Abstract:
Provided is a metal-oxide semiconductor (MOS) transistor containing a metal gate pattern. The semiconductor device includes a p-channel metal-oxide semiconductor (PMOS) transistor including a semiconductor substrate, a first insulating film formed on the semiconductor substrate, a first metal gate conductive film formed on the first insulating film, and a nitrogen diffusion blocking film formed between the first insulating film and the first metal gate conductive film, and an n-channel metal-oxide semiconductor (NMOS) transistor including the semiconductor substrate, a second insulating film formed on the semiconductor substrate, a second metal gate conductive film formed on the second insulating film, and a reaction blocking film formed of metal nitride and formed between the second insulating film and the second metal gate conductive film. According to the inventive concept, a reaction between a metal gate film and an insulating film may be minimized so as to result in a highly reliable MOS transistor.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
       [0001]    This application claims the benefit of Korean Patent Application No. 10-2009-0018911, filed on Mar. 5, 2009, in the Korean Intellectual Property Office, the disclosure of which is incorporated herein in its entirety by reference. 
       BACKGROUND 
       [0002]    The inventive concept relates to a semiconductor device, and more particularly, to a metal-oxide semiconductor (MOS) transistor containing a metal gate pattern. 
         [0003]    To improve the reliability of transistors in an integrated circuit, research has been conducted to increase the operating speed and functionality of a semiconductor device and also decrease the power consumption thereof. 
       SUMMARY 
       [0004]    The inventive concept provides a semiconductor device including a metal-oxide semiconductor (MOS) transistor having excellent reliability. 
         [0005]    According to an aspect of the inventive concept, there is provided a semiconductor device comprising p-channel metal-oxide semiconductor (PMOS) and n-channel metal-oxide semiconductor (NMOS) transistors. 
         [0006]    The PMOS transistor may include a semiconductor substrate, a first insulating film formed on the semiconductor substrate, a first metal gate conductive film formed on the first insulating film, and a nitrogen diffusion blocking film formed between the first insulating film and the first metal gate conductive film. The NMOS transistor may include the semiconductor substrate, a second insulating film formed on the semiconductor substrate, a second metal gate conductive film formed on the second insulating film, and a reaction blocking film formed of metal nitride and formed between the second insulating film and the second metal gate conductive film. The metal nitride may be nitrogen-rich metal nitride in which the content of nitrogen is greater than the content of stoichiometric nitrogen. The first and second insulating films may include one selected from the group consisting of silicon oxide (SiO 2 ), silicon oxynitride (SiO x1 N y1 ), hafnium oxide (HfO 2 ), hafnium oxynitride (HfO x2 N y2 ), hafnium silicon oxide (HfSi x3 O y3 ), hafnium silicon oxynitride (HfSi x4 O y4 N z4 ), zirconium oxide (ZrO 2 ), zirconium oxynitride (ZrO x5 N y5 ), zirconium silicon oxide (ZrSi x6 O y6 ), zirconium silicon oxynitride (ZrSi x7 O y7 N z7 ), tantalum oxide (Ta 2 O 5 ), tantalum oxynitride (TaO x8 N y8 ), tantalum silicon oxide (TaSi x9 O y9 ), tantalum silicon oxynitride (TaSi x10 O y10 N z10 ), aluminum oxide (Al 2 O 3 ), aluminum oxynitride (AlO x11 N y11 ), aluminum silicon oxide (AlSi x12 O y12 ), aluminum silicon oxynitride (AlSi x13 O y13 N z13 ), titanium oxide (TiO 2 ), titanium oxynitride (TiO x14 N y14 ), titanium silicon oxide (TiSi x15 O y15 ), titanium silicon oxynitride (TiSi x16 O y16 N z16 ), and combinations thereof, wherein the subscripts “x1” to “z16” indicate any positive real number, respectively. 
         [0007]    The nitrogen diffusion blocking film may include metal carbide or nitrogen-free metal. In particular, the metal carbide or the nitrogen-free metal may include titanium (Ti), tantalum (Ta), titanium silicide (TiSi), or tantalum silicide (TaSi). 
         [0008]    The nitrogen-rich metal nitride may include Ti or Ta. 
         [0009]    The semiconductor device may further include a capping layer formed directly on or under the first and second insulating films, wherein the capping layer is an oxide film comprising lanthanum (La), aluminum (Al), or magnesium (Mg). 
         [0010]    The semiconductor substrate under the first and second insulating films may include silicon carbide (SiC) or silicon germanium (SiGe). 
         [0011]    The first and second metal gate conductive films may include the same material or different materials. For example, the first and second metal gate conductive films may include one selected from the group consisting of tantalum (Ta), titanium (Ti), titanium nitride (TiN), tungsten (W), nickel (Ni), tantalum silicon (TaSi), tungsten silicon (WSi), titanium silicon (TiSi), molybdenum silicon (MoSi), nickel silicon (NiSi), ruthenium (Ru), ruthenium oxide (RuO), iridium (Ir), iridium oxide (IrO), and platinum (Pt). 
         [0012]    The PMOS transistor may further comprise the reaction blocking film formed between the nitrogen diffusion blocking film and the first metal gate conductive film. The reaction blocking film of the PMOS transistor may be positioned higher on the semiconductor substrate than the reaction blocking film of the NMOS transistor. 
         [0013]    According to an aspect of the inventive concept, a p-channel metal-oxide semiconductor (PMOS) transistor comprises a semiconductor substrate, a gate insulating film formed on the semiconductor substrate, a metal gate conductive film formed on the gate insulating film, and a nitrogen diffusion blocking film formed between the gate insulating film and the metal gate conductive film. 
         [0014]    The nitrogen diffusion blocking film may comprise metal carbide or nitrogen-free metal. The metal carbide or the nitrogen-free metal may comprise titanium (Ti), tantalum (Ta), titanium silicide (TiSi), or tantalum silicide (TaSi). 
         [0015]    The PMOS transistor may further comprises a reaction blocking film formed of metal nitride and formed between the nitrogen diffusion blocking film and the metal gate conductive film. 
         [0016]    According to an aspect of the inventive concept, an n-channel metal-oxide semiconductor (NMOS) transistor comprises, a semiconductor substrate, a gate insulating film formed on the semiconductor substrate, a metal gate conductive film formed on the gate insulating film, and a reaction blocking film formed of metal nitride and formed between the gate insulating film and the metal gate conductive film. 
         [0017]    The metal nitride may be nitrogen-rich metal nitride in which the content of nitrogen is greater than the content of stoichiometric nitrogen, and may comprise Ti or Ta. 
         [0018]    According to the inventive concept, a reaction between a metal gate film and an insulating film may be minimized so as to realize a highly reliable MOS transistor. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0019]    Exemplary embodiments of the inventive concept will be more clearly understood from the following detailed description taken in conjunction with the accompanying drawings in which: 
           [0020]      FIG. 1  is a cross-sectional diagram of a gate of a conventional p-channel metal-oxide semiconductor (PMOS) transistor; 
           [0021]      FIG. 2  is a cross-sectional diagram of a gate according to an embodiment of the inventive concept; 
           [0022]      FIG. 3  is a cross-sectional diagram of a gate of a conventional n-channel metal-oxide semiconductor (NMOS) transistor; 
           [0023]      FIG. 4  is a cross-sectional diagram of a gate according to an embodiment of the inventive concept; and 
           [0024]      FIGS. 5 through 9  are cross-sectional diagrams for describing a method of forming a semiconductor device according to an embodiment of the inventive concept. 
       
    
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS 
       [0025]    Reference will now be made in more detail to exemplary embodiments, examples of which are illustrated in the accompanying drawings. However, the inventive concept is not limited to the embodiments illustrated hereinafter, and the embodiments herein are introduced in an effort to provide a complete understanding of the scope and spirit of the inventive concept. In the drawings, the thicknesses of layers and regions may be exaggerated for clarity. 
         [0026]    It will be understood that when an element, such as a layer, a region, or a substrate, is referred to as being “on”, “connected to” or “coupled to” another element, it may be directly on, connected or coupled to the other element or intervening elements may be present. Like reference numerals may refer to like elements throughout. 
         [0027]      FIG. 1  is a cross-sectional diagram of a gate of a conventional p-channel metal-oxide semiconductor (PMOS) transistor. 
         [0028]    Referring to  FIG. 1 , a gate insulating film  12  is formed on a semiconductor substrate  11  and then a gate conductive film  16  is formed on the gate insulating film  12 . The gate insulating film  12  should maintain a thin equivalent oxide film thickness and sufficiently reduce a leakage current between channel regions of the gate conductive film  16  and the semiconductor substrate  11 . Thus, metal oxide having a high permittivity is mostly used to form the gate insulating film  12 . Also, in some cases, metal oxynitride having a high permittivity may be used. 
         [0029]    The gate conductive film  16  may be a metal-containing film. The gate conductive film  16  may be formed by using a physical vapor deposition (PVD) method, a chemical vapor deposition (CVD) method, or an atomic layer deposition (ALD) method. A nitrogen gas may be used as a reaction gas or a carrier gas in the PVD method, the CVD method, or the ALD method or may be contained in a process atmosphere for manufacturing a semiconductor device. 
         [0030]    Thus, in most cases, nitrogen atoms and/or molecules  20  are contained in the gate conductive film  16 . In a following process performed at high temperature, the nitrogen atoms and/or molecules  20  may be diffused into the gate insulating film  12  and thus the gate insulating film  12  may react with the nitrogen atoms and/or molecules  20 . Due to the reaction, an interface trap may occur and fixed oxide charges may also occur. 
         [0031]    Such a phenomenon may be a main cause of negative bias temperature instability (NBTI) deterioration of a PMOS transistor. In general, if a negative bias is applied to a gate of a transistor while increasing a temperature of the transistor, in order to perform a stress test of a semiconductor device, an NBTI phenomenon occurs in the transistor and thus the electrical characteristics of the semiconductor device deteriorate. The NBTI phenomenon is caused by a hole trap at an interface between a Si film and a gate insulating film in an active region when a semiconductor device operates. In particular, a variation range of a threshold voltage Vth due to NBTI deterioration is increased in a PMOS transistor more than in an n-channel metal-oxide semiconductor (NMOS) transistor. 
         [0032]      FIG. 2  is a cross-sectional diagram of a gate, for example, of a p-channel metal-oxide semiconductor (PMOS) transistor, according to an embodiment of the inventive concept. 
         [0033]    Referring to  FIG. 2 , a gate insulating film  120  is formed on a semiconductor substrate  110  and then a gate conductive film  160  is formed on the gate insulating film  120 . A nitrogen diffusion blocking film  140  is formed between the gate insulating film  120  and the gate conductive film  160 . 
         [0034]    Examples of the semiconductor substrate  110  include a silicon (Si) substrate, a silicon-on-insulator (SOI) substrate, a germanium (Ge) substrate, a germanium -on-insulator (GOI) substrate, and an Si-Ge substrate. 
         [0035]    The gate insulating film  120  should maintain a thin equivalent oxide film thickness and sufficiently reduce a leakage current between channel regions of the gate conductive film  160  and the semiconductor substrate  110 . Thus, metal oxide having a high permittivity is mostly used to form the gate insulating film  120 . Also, in some cases, metal oxynitride having a high permittivity may be used. Examples of a material for forming the gate insulating film  120  include silicon oxide (SiO 2 ), silicon oxynitride (SiO x1 N y1 ), hafnium oxide (HfO 2 ), hafnium oxynitride (HfO x2 N y2 ), hafnium silicon oxide (HfSi x3 O y3 ), hafnium silicon oxynitride (HfSi x4 O y4 N z4 ), zirconium oxide (ZrO 2 ), zirconium oxynitride (ZrO x5 N y5 ), zirconium silicon oxide (ZrSi x6 O y6 ), zirconium silicon oxynitride (ZrSi x7 O y7 N z7 ), tantalum oxide (Ta 2 O 5 ), tantalum oxynitride (TaO x8 N y8 ), tantalum silicon oxide (TaSi x9 O y9 ), tantalum silicon oxynitride (TaSi x10 O y10 N z10 ), aluminum oxide (Al 2 O 3 ), aluminum oxynitride (AlO x11 N y11 ), aluminum silicon oxide (AlSi x12 O y12 ), aluminum silicon oxynitride (AlSi x13 O y13 N z13 ), titanium oxide (TiO 2 ), titanium oxynitride (TiO x14 N y14 ), titanium silicon oxide (TiSi x15 O y15 ), titanium silicon oxynitride (TiSi x16 O y16 N z16 ), and combinations thereof, wherein the subscripts “x1” to “z16” indicate any positive real number, respectively. 
         [0036]    The gate conductive film  160  may be a metal-containing film, and may contain one selected from the group consisting of, for example, tantalum (Ta), titanium (Ti), titanium nitride (TiN), tungsten (W), nickel (Ni), tantalum silicon (TaSi), tungsten silicon (WSi), titanium silicon (TiSi), molybdenum silicon (MoSi), nickel silicon (NiSi), ruthenium (Ru), ruthenium oxide (RuO), iridium (Ir), iridium oxide (IrO), and platinum (Pt). 
         [0037]    The nitrogen diffusion blocking film  140  formed between the gate conductive film  160  and the gate insulating film  120  prevents nitrogen atoms and/or molecules  20  contained in the gate conductive film  160  from being diffused into the gate insulating film  120 . The nitrogen diffusion blocking film  140  may be formed of metal carbide or nitrogen-free pure metal. For example, the metal carbide or the nitrogen-free pure metal may contain a Ti-based material, a Ta-based material, a titanium silicide (TiSi m )-based material, or a tantalum silicide (TaSi n )-based material, wherein the subscripts “m” and “n” indicate any positive real number, respectively. 
         [0038]    Thus, since the nitrogen diffusion blocking film  140  is disposed between the gate conductive film  160  and the gate insulating film  120 , the increase in a variation range of a threshold voltage Vth due to NBTI deterioration may be prevented. In particular, such improvement is greater in a PMOS transistor than in an NMOS transistor. 
         [0039]      FIG. 3  is a cross-sectional diagram of a gate of a conventional NMOS transistor. 
         [0040]    Referring to  FIG. 3 , a gate insulating film  22  is formed on a semiconductor substrate  21  and then a gate conductive film  26  is formed on the gate insulating film  22 . The gate insulating film  22  should maintain a thin equivalent oxide film thickness and sufficiently reduce a leakage current between channel regions of the gate conductive film  26  and the semiconductor substrate  21 . Thus, metal oxide having a high permittivity is mostly used to form the gate insulating film  21 . Also, in some cases, metal oxynitride having a high permittivity may be used. The gate conductive film  26  may be a metal-containing film. If the gate conductive film  26  contains metal, a reaction layer  23  may be formed on an interface between the gate conductive film  26  and the gate insulating film  22  due to reaction with the gate insulating film  22 . As such, an oxygen vacancy in the gate insulating film  22  is increased. Thus, a trap site may occur in the gate insulating film  22  and fixed oxide charges may also occur. 
         [0041]    Such a phenomenon may be a cause of a positive bias temperature instability (PBTI) deterioration of an NMOS transistor. In general, if a positive bias is applied to a gate of a transistor while increasing a temperature of the transistor, in order to perform a stress test of a semiconductor device, a PBTI phenomenon occurs in the transistor and thus the electrical characteristics of the semiconductor device deteriorate. 
         [0042]      FIG. 4  is a cross-sectional diagram of a gate, for example, of an NMOS transistor, according to an embodiment of the inventive concept. 
         [0043]    Referring to  FIG. 4 , a gate insulating film  220  is formed on a semiconductor substrate  210  and then a gate conductive film  260  is formed on the gate insulating film  220 . Meanwhile, a reaction blocking film  240  is formed between the gate insulating film  220  and the gate conductive film  260 . 
         [0044]    Examples of the semiconductor substrate  210  include an Si substrate, an SOI substrate, a Ge substrate, a GOI substrate, and an Si—Ge substrate. 
         [0045]    The gate insulating film  220  should maintain a thin equivalent oxide film thickness and sufficiently reduce a leakage current between channel regions of the gate conductive film  260  and the semiconductor substrate  210 . Thus, metal oxide having a high permittivity is mostly used to form the gate insulating film  220 . Also, in some cases, metal oxynitride having a high permittivity may be used. Examples of a material for forming the gate insulating film  220  include silicon oxide (SiO 2 ), silicon oxynitride (SiO x1 N y1 ), hafnium oxide (HfO 2 ), hafnium oxynitride (HfO x2 N y2 ), hafnium silicon oxide (HfSi x3 O y3 ), hafnium silicon oxynitride (HfSi x4 O y4 N z4 ), zirconium oxide (ZrO 2 ), zirconium oxynitride (ZrO x5 N y5 ), zirconium silicon oxide (ZrSi x6 O y6 ), zirconium silicon oxynitride (ZrSi x7 O y7 N z7 ), tantalum oxide (Ta 2 O 5 ), tantalum oxynitride (TaO x8 N y8 ), tantalum silicon oxide (TaSi x9 O y9 ), tantalum silicon oxynitride (TaSi x10 O y10 N z10 ), aluminum oxide (Al 2 O 3 ), aluminum oxynitride (AlO x11 N y11 ), aluminum silicon oxide (AlSi x12 O y12 ), aluminum silicon oxynitride (AlSi x13 O y13 N z13 ), titanium oxide (TiO 2 ), titanium oxynitride (TiO x14 N y14 ), titanium silicon oxide (TiSi x15 O y15 ), titanium silicon oxynitride (TiSi x16 O y16 N z16 ), and combinations thereof, wherein the subscripts “x1” to “z16” indicate any positive real number, respectively. 
         [0046]    The gate conductive film  260  may be a metal-containing film, and may contain one selected from the group consisting of for example, Ta, Ti, TiN, W, Ni, TaSi, WSi, TiSi, MoSi, NiSi, Ru, RuO, Ir, IrO, and Pt. 
         [0047]    The reaction blocking film  240  formed between the gate conductive film  260  and the gate insulating film  220  may be formed of metal nitride. The metal nitride may be nitrogen-rich metal nitride in which the content of nitrogen is greater than the content of stoichiometric nitrogen. In this case, “stoichiometric” may be understood as including a general (thermodynamically stable) quantitative correlation between metal and nitrogen in a compound formed of metal and nitrogen. 
         [0048]    For example, if the metal is Ti, the stoichiometric metal nitride is TiN. However, in nitrogen-rich titanium nitride (TiN x ), in which the content of nitrogen is greater than the content of stoichiometric nitrogen, x is greater than 1. Alternatively, if the metal is Ta, the stoichiometric metal nitride is tantalum nitride (TaN). However, in nitrogen-rich tantalum nitride (TaN y ), in which the content of nitrogen is greater than the content of stoichiometric nitrogen, y is greater than 1. 
         [0049]    Since the reaction blocking film  240  is disposed between the gate conductive film  260  and the gate insulating film  220 , the effects of PBTI deterioration may be prevented. In particular, such improvement is greater in an NMOS transistor than in a PMOS transistor. 
         [0050]      FIGS. 5 through 9  are cross-sectional diagrams for sequentially describing a method of forming a semiconductor device according to an embodiment of the inventive concept. 
         [0051]    Referring to  FIG. 5 , a gate insulating film  320  is formed on a semiconductor substrate  310 . The semiconductor substrate  310  may include an NMOS region on which an NMOS transistor is to be formed and a PMOS region on which a PMOS transistor is to be formed. The NMOS and PMOS regions may be isolated from each other by a device isolation film  315 . Hereinafter, it is assumed that the NMOS region is formed at a left side of the device isolation film  315  and the PMOS region is formed at a right side of the device isolation film  315 . 
         [0052]    Examples of the semiconductor substrate  310  include an Si substrate, an SOI substrate, a Ge substrate, a GOI substrate, and an Si-Ge substrate. A gate channel may contain silicon carbide (SiC) or silicon germanium (SiGe) in order to control a bandgap of the gate channel or to improve mobility of the gate channel. Also, nitrogen (N) ion injection and/or fluorine (F) ion injection may be performed in order to control a threshold voltage Vth of the gate channel. 
         [0053]    The gate insulating film  320  should maintain a thin equivalent oxide film thickness and sufficiently reduce a leakage current between channel regions of a gate conductive film  360   a,    360   b  (in  FIG. 9 ) and the semiconductor substrate  310 . Thus, metal oxide having a high permittivity is mostly used to form the gate insulating film  320 . Also, in some cases, metal oxynitride having a high permittivity may be used. Examples of a material for forming the gate insulating film  320  include silicon oxide (SiO 2 ), silicon oxynitride (SiO x1 N y1 ), hafnium oxide (HfO 2 ), hafnium oxynitride (HfO x2 N y2 ), hafnium silicon oxide (HfSi x3 O y3 ), hafnium silicon oxynitride (HfSi x4 O y4 N z4 ), zirconium oxide (ZrO 2 ), zirconium oxynitride (ZrO x5 N y5 ), zirconium silicon oxide (ZrSi x6 O y6 ), zirconium silicon oxynitride (ZrSi x7 O y7 N z7 ), tantalum oxide (Ta 2 O 5 ), tantalum oxynitride (TaO x8 N y8 ), tantalum silicon oxide (TaSi x9 O y9 ), tantalum silicon oxynitride (TaSi x10 O y10 N z10 ), aluminum oxide (Al 2 O 3 ), aluminum oxynitride (AlO x11 N y11 ), aluminum silicon oxide (AlSi x12 O y12 ), aluminum silicon oxynitride (AlSi x13 O y13 N z13 ), titanium oxide (TiO 2 ), titanium oxynitride (TiO x14 N y14 ), titanium silicon oxide (TiSi x15 O y15 ), titanium silicon oxynitride (TiSi x16 O y16 N z16 ), and combinations thereof, wherein the subscripts “x1” to “z16” indicate any positive real number, respectively. 
         [0054]    A nitrogen diffusion blocking film  341  is formed on a whole surface of the gate insulating film  320  including the NMOS and PMOS regions. The nitrogen diffusion blocking film  341  prevents nitrogen atoms and/or molecules contained in the gate conductive film  360   a,    360   b  (in  FIG. 9 ) from being diffused into the gate insulating film  320 . The nitrogen diffusion blocking film  341  may be formed of, for example, metal carbide or nitrogen-free pure metal. For example, the metal carbide or the nitrogen-free pure metal may contain a Ti-based material, a Ta-based material, a titanium silicide (TiSi m )-based material, or a tantalum silicide (TaSi n )-based material, wherein the subscripts “m” and “n” indicate any positive real number, respectively. The gate insulating film  320  may be formed of, for example, a hafnium silicon oxide (HfSiO)-based material. 
         [0055]    Referring to  FIG. 6 , a photoresist pattern  350  is formed on the nitrogen diffusion blocking film  341  to cover the PMOS region, and then an exposed portion of the nitrogen diffusion blocking film  341  is etched by using the photoresist pattern  350  as a mask, thereby forming a nitrogen diffusion blocking film pattern  341   a  only on the PMOS region. 
         [0056]    Referring to  FIG. 7 , a reaction blocking film  342  is formed on a whole surface of a structure formed on the semiconductor substrate  310  including the PMOS and NMOS regions. The reaction blocking film  342  may be formed of metal nitride. The metal nitride may be nitrogen-rich metal nitride in which the content of nitrogen is greater than the content of stoichiometric nitrogen. 
         [0057]    For example, if the metal is Ti, the stoichiometric metal nitride is TiN. However, in nitrogen-rich titanium nitride (TiNx), in which the content of nitrogen is greater than the content of stoichiometric nitrogen, x is greater than 1. Alternatively, if the metal is Ta, the stoichiometric metal nitride is TaN. However, in nitrogen-rich tantalum nitride (TaNx), in which the content of nitrogen is greater than the content of stoichiometric nitrogen, x is greater than 1. 
         [0058]    Due to the nitrogen diffusion blocking film pattern  341   a,  the reaction blocking film  342  may be formed to be higher on the PMOS region than on the NMOS region. 
         [0059]    Referring to  FIG. 8 , a gate conductive film (not shown) is formed on a whole surface of the reaction blocking film  342 . The gate conductive film may be a metal-containing film, and may contain one selected from the group consisting of, for example, Ta, Ti, TiN, W, Ni, TaSi, WSi, TiSi, MoSi, NiSi, Ru, RuO, Ir, IrO, and Pt. 
         [0060]    Continuously, a gate pattern structure is formed by patterning the gate insulating film  320 , the nitrogen diffusion blocking film pattern  341   a,  the reaction blocking film  342 , and the gate conductive film, which are formed on the semiconductor substrate  310 . Thus, a gate insulating film pattern  320   a,  a reaction blocking film pattern  342   a,  and a gate conductive film pattern  360   a  are formed on the NMOS region, and the gate insulating film pattern  320   a,  the nitrogen diffusion blocking film pattern  341   a,  the reaction blocking film pattern  342   a,  and the gate conductive film pattern  360   a  are formed on the PMOS region. 
         [0061]    Although the gate conductive film patterns  360   a  on the NMOS and PMOS regions are formed of the same material in  FIG. 8 , as illustrated in  FIG. 9 , the gate conductive film pattern  360   a  on the NMOS region and a gate conductive film pattern  360   b  on the PMOS region may be formed of different materials. 
         [0062]    Although not shown in  FIGS. 8 and 9 , a capping layer may further be formed directly on or under the gate insulating film  320  and may be an oxide film containing, for example, lanthanum (La), aluminum (Al), or magnesium (Mg). 
         [0063]    While the inventive concept has been particularly shown and described with reference to exemplary embodiments thereof, it will be understood that various changes in form and details may be made therein without departing from the spirit and scope of the inventive concept as illustrated in the following claims.