next, the surface of the underlayer film  114  is polished by a CMP method to a film thickness of 50 nm to 100 nm. Thereafter, the surface of the underlayer film  114  is treated with plasma. Specifically, the surface of the underlayer film  114  is exposed to a plasma atmosphere generated by use of, for example, NH 3  gas. 
     Next, a Ti film having a thickness of 20 nm is formed on the underlayer film  114  by, for example, a sputtering method. Since the Ti film is formed on the plasma-treated underlayer film  114 , a Ti film with high film quality may be obtained in the second embodiment. 
     Next, a heat treatment (RTA) is conducted in a nitrogen atmosphere, for example, at a temperature of 650° C. for 60 seconds. Thus, the Ti film is converted into a TiN film with the (111) orientation, and used as an adhesion layer  116 . 
     Next, a TiAlN film having a thickness of about 10 nm is formed on the adhesion layer  116  by, for example, a reactive sputtering method, and used as an oxygen barrier film (oxygen diffusion prevention film)  118 . The oxygen barrier film  118  is intended to prevent oxidation of the top surface of each of the conductive plugs  110 . 
     Next, a noble metal film (conductive film)  44   a  made of a noble metal such as Ir and having a thickness of about 100 nm is formed on the oxygen barrier layer  118  by, for example, a sputtering method. Thereafter, a heat treatment (RTA) is conducted, for example, in an argon atmosphere at a temperature of 650° C. for 60 seconds. The heat treatment is intended to grow crystal grains of the noble metal with a uniform size in the noble metal film  44   a.    
     Next, IrOx (iridium oxide) is deposited on the noble metal film  44   a  to a thickness of 25 nm by, for example, a sputtering method. Thus, an amorphous noble metal oxide film is formed. The noble metal oxide film is to be reduced into a noble metal film  46   a  in a later stage. 
     Next, a dielectric film  50   a  made of a ferroelectric material such as PZT is formed on the noble metal oxide film by, for example, a MOCVD method. The thickness of the dielectric film  50   a  is preferably 30 nm to 150 nm, and more preferably 50 nm to 120 nm. 
     Next, a conductive oxide film  52  is formed on the dielectric film  50   a  by, for example, a sputtering method. As in the case of the first embodiment, the conductive oxide film  52  may be formed by, for example, a high-frequency sputtering method using a target of a ferroelectric material to which a conductive material such as Ir or Ru is added. 
     Next, the semiconductor substrate  10  is subjected to a heat treatment (RTA) in an atmosphere containing oxygen. The heat treatment is intended to further improve the crystallinity of the dielectric film  50   a , and to crystallize the amorphous conductive oxide film  52  continuously on the dielectric film  50   a . In this heat treatment, the growth of the crystals of the conductive oxide film  52  starts from crystal grains of the dielectric film  50   a . Moreover, the conductive oxide film  52  suppresses the interdiffusion of metal elements between the dielectric film  50   a  and a conductive film  56 . 
     Next, a conductive film  56  having a thickness of 20 nm to 50 nm is formed on the conductive oxide film  52  by, for example, a sputtering method. Thereafter, a conductive film  58  having a thickness of 75 nm to 200 nm is formed on the conductive film  56  by a sputtering method or the like. These conductive films  56  and  58  are formed of, for example, IrOx. 
     Next, an Ir film having a thickness of about 50 nm is formed on the conductive film  58  by, for example, a sputtering method. Thus, a hydrogen barrier film  120  is formed. Note that the hydrogen barrier film  120  has conductivity and a property of not easily allowing hydrogen permeation, and may be formed of, for example, SrRuO 3  or the like. 
     Next, a TiN film is formed on a hydrogen barrier film  120  by, for example, a sputtering method. Thus, a first protection film (not illustrated) is formed. Note that, the first protection film may be formed by a TiAlN film, a Ta film, an AlN film, a TaN film, or a layered film of any of them. 
     Next, a second protection film (not illustrated) is formed on the first protection film by, for example, a plasma TEOS CVD method. Thereafter, a photoresist film is formed on the second protection film. Then, an exposure process and a development process are conducted to leave the photoresist film in predetermined regions. Then, the second protection film is etched by using the photoresist film as a mask. Thereafter, the photoresist film is removed, and then the first protection film is etched by using the second protection film as a mask. Thus, a hard mask having a double layered structure including the first protection film and the second protection film is obtained. 
     Next, portions of the hydrogen barrier film  120 , the conductive film  58 , the conductive film  56 , the conductive oxide film  52 , the dielectric film  50   a , the noble metal film  46   a , and the conductive film  44   a  located in regions which are not covered with the hard mask are sequentially etched by, for example, plasma etching. For example, a mixture gas obtaining by mixing HBr gas, O 2  gas, Ar gas, and C 4 F 8  gas is used as the etching gas. 
     The conductive film  44   a  and the noble metal film  46   a  remaining after the etching form lower electrodes  48   a . Meanwhile, the conductive oxide film  52 , the conductive film  56 , the conductive film  58 , and the hydrogen barrier film  120  form upper electrodes  60   a . Moreover, the lower electrode  48   a , the dielectric film  50   a , and the upper electrode  60   a  form ferroelectric capacitors  62   a.    
     Next, the second protection film is removed by dry etching or wet etching. Thereafter, the oxygen barrier film  118 , the adhesion film  116 , and the underlayer film  114  are etched by, for example, dry etching. At this time, the first protection film is also removed by the etching. For the etching, for example, a down-flow plasma etching apparatus is used, and CF 4  gas (5%) and O 2  gas (95%) are supplied into the chamber. Moreover, a high-frequency power of, for example, a frequency of 2.45 GHz and 1400 W is supplied to the upper electrode of the plasma etching apparatus, and the substrate temperature is 200° C. 
     Next, aluminum oxide is deposited on the entire top surface of the semiconductor substrate  10  by, for example, a sputtering method. Thus, a protection film  122  is formed. The protection film  122  is intended to prevent reduction of the dielectric film  50   a  due to hydrogen or water. 
     Next, a heat treatment is conducted in an atmosphere containing oxygen at a temperature of 500° C. to 700° C. for 30 minutes to 120 minutes. The heat treatment is intended to recover the damage on the dielectric film  50   a  due to the sputtering, and thereby to improve the electrical characteristics of the ferroelectric capacitor  62   a.    
     Next, an aluminum oxide film  124  is formed on the protection film  122 , and then a heat treatment is conducted in an atmosphere containing oxygen or ozone. Then, a silicone oxide film having a thickness of 1.5 μm is formed on the entire top surface of the semiconductor substrate  10  by, for example, a plasma TEOS CVD method. Thus, an interlayer insulating film  68  is formed. 
     Thereafter, the surface of the interlayer insulating film  68  is flattened by a CMP method. Then, a heat treatment is conducted in a plasma atmosphere generated by using, for example, N 2 O gas or N 2  gas at a temperature of 350° C. 
     Next, a protection film  70  is formed on the interlayer insulating film  68  by, for example, a sputtering method or a CVD method. The protection film  70  is formed of, for example, aluminum oxide, and has a thickness of, for example, 20 nm to 100 nm. 
     Next, a silicon oxidation film having a thickness of 800 nm to 1 μm is formed on the protection film  70  by, for example, a plasma TEOS CVD method. Thus, an interlayer insulating film  72  is formed. Thereafter, the surface of the interlayer insulating film  72  is polished and flattened by a CMP method. 
     Next, a contact hole  126   a  and contact holes  126   b  are formed by using a photolithography method and an etching method. The contact hole  126   a  extends from the top surface of the interlayer insulating film  72  to the conductive plug  36 . The contact holes  126   b  extend from the top surface of the interlayer insulating film  72  to their respective upper electrodes  60   a . Then, the wall surface of each of the contact holes  126   a  and  126   b  is covered with an adhesion layer  128  of TiN or the like. After that, a high-melting-point metal such as W (tungsten) is filled into the contact holes  126   a  and  126   b . Thus, conductive plugs  130   a  and  130   b  are formed. 
     Next, a TiN film  82  having a film thickness of 50 nm, an Al Cu alloy film  84  having a film thickness of 550 nm, a Ti film  86  having a film thickness of 5 nm, and a TiN film  88  having a film thickness of 50 nm are sequentially formed by, for example, a sputtering method. Thereafter, a photolithography process and an etching process are conducted to pattern the TiN film  82 , the Al Cu alloy film  84 , the Ti film  86 , and the TiN film  88 . Thus, wirings  90  are formed. A semiconductor device according to the second embodiment is thus completed. 
     Also in the second embodiment, the conductive oxide film  52  of a dielectric material to which conductivity is provided by adding a metal element is formed on the dielectric film  50   a  as in the case of the first embodiment. This suppresses the formation of a paraelectric layer at the interface between the upper electrode  60   a  and the dielectric film  50   a . As a result, even when the film thickness of the dielectric film  50   a  is small, desired characteristics may be obtained. In addition, the semiconductor device may be operated at a lower voltage than conventional ones. 
     Other Embodiments 
     In the above description of the first and second embodiments, the cases where TiN films are used as the adhesion layers  78  and  128  are taken as examples. However, the adhesion layers  78  and  128  are not limited to TiN films. For example, a TaN film, a CrN film, a HfN film, a ZrN film, a TiAlN film, a TaAlN film, a TiSiN film, a TaSiN film, a CrAlN film, a HfAlN film, a ZrAlN film, a TiON film, a TaON film, a CrON film, a HfON film, or the like may be used as the adhesion layer  78  or  128 . 
     Moreover, a ZrON film, a TiAlON film, a TaAlON film, a CrAlON film, a HfAlON film, a ZrAlON film, a TiSiON film, a TaSiON film, an Ir film, a Ru film, an IrOx film, a RuOx film, or the like may be used as the adhesion layer  78  or  128 . 
     Moreover, a layered film formed by sequentially stacking a Ti film and a TiN film may be used as the adhesion layer  78  or  128 . Still moreover, a layered film formed by sequentially stacking a Ti film and a TaN film may be used as the adhesion layer  78  or  128 . Furthermore, a layered film formed by sequentially stacking a Ta film and a TiN film may be used as the adhesion layer  78  or  128 . Still furthermore, a layered film formed by sequentially stacking a Ta film and a TaN film may be used as the adhesion layer  78  or  128 . 
     In the above description of the first and second embodiments, the cases where an iridium oxide film is used as the conductive film  56  are taken as examples. However, the conductive film  56  is not limited to the iridium oxide film. For example, a conductive oxide film of an oxide of Ru, Rh, Re, Os, or Pd may be used as a material of the conductive film  56 . Moreover, a conductive oxide film of SrRuO 3  or the like may be used as a material of the conductive film  56 . Furthermore, a layered film of any of these materials may be used as the conductive film  56 . Still furthermore, a layered film of any of these conductive oxide films and a noble metal film may be used as the conductive film  56 . 
     In the above description of the first and second embodiments, the cases where an iridium oxide film is used as the conductive film  58  are taken as examples. However, the conductive film  58  is not limited to the iridium oxide film. For example, a conductive oxide film of an oxide of Ru, Rh, Re, Os, or Pd may be used as a material of the conductive film  58 . Moreover, a conductive oxide film of SrRuO 3  or the like may be used as the material of the conductive film  58 . Furthermore, a layered film of any of these materials may be used as the conductive film  58 . Still moreover, a layered film of any of these conductive oxide films and a noble metal film may be used as the conductive film  58 . 
     All examples and conditional language recited herein are intended for pedagogical purposes to aid the reader in understanding the invention and the concepts contributed by the inventor to furthering the art, and are to be construed as being without limitation to such specifically recited examples and conditions, nor does the organization of such examples in the specification relate to a illustrating of the superiority and inferiority of the invention. Although the embodiments of the present invention have been described in detail, it should be understood that the various changes, substitutions, and alterations could be made hereto without departing from the spirit and scope of the invention.