Abstract:
A semiconductor device and a wiring therefor and a fabrication method thereof are disclosed, which are capable of providing a good current driving capability without degrading the characteristic of the semiconductor device by overcoming the problems encountered in the known semiconductor device, and a wiring is implemented by using e semiconductor device fabricated in accordance with the present invention.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a semiconductor device and its wiring and a fabrication method thereof. More specifically, the present invention relates to an improved semiconductor device and its wiring and a fabrication method thereof which are implemented by serially arranging at least two films which have different materials from each other. 
     2. Description of the Background Art 
     The gate electrode of a known semiconductor device is formed in a structure where a silicide layer or a metal layer is deposited on a polysilicon layer in order to decrease resistance. The gate electrode includes wiring for transferring electrical signals therethrough. Therefore, the gate electrode represents all kinds of wiring which are used as an element of the transistor and which are used for the semiconductor device for transferring electrical signals. 
     Recently, a multilayer film gate electrode technique has been developed to form a polysilicon layer, a diffusion barrier layer and a metallic film when the ource and/or drain are formed via a self-alignment technique. In the multilayer film gate electrode technique, a dopant diffusion barrier layer consisting of a titanium nitride TiN is formed between a polysilicon layer and a suicide layer. 
     In addition, conventional devices are known to utilize a multilayer film structure of a polysilicon layer and a metal film, or a polysilicon, a diffusion barrier layer and a metal film. Also, the electrical characteristics of a gate electrode which is formed in a single layer structure of a metallic layer were reported. 
     The known wiring(gate electrode) of a semiconductor device and a wiring structure thereof will now be explained with reference to the accompanying drawings. 
     FIG. 1A illustrates the structure of a known semiconductor device. A p-type semiconductor substrate is generally used for fabricating an n-channel transistor and an n-type semiconductor substrate is used for fabricating a p-channel transistor. The semiconductor device having an n-channel transistor will now be explained 
     An insulation film  2  is formed on the upper surface of a semiconductor substrate  1  which is doped with a p-type impurity, a gate electrode  3  is formed on the insulation film  2  and a conductive n-type dopant layer  4  is formed at the surface of the semiconductor substrate  1  at both sides of the gate electrode  3 . At this time, the insulation film  2  is generally an oxide film which is formed by a thermal oxide method. Alternatively, the insulation film  2  may be an insulator having a high dielectric constant such as a nitride film. The insulation film  2  is well known as a gate oxide film. The gate electrode  3  is formed of a multilayer film having a metal layer pattern or a silicide layer pattern  3   b  deposited on a doped polysilicon layer pattern  3   a . Hereinafter, the metal layer and the silicide layer are referred as a metallic film. Therefore, the metallic film pattern  3   b denotes a metal layer pattern or a silicide layer pattern. As the metallic film pattern  3   b  which is an upper layer of the gate electrode  3 , a metal layer formed of W or TiN, and a silicide layer formed of TiSi 2 , CoSi 2  or NiSi 2 , etc. are generally used. 
     FIG. 1B illustrates another example of the conventional semiconductor device. Namely, the structure of the semiconductor device of FIG. 1B is the same as in FIG. 1A, except that the gate electrode  3  includes a polysilicon layer pattern  3   a , a dopant diffusion barrier layer  3   c  and a metallic film pattern  3   b . The dopant diffusion barrier layer  3   c  is formed of three components containing TiN or WNx, or TiN or WNx itself . The dopant diffusion barrier layer is hereinafter called as a barrier layer. 
     FIG. 1C illustrates yet another example of the conventional semiconductor device which includes a single metallic layer  3  as a gate electrode. 
     However, the above-described known semiconductor devices have the following problems. 
     In the above-described semiconductor devices, as shown in FIG. 1A and 1B, when the gate electrode  3  has the multilayer film structure in which the polysilicon layer  3   a  is deposited on the gate oxide film  2  and the metallic film pattern  3   b  is formed thereon, the threshold voltage Vt of the semiconductor device is determined based on the work function of the polysilicon and the doping concentration of the channel region, the metallic film pattern decreasing the resistance of the gate electrode. 
     However, in such semiconductor devices having the gate electrode which is the same as above, when the doping of the polysilicon layer is not sufficiently achieved, as the size of the semiconductor device and the power supply voltage decrease, a depletion layer is formed adjacent to the interface between the polysilicon and the gate insulation film, which results in deterioration of the current driving force of the semiconductor device, for example increase in Vt, in condition that the surface of the semiconductor substrate is in an inversion mode, namely, when a channel is formed. 
     In addition, in the polysilicon layer gate electrode, since the gate electrode of the n-channel transistor must be doped with the n-type impurity while the gate electrode of the p-channel transistor must be doped with the p-type impurity, the gate electrodes of the n-channel transistor and the p-channel transistor should be separately fabricated. 
     In addition, another problem may occur when using only the metallic film as the gate electrode. Specifically, the stress applied to the gate oxide film in which metallic layers of the gate electrode have different thermal expansion coefficients from each other is higher than the stress applied to the polysilicon during the heat treatment process which is performed by a predetermined number during the semiconductor fabrication, which results in decrease in the breakdown voltage, and deterioration of properties of the gate oxide film such as leakage current from the gate electrode. 
     Furthermore, during the etching process for forming a metallic gate electrode, the gate oxide film may be damaged, thereby degrading the characteristics of the semiconductor device. 
     Thus, when using the polysilicon layer as the gate electrode, the gate depletion occurs, and also when using the metallic film as the gate electrode, the characteristic of the semiconductor device are degraded due to the short channel effect and the damage of the gate oxide film. 
     SUMMARY OF THE INVENTION 
     The present invention is directed to a system that substantially obviates one or more of the problems experienced due to the above and other limitations and disadvantages of the related art. 
     An object of the present invention is to provide a semiconductor device and a wiring therefor and a fabrication method thereof which are capable of providing an excellent current driving capability without degrading the characteristics of the semiconductor device by making up for the problems encountered in the conventional art. 
     Another object of the present invention is to provide a semiconductor device and a wiring therefor and a fabrication method thereof in which at least two films having different material from each other are arranged in a horizontal direction. 
     Another object of the present invention is to provide a semiconductor device and a wiring therefor and a fabrication method thereof which are capable of providing a sandwich type gate electrode or a wiring which is serially formed of a first conductive film pattern/second conductive film pattern/first conductive film pattern and providing a semiconductor device which is fabricated using the above-described wiring. 
     Another object of the present invention is to provide a semiconductor device and a wiring therefor and a fabrication method thereof which are capable of providing a gate electrode or a wiring in which the first conductive film pattern is a polysilicon layer, and the second conductive film pattern is a metallic film and providing a semiconductor device fabricated using the above-described wiring. 
     Another object of the present invention is to provide a semiconductor device and a wiring therefor and a fabrication method thereof which are implemented by fabricating by one step the gate electrodes of an n-channel transistor and a p-channel transistor for thereby simplifying the fabrication process. 
     Other and further objects, features and advantages of the present invention will be set forth in the description that follows, and in part will become apparent from the detailed description, or may be learned by practice of the invention. 
     To achieve these and other advantages and in accordance with the purpose of the present invention, as embodied and broadly described, the present invention includes an insulation layer formed on the upper surface of the semiconductor substrate, and a gate electrode formed of more than two members which are serially formed on the upper surface of the insulation layer. 
     To achieve the above objects, there is provided a semiconductor device and a fabrication method thereof which includes a source/drain formed on a semiconductor substrate at both sides of a gate electrode. 
     To achieve the above objects, there is provided a wiring or gate electrode fabrication method for a semiconductor device, which includes the steps of forming a first conductive film on an upper surface of a semiconductor substrate, patterning the first insulation film, forming an opening, partially exposing the upper surface of the semiconductor substrate, and forming a first insulation film pattern, forming a second insulation film on the upper surface of the exposed semiconductor substrate, forming a pattern (sidewall spacer) in both inner walls of the opening, sequentially filling the opening with the second conductive film pattern, forming a second conductive film on the entire resultant structure of the semiconductor substrate and etching-back the same, fully filling the opening, and removing the first insulation film pattern. 
     To achieve the above objects, there is provided a fabrication method of a semiconductor device which includes the steps of forming a wiring of the semiconductor device, self-aligning the wiring of the semiconductor device and doping the surface of the semiconductor substrate at both sides of the wiring. 
     In the above wiring step of the semiconductor device, there is provided a step for partially doping the surface of the semiconductor substrate through an opening before the forming step of the second conductive film. 
     To achieve the above objects, there is provided a wiring method for a semiconductor device which includes the steps of forming a first insulation film on an upper surface of a semiconductor substrate, pattering the first insulation film and forming a first insulation film pattern and an opening, forming a second insulation film on an upper surface of the semiconductor substrate and on the opening, forming a first conductive film on the entire resultant structure of the semiconductor substrate and etching-back the same and forming a first conductive film pattern on both side walls of the first insulation film pattern, forming a second conductive film on the entire resultant structure of the semiconductor substrate, partially forming a mask pattern on the upper portion of the second conductive film, etching and patterning the second conductive film based on the mask pattern, and removing the mask pattern and the first insulation film pattern. 
     To achieve the above objects, there is provided a wiring method for a semiconductor device which includes the steps of forming a first insulation film on an upper surface of a semiconductor substrate, patterning the first insulation film and forming an opening and a first insulation film pattern, forming a second insulation film on the upper surface of the semiconductor substrate and on the opening, forming a third insulation film on the entire resultant structure of the semiconductor substrate and etching-back the same and forming a third insulation film pattern on both side walls of the first insulation film pattern, filling the first conductive film pattern into the opening which is not covered by the third insulation film pattern, and removing the third insulation film pattern and filling the second conductive film into the portion formed after removing the third insulation film pattern. 
     In the above wiring steep for the semiconductor device, there is further provided a step for doping a part of the surface of the semiconductor substrate through the opening before the formation of the first conductive film. 
     In the above wiring step for the semiconductor device, there is further provided a step for forming a barrier film on side walls of the third insulation film pattern before the formation of the first conductive film. 
     More preferably, the second insulation film which is exposed through the opening is removed before the formation of the first conductive film, and a fourth insulation film may be formed on the upper surface of the exposed semiconductor substrate. At this time, the fourth insulation film may be made of the same material as the second insulation film or it may be made of a different material. In addition, the thickness of fourth insulation film may be the same as the second insulation film or the thickness thereof may be different from that of the second insulation film. 
     In addition, after a wiring for a semiconductor device, there is further provided a step for doping the surface of the semiconductor substrate and at both sides of the wiring using the wiring for a semiconductor device as a self-aligning mask. 
     Additional advantages, objects and features of the invention will become more apparent from the description which follows. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The present invention will become more fully understood from the detailed description given hereinbelow and the accompanying drawings which are given by way of illustration only, and thus are not limitative of the present invention, and wherein: 
     FIGS. 1A through 1C are cross-sectional views illustrating the wiring and construction of a known semiconductor device; 
     FIGS. 2A through 2D are cross-sectional views illustrating the wiring and construction of a semiconductor device of the present invention; 
     FIGS. 3A through 3F are cross-sectional views illustrating a wiring and a fabrication method of a semiconductor device of FIG. 2A which shows a first embodiment of the present invention; 
     FIGS. 4A through 4E are cross-sectional views illustrating a wiring and a fabrication method of a semiconductor device of FIG. 2A according to another example of the first embodiment of the present invention; 
     FIGS. 5A through 5E are cross-sectional views illustrating a wiring and fabrication method of the semiconductor device of FIG. 2B according to yet another example of the first embodiment; 
     FIGS. 6A through 6F are cross-sectional views illustrating a wiring and a fabrication method of a semiconductor device of FIG. 2C which shows a second embodiment of the present invention; and 
     FIGS. 7A through 7D are cross-sectional views illustrating a wiring and fabrication method of the semiconductor device of FIG. 2D according to another example of the second embodiment. 
     It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory and are intended to provide further explanation of the invention as claimed. Thus, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of example only. Various changes and modifications that are within the spirit and scope of the invention will become apparent to those skilled in the art fro this detailed description. In fact, other objects, features and characteristics of the present invention; methods, operation, and functions of the related elements of the structure; combinations of parts; and economies of manufacture will surely become apparent from the following detailed description of the preferred embodiments and accompanying drawings, all of which form a part of this specification, wherein like reference numerals designate corresponding parts in various figures. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Reference will now be made in detail to the preferred embodiments of the present invention, examples of which are illustrated in the accompanying drawings. In the drawings, redundant description of like elements and processes, which are designated with like reference numerals, is omitted for brevity. 
     FIG. 2A illustrates the semiconductor device and the construction of its wiring according to a first embodiment of the present invention. As shown therein, a semiconductor substrate  11  is doped with a first conductive type impurity. When fabricating a p-type MOS transistor, the semiconductor substrate is doped by an n-type impurity. In the present invention, the n-type MOS transistor will be explained. However, although the conductive type of the impurity is contrary for a p-type MOS transistor, remaining elements are the same as the n-type MOS transistor discussed hereinafter. 
     The semiconductor substrate  11  is doped with the p-type impurity. An insulation film  12  is formed on the semiconductor substrate  11 . The insulation film  12  on the P-type impurity is an oxide film formed by a thermal oxide method and is called a gate oxide film. A wiring  13  including a first conductive film pattern  13   a , a second conductive film pattern  13   b , and another first conductive film pattern  13   a  is serially arranged on the upper surface of the insulation film  12  (gate insulation film). The wiring  13  is a gate electrode. Here, the first conductive film pattern  13   a  is a doped polysilicon layer, and the second conductive film pattern  13   b  is a metallic film. The metallic film is a metallic layer such as W or TiN or a silicide layer such as TiSi 2 , CoSi 2 , NiSi 2 , etc. 
     Next, a source/drain  14 , which is an n-type impurity layer is formed on the surface of the semiconductor substrate at both sides of the wiring or gate electrode  13 . 
     In addition, a high density p-type doping layer  11   a  is formed on the surface of a part of the semiconductor and below the insulation film  12 . The p-type doping layer  11   a  is used for controlling the threshold voltage. More preferably, the p-type doping layer  11   a  may not be formed based on the characteristic of the semiconductor device. 
     FIG. 2B illustrates a wiring of the semiconductor device according to another example of the first embodiment of the present invention. As shown therein, the construction is the same as the embodiment shown in FIG. 2A except that a barrier film  13   c  is formed between the first conductive film pattern  13   a  and the second conductive film pattern  13   b . The barrier film is made of TiN, WNx, etc. 
     FIG. 2C illustrates the construction of a semiconductor device and a wiring according to a second embodiment of the present invention. 
     As shown therein, an insulation film or gate oxide film  12  is formed on the p-type semiconductor substrate  11 , and a first conductive film pattern  23   a  is formed on an edge portion of the upper surface of the gate oxide film  12 , and a second conductive film pattern  23   b  is formed on the upper surface and lateral surface of the first conductive film pattern  23   a . Here, it is noted that the first conductive film pattern  23   a  is a polysilicon layer and the second conductive film pattern  23   b  is a metallic film. The metallic film is a metallic layer such as W or TiN, or a silicide layer such as TiSi 2 , CoSi 2 , NiSi 2 , etc. The combination of the first conductive film pattern  23   a  and the second conductive film pattern  23   b  is referred to a wiring  23  of the semiconductor device or a gate electrode  23 . A source/drain  14  doped with the n-type impurity is formed at both sides of the wiring  23  on the surface of the semiconductor substrate. 
     In addition, a high density p-type doping layer  11   a  is formed on the surface of a part of the semiconductor substrate and below the insulation film  12 . It is noted that the p-type doping layer  11   a  provided for controlling the threshold voltage can be deleted based on the characteristic of the semiconductor device. 
     FIG. 2D illustrates another example of the second embodiment of the present invention. The structure thereof is the same as the second embodiment shown in FIG. 2C except that a barrier film  23   c  of TiN, WN, etc. is formed in an interface between the first conductive film pattern  23   a  and the second conductive film pattern  23   b.    
     The fabrication method for a semiconductor device according to the present invention will now be explained with reference to the accompanying drawings. 
     FIG. 3A is a cross-sectional view illustrating a semiconductor device. As shown therein, the semiconductor substrate  11  is doped with a p-type impurity. The first insulation film  16  (not shown), a nitride film, at a thickness of 500˜2000Å is formed on the semiconductor substrate  11  doped with the p-type impurity (hereinafter called a p-type semiconductor substrate) and is patterned for thereby forming an opening  16   a  on the first insulation film  16 , so that a part of the upper surface of the semiconductor substrate  11  is exposed. The first insulation film  16  remained after the patterning is now referred to a first insulation film pattern  16   b . The first insulation film  16  is formed of a gate electrode which will be described later and a material having a high etching selection ratio. In the present invention, more preferably, the nitride film is used as a first insulation film. 
     Next, a second insulation film  12  is formed on the upper surface of the semiconductor substrate  11  which is exposed by the opening  16   a . The second insulation film  12  at a thickness of 30˜100Å is formed by the thermal oxide method thus fabricating the structure shown in FIG.  3 A. The second insulation film  12  is a gate oxide film. 
     Thereafter, the first conductive film is formed at a thickness of 500˜1500Å over the resultant structure shown in FIG. 3A before being etched back to achieve the pattern shown in FIG. 3B, the first conductive film being a doped polysilicon layer. A first conductive film sidewall spacer  13   a , namely, a first conductive film pattern, is formed on both lateral walls of the opening  16   a . The doped polysilicon layer may be formed by an in-situ process or may be formed by depositing a non-doped polysilicon layer and then doping a impurity into the polysilicon layer. 
     Next, in the structure of FIG. 3B, a p-type impurity is implanted into the portion of the surface of the semiconductor substrate  11  positioned below the second insulation film  12  and between the two portions of the first conductive pattern  13   a , thereby forming a p-type doping layer  11   a  as shown in FIG.  3 C. If the p-type doping layer  11   a  is not required due to the characteristic of the desired semiconductor device, the above process can be omitted. Since the p-type doping layer  11   a  is formed to control the threshold voltage Vth of the semiconductor device, if it is possible to obtain a desired threshold voltage by using the p-type impurity density of the semiconductor substrate  11  itself, the step of forming the p-type impurity layer  11   a  also can be omitted. 
     The second conductive film is subsequently deposited on the entire resultant structure shown in FIG.  3 C and then is etched back. The second conductive film pattern  13   b  is filled into the inner side of the first conductive film pattern  13   a  formed in an inner wall of the opening  16   a  by chemical mechanical polishing (CMP), thereby fabricating the structure shown in FIG.  3 D. Here, it is noted that the second conductive film is a metallic film, particularly, formed of W or TiN at a thickness of 2000˜4000 Å. 
     As shown in FIG. 3E, a wiring for a semiconductor device is formed, including the second conductive film pattern  13   b  formed in the center portion thereof by selectively etching the first insulation film pattern  16   b  and first conductive film patterns  13   a  formed at both sides of the second conductive film pattern  13   b . The portions of the surface of the semiconductor substrate  11  at both sides of the wiring  13  are doped by the n-type impurity to form the n-type doping layer also known as the source/drain  14 , so that the fabrication of the semiconductor device shown in FIG. 3F is completed. 
     As shown in FIG. 2B, the wiring for a semiconductor device according to another example of the first embodiment of the present invention is implemented by sequentially performing the steps of FIGS. 3A and 3B. Then, the barrier film formed of TiN or WNx is formed on the entire resultant structure shown in FIG.  3 B. Thereafter, the barrier film is etched back to form the barrier film  13   c  at the lateral wall of the first conductive film pattern  13   a , and then the steps of FIGS. 3C through 3E are sequentially performed to fabricate the wiring for the semiconductor device. 
     The structure of a semiconductor device and a wiring of FIG. 2A according to the first embodiment of the present invention can also be preferably fabricated as described hereinafter with respect to FIGS. 4A through 4F. 
     First, a first insulation film is deposited and patterned on the semiconductor substrate  11 , thereby forming an opening  16   a  and a first insulation film pattern  16   b . Here, the upper surface of the semiconductor substrate  11  is exposed through the opening  16   a . A second insulation film  12  is formed on the upper surface of the exposed semiconductor substrate  11  by the thermal oxide method. Next, a third insulation film is formed on portions of the upper surface of the first insulation film pattern  16   b  and the second insulation film  12  and then etched back, and a third insulation film pattern  17   a  (a side wall spacer) is formed at both lateral walls of the opening  16   a . The third insulation film is formed of a material, such as PSG, having a high etching selectivity to the first and second insulation film. The above-described steps are sequentially performed to fabricate a semiconductor substrate having a cross section as in FIG.  4 A. 
     During the etching-back process, when the third insulation film is removed, the portion of the second insulation film  12  positioned below the third insulation film pattern  17   a  may be removed for thereby exposing a predetermined portion of the semiconductor substrate  11 , as shown in FIG.  4 A′. In addition, as shown in FIG.  4 A″, there can be further provided a step in which a fourth insulation film  12 ′ is selectively formed on the exposed portion of the upper surface of the semiconductor substrate  11 , between the sidewall spacers  17   a  and the second insulation film  12  thereunder. Here, the fourth insulation film  12 ′ is formed by the thermal oxide method or by depositing an oxide film or a nitride film. The fourth insulation film  12 ′ may be formed of a material such as the second insulation film  12  or other different material. Further, the fourth insulation film  12 ′ is formed in accordance with characteristics of the device irrespective of the thickness of the second insulation film  12 . For example, the thickness of the insulation films  12  and  12 ′ may be adjusted such that the portion of the insulation film  12  positioned below the first conductive film pattern  17   a  is different from the thickness of the portion of the insulation film  12 ′ positioned below the second conductive film pattern  13   b . 
     Next, regardless of whether the process of FIGS.  4 A′ through  4 A″ are performed to form fourth insulation film  12 ′, a second conductive film pattern  13   b  is filled into the opening  16   a  inside the third insulation film patterns  17   a , as shown in FIG. 4B, the second conductive film pattern  13   b  being formed of a metallic film such as a metal layer or a metal silicide layer. The second conductive film pattern  13   b  is formed by depositing the second conductive film over the entire resultant structure of FIG. 4A or FIG.  4 A″ and then performing the etch-back process thereto or CMP, or some conventional process. 
     As shown in FIG. 4C, the third insulation film pattern  17   a  is selectively removed. If the third insulation film pattern  17   a  is formed of PSG, the third insulation film pattern can be removed by an HF vapor process. 
     The first conductive film pattern  13   a  is formed on the portion in which the third insulation film pattern  17   a  is removed. The first conductive film pattern  13   a  is formed of a doped polysilicon layer. The first conductive film pattern  13   a  is formed in such manner that the first conductive film, namely, the doped polysilicon layer, is formed on the entire resultant structure of FIG. 4D, and the etch-back process or CMP is applied thereto. Next, the wiring step for a semiconductor device is completed by removing the first insulation film pattern  16   b.    
     The n-type doping layer, the source/drain  14 , is formed, as shown in FIG. 4E, by implanting an n-type impurity into the surface of the semiconductor substrate and at both sides of the wiring  13  of the semiconductor device in which the first conductive film patterns  13   a  are arranged at both sides of the second conductive film pattern  13   a.    
     As shown in FIG. 5A-5E, after the steps shown in FIGS. 4A or  4 A″, there may be further provided steps to achieve the structure shown in FIG. 2B, where a barrier film is interposed between the first and second conductive film patterns. In FIG. 5A, a TiN or WNx layer is formed on the entire resultant structure shown in FIGS. 4A (or FIG.  4 A″) which is etched back before a barrier film  13 A is formed on the exposed lateral surfaces of the third insulation film pattern  17   a . The steps of FIGS. 5B through 5E are then sequentially performed similar to the steps of FIGS. 4B through 4E, so that the wiring for a semiconductor device according to another example of the first embodiment of the present invention is fabricated, which is similar to the embodiment of FIG.  2 B. 
     The wiring for a semiconductor device and a semiconductor device adapting the same according to the second embodiment of the present invention may be fabricated by sequentially performing the steps of FIGS. 6A through 6F. 
     The steps of FIGS. 6A through 6C are sequentially performed in a manner similar to the steps of FIGS. 3A through 3C. 
     Next, as shown in FIG. 6D, the second conductive film  23  is formed on the entire resultant structure of FIG.  6 C. Here, the second conductive film  23  is formed of one selected from the group comprising W or TiN and has a thickness of 2000˜4000 Å. 
     Before the formation of the second conductive film  23 , there can be further provided a step in which a TiN layer or a WNx layer is formed on the entire resultant structure of FIG.  6 C and then is etched back, and a barrier layer  13   c  (shown in FIG. 2D) is formed on both lateral walls of the first conductive film pattern  13   a.    
     After the formation of the second conductive film  23 , as shown in FIG. 6D, a mask pattern  18  having the same size as the opening  16   a  is formed on the upper surface of the second conductive film  23  and in the portion of the opening  16   a  shown in FIG.  6 A. Thereafter, the second conductive film  23  is etched using the mask pattern  18 , and then the second conductive pattern  23   b  shown in FIG. 6E is formed. 
     As shown in FIGS. 6E through 6F, the second insulation film pattern  16   b  is selectively etched. 
     An n-type impurity is doped on the surface of the semiconductor substrate  11  and at both sides of the wiring  23  to form source/drain regions  14 , and then the fabrication of the semiconductor device is finished. 
     As shown in FIGS. 7A through 7D, after the step shown in FIG. 6B, there may be further provided steps to achieve the structure shown in FIG. 2D, in which a barrier film is interposed between the first and second conductive film patterns  23   a ,  23   b . In FIG. 7A, a TiN or WNx layer is formed on the entire resultant structure shown in FIG. 6A which is etched back before barrier layer  23   c  is formed on the exposed surfaces of the first conductive film pattern  23   a . Thereafter, in the step shown in FIG. 7B, second conductive film  23   b  is formed on barrier layer  23   c  and first insulation film pattern  16   b , and the subsequent steps of FIGS. 7B through 7D are performed like those of FIGS. 6D through 6F, respectively. 
     As described above, in the present invention, it is possible to decrease the wiring resistance by arranging the metallic film on the center portion of the wiring and the characteristic of the device such as a current driving capability of the semiconductor device is enhanced by preventing the gate depletion phenomenon. In addition, a buried channel phenomenon is prevented by arranging the polysilicon layer pattern at both edge portions of the metallic film for thereby enhancing the characteristic of the semiconductor device. 
     In addition, in the present invention, the metallic film is used as a part of the gate electrode. When fabricating the CMOS transistor, the NMOS transistor gate electrode and the PMOS transistor gate electrode may be simultaneously fabricated using the above described processes; they need not be individually fabricated. Therefore, the fabrication process of the semiconductor device is simplified, so that the productivity of the semiconductor device is increased. While there have been illustrated and described what are at present considered to be preferred embodiments of the present invention, it will be understood by those skilled in the art that various changes and modifications may be made, and equivalents may be substituted for elements thereof without departing from the true scope of the present invention. In addition, many modifications may be made to adapt a particular situation or material to the teaching of the present invention without departing from the central scope thereof. Therefor, it is intended that the present invention not be limited to the particular embodiment disclosed as the best mode contemplated for carrying out the present invention, but that the present invention includes all embodiments falling within the scope of the appended claims. 
     The foregoing description and the drawings are regards as including a variety of individually inventive concepts, some of which may lie partially or wholly outside the scope of some or all of the following claims. The fact that the applicant has chosen at the time of filing of the present application to restrict the claimed scope of protection in accordance with the following claims is not to be taken as a disclaimer of alternative inventive concepts that are included in the contents of the application and could be defined by claims differing in scope from the following claims, which different claims may be adopted subsequently during prosecution, for example, for the purposes of a continuation or divisional application.