Abstract:
A semiconductor device having a small parasitic resistance and a high driving current is provided. The semiconductor device includes a fin portion that includes a pair of source/drain regions located on both end sides and a channel region sandwiched between the pair of source/drain regions; films that are formed on both sides in a channel-width direction of the fin portion; a gate electrode that is provided so as to stride across the channel region of the fin portion; a gate insulating film that is interposed between the gate electrode and the channel region; and a stress applying layer that applies a stress to the channel region of the fin portion, an upper surface and side surfaces of the source/drain region being coated with the stress applying layer in the fin portion, a lower end surface of the stress applying layer being in contact with the film with no gap.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application is based upon and claims benefit of priority from prior Japanese Patent Application No. 2009-33945, filed on Feb. 17, 2009, the entire contents of which are incorporated herein by reference. 
       BACKGROUND OF THE INVENTION 
       [0002]    1. Field of the Invention 
         [0003]    The present invention relates to a semiconductor device and a producing method thereof, particularly to a FinFET to which a strained silicon technique is applied and a producing method thereof. 
         [0004]    2. Background Art 
         [0005]    Recently the influence of various parasitic effects such as a parasitic resistance, a parasitic capacitance, and a short channel effect is growing with the progress of integration of the semiconductor device. A Fin Field Effect Transistor (hereinafter also referred to as FinFET) is actively developed in order to realize the semiconductor device that can suppress the parasitic effects (for example, see Japanese Patent Application Laid-Open No. 2005-294789). 
       SUMMARY OF THE INVENTION 
       [0006]    According to a first aspect of the invention, a semiconductor device includes a fin portion that includes a pair of source/drain regions located on both end sides and a channel region sandwiched between the pair of source/drain regions; 
         [0007]    films that are formed on both sides in a channel-width direction of the fin portion; a gate electrode that is provided so as to stride across the channel region of the fin portion; a gate insulating film that is interposed between the gate electrode and the channel region; and a stress applying layer that applies a stress to the channel region of the fin portion, an upper surface and side surfaces of the source/drain region being coated with the stress applying layer in the fin portion, a lower end surface of the stress applying layer being in contact with the film with no gap. 
         [0008]    According to a second aspect of the invention, a semiconductor device producing method includes preparing a silicon substrate; depositing sequentially a first mask material and a second mask material on the silicon substrate; patterning the first mask material and the second mask material; forming a substrate main body and a fin portion by etching the silicon substrate from a surface to a predetermined depth with the patterned second mask material as a mask, the fin portion being formed on the substrate main body while formed integrally with the substrate main body, the fin portion including a pair of source/drain regions located on both end sides and a channel region sandwiched between the pair of source/drain regions; depositing silicon oxide on the substrate main body, the fin portion, and the second mask material; forming an element isolation insulating film on the substrate main body by etching the silicon oxide to a predetermined thickness with the second mask material as a mask; depositing a silicon nitride film or silicon carbide nitride film on the element isolation insulating film, the fin portion, and the second mask material; forming a film on the element isolation insulating film by etching the silicon nitride or the silicon carbide nitride film to a predetermined thickness with the first mask material as a mask; forming a gate insulating film on the fin portion; forming a gate electrode that sandwiches the channel region of the fin portion, the gate insulating film being interposed between the gate electrode and the channel region; and forming a stress applying layer such that an upper surface and both side surfaces of the source/drain region of the fin portion are coated with the stress applying layer, the stress applying layer being in contact with the film with no gap, the stress applying layer being made of silicon germanium or silicon carbide. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0009]      FIG. 1A  is a perspective view illustrating FinFET according to a first embodiment of the invention; 
           [0010]      FIG. 1B  is a top view illustrating FinFET of the first embodiment; 
           [0011]      FIG. 1C  is a sectional view taken along a line A-A′ of  FIG. 1B ; 
           [0012]      FIG. 2A  is a sectional view illustrating a process for producing FinFET of the first embodiment; 
           [0013]      FIG. 2B  is a sectional view following  FIG. 2A  illustrating the process for producing FinFET of the first embodiment; 
           [0014]      FIG. 2C  is a sectional view following  FIG. 2B  illustrating the process for producing FinFET of the first embodiment; 
           [0015]      FIG. 2D  is a sectional view following  FIG. 2C  illustrating the process for producing FinFET of the first embodiment; 
           [0016]      FIG. 2E  is a sectional view following  FIG. 2D  illustrating the process for producing FinFET of the first embodiment; 
           [0017]      FIG. 2F  is a sectional view following  FIG. 2E  illustrating the process for producing FinFET of the first embodiment; 
           [0018]      FIG. 2G  is a sectional view following  FIG. 2F  illustrating the process for producing FinFET of the first embodiment; 
           [0019]      FIG. 2H  is a sectional view following  FIG. 2G  illustrating the process for producing FinFET of the first embodiment; 
           [0020]      FIG. 3A  is a perspective view illustrating FinFET according to a second embodiment of the invention; 
           [0021]      FIG. 3B  is a top view illustrating FinFET of the second embodiment; 
           [0022]      FIG. 3C  is a sectional view taken along a line A-A′ of  FIG. 3B ; 
           [0023]      FIG. 4A  is a sectional view illustrating a process for producing FinFET of the second embodiment; 
           [0024]      FIG. 4B  is a sectional view following  FIG. 4A  illustrating the process for producing FinFET of the second embodiment; 
           [0025]      FIG. 4C  is a sectional view following  FIG. 4B  illustrating the process for producing FinFET of the second embodiment; 
           [0026]      FIG. 4D  is a sectional view following  FIG. 4C  illustrating the process for producing FinFET of the second embodiment; 
           [0027]      FIG. 4E  is a sectional view following  FIG. 4D  illustrating the process for producing FinFET of the second embodiment; 
           [0028]      FIG. 5A  is a perspective view illustrating FinFET according to a comparative example; 
           [0029]      FIG. 5B  is a top view illustrating FinFET of the comparative example; and 
           [0030]      FIG. 5C  is a sectional view taken along a line A-A′ of  FIG. 5B . 
       
    
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS 
       [0031]    A background in which the inventor made the present invention will be described before embodiments of the invention are described. 
         [0032]    A configuration of FinFET  500  according to a comparative example will be described with reference to  FIGS. 5A to 5C .  FIG. 5A  is a perspective view illustrating FinFET  500  of the comparative example,  FIG. 5B  is a top view of FinFET  500 , and  FIG. 5C  is a sectional view taken along a line A-A′ of  FIG. 5B . 
         [0033]    Referring to  FIG. 5A , FinFET  500  includes a fin  508 , a gate electrode  503 , sidewalls  504 , a stress applying layer  505 , and a gate insulating film (not illustrated). FinFET  500  is insulated from an adjacent semiconductor element by an element isolation insulating film (SiO 2 )  502 . 
         [0034]    The fin  508  is formed on a semiconductor substrate main body  501  while formed integrally with the semiconductor substrate main body  501 . As illustrated in  FIG. 5B , the fin  508  includes source/drain regions  506  and a channel region  507  that is sandwiched between the source/drain regions  506 . 
         [0035]    The gate insulating film is formed on the fin  508  of the channel region  507 . 
         [0036]    As illustrated in  FIG. 5A , the gate electrode  503  is disposed so as to stride across the channel region  507 . The gate electrode  503  sandwiches the channel region  507  with the gate insulating film interposed therebetween. 
         [0037]    The sidewalls  504  are formed on both side surfaces of the gate electrode  503 . For example, the sidewall  504  is made of silicon nitride (Si 3 N 4 ). 
         [0038]    As illustrated in  FIGS. 5A to 5C , the stress applying layer  505  is formed such that, in the fin  508 , an upper surface of the source/drain region  506  and both side surfaces along a channel direction are covered therewith. The stress applying layer  505  is a semiconductor crystal layer that is formed on the source/drain region  506  by selective growth. A lattice constant of the semiconductor crystal layer is selected so as to be different from a lattice constant of a semiconductor crystal used for the source/drain region  506 . The different lattice constants apply a stress to the channel region  507  to generate a strain, which allows carrier mobility to be improved. 
         [0039]    For example, silicon germanium (SiGe) or silicon carbide (SiC) can be cited as a material for the stress applying layer  505  having the lattice constant different from that of silicon (Si) used for the fin  508 . In the case of SiGe, because SiGe has the lattice constant larger than that of Si, a compressive stress is applied to the channel region  507  in a gate-length direction (channel direction). Therefore, the hole mobility can be enhanced. On the other hand, in the case of SiC, because SiC has the lattice constant smaller than that of Si, a tensile stress is applied to the channel region  507  in the gate-length direction (channel direction). Therefore, the electron mobility can be enhanced. 
         [0040]    When the carrier mobility is enhanced, a driving current can be increased while a parasitic resistance of FinFET  500  is reduced. 
         [0041]    The stress applied to the channel region  507  increases with increasing volume of the stress applying layer  505 . 
         [0042]    Accordingly, the stress can be increased to some extent by thickening the stress applying layer  505 . However, because a size of FinFET is enlarged, there is a limitation from the viewpoint of integrating many FinFETs at high density. 
         [0043]    Generally, the element isolation insulating film  502  is made of a silicon oxide (SiO 2 ) film. In such cases, as illustrated in  FIGS. 5A to 5C , the inventor learned that a facet is generated when the stress applying layer  505  is selectively grown. 
         [0044]    That is, as illustrated in  FIGS. 5A and 5C , the facet is generated in a portion (portion F 1 ) in which the source/drain region  506  is in contact with a surface of the element isolation insulating film  502 . 
         [0045]    As illustrated in  FIG. 5B , the facet is also generated in a portion (portion F 2 ) in which the source/drain region  506  is in contact with the sidewall  504 . Although a mechanism by which the facet is generated is not completely explained at this moment, this is attributed to the following fact. That is, the crystal growth from a plane direction except for the facet is obstructed by the generation of the facet in the portion F 1 , and therefore the facet is generated in the portion F 2 . 
         [0046]    When the facets are generated, as can be seen from  FIGS. 5B and 5C , gaps are formed between the stress applying layer  505  and the element isolation insulating film  502  and between the stress applying layer  505  and the sidewall  504 . The volume of the stress applying layer  505  is smaller than that of the case in which the gaps are not generated. A gap is formed between the stress applying layer  505  and the sidewall  104  by the facet generated in the portion F 2 , and the stress applied to the channel region  507  is largely decreased, which causes a problem in that the stress applying layer  505  insufficiently applies the stress to the channel region  507  to insufficiently improve the parasitic resistance and the driving current. 
         [0047]    The inventor made the invention based on a unique technical knowledge. In the invention, the strain is sufficiently generated in the channel region by preventing the generation of the facet, whereby the driving current is increased while the parasitic resistance is reduced. 
         [0048]    Exemplary embodiments of the invention will be described below with reference to the drawings. A component having an equivalent function is designated by the same numeral, and the detailed description will not be repeated. 
       First Embodiment 
       [0049]    A first embodiment of the invention will be described below. The first embodiment differs from the comparative example in that a film  109  is provided. The element isolation insulating film  102  is covered with the film  109  made of silicon nitride (Si 3 N 4 ). 
         [0050]    A configuration of FinFET  100  of the first embodiment will be described with reference to  FIGS. 1A to 1C .  FIG. 1A  is a perspective view illustrating FinFET  100  of the first embodiment,  FIG. 1B  is a top view illustrating FinFET  100 , and  FIG. 1C  is a sectional view taken along a line A-A′ of  FIG. 1B . 
         [0051]    Referring to  FIG. 1A , FinFET  100  includes a fin  108 , a gate electrode  103 , sidewalls  104 , a stress applying layer  105 , and a gate insulating film (not illustrated). FinFET  100  is insulated from an adjacent semiconductor element by an element isolation insulating film (SiO 2 )  102 . 
         [0052]    The fin  108  is formed on a semiconductor substrate main body  101  while formed integrally with the semiconductor substrate main body  101 . As illustrated in  FIG. 1B , the fin  108  includes source/drain regions  106  and a channel region  107  that is sandwiched between the source/drain regions  106 . 
         [0053]    The gate insulating film is formed on the fin  108  of the channel region  107 . 
         [0054]    As illustrated in  FIG. 1A , the gate electrode  103  is disposed so as to stride across the channel region  107 . The gate electrode  103  sandwiches the channel region  107  with the gate insulating film interposed therebetween. 
         [0055]    The sidewalls  104  are formed on both side surfaces of the gate electrode  103 . For example, the sidewall  104  is made of silicon nitride (Si 3 N 4 ). 
         [0056]    As illustrated in  FIGS. 1A to 1C , the stress applying layer  105  is formed such that, in the fin  108 , an upper surface of the source/drain region  106  and both side surfaces along a channel direction are covered therewith. For example, silicon germanium (SiGe) or silicon carbide (SiC) is used as a material for the stress applying layer  105 . SiGe applies the compressive stress to the channel region  107  in the gate-length direction (channel direction) to enhance the hole mobility. Therefore, SiGe is suitable to a p-type FinFET. On the other hand, SiC applies the tensile stress to the channel region  107  in the gate-length direction (channel direction) to enhance the electron mobility. Therefore, SiC is suitable to an n-type FinFET. 
         [0057]    As illustrated in  FIGS. 1A to 1C , because the film  109  made of silicon nitride is formed on the element isolation insulating film  102 , the facets are not generated in the portion F 1  and the portion F 2 , and the stress applying layer  105  comes into contact with the film  109  and the sidewalls  104  with no gap, thereby preventing the decrease in volume of the stress applying layer  105 . Because the gap is not formed between the stress applying layer  105  and the sidewall  104 , the stress can efficiently be applied to the channel region  107 . Therefore, the higher stress is applied to the channel region  107  to increase the carrier mobility, so that the parasitic resistance can be decreased while the driving current is increased. 
         [0058]    A method for producing FinFET  100  according to the first embodiment will be described with reference to  FIGS. 2A to 2H . 
         [0059]    (1) Referring to  FIG. 2A , a first silicon oxide (SiO 2 ) film  111  and a first silicon nitride (Si 3 N 4 ) film  112  are sequentially deposited as a mask material on a semiconductor substrate (Si substrate)  101 A. Then, a photoresist is applied onto the first silicon nitride film  112  to form a photoresist film  113 . 
         [0060]    (2) Referring to  FIG. 2A , a photoresist film  113  is patterned by photolithography based on a shape of the fin  108 . 
         [0061]    (3) Referring to  FIG. 2B , the first silicon oxide film  111  and the first silicon nitride film  112  are processed by dry etching with the patterned photoresist film  113  as a mask. 
         [0062]    (4) Referring to  FIG. 2C , after the photoresist film  113  is removed, the semiconductor substrate  101 A is etched to form the fin  108  with the first silicon nitride film  112  as the mask. The fin  108  is formed on the semiconductor substrate main body  101  while formed integrally with the semiconductor substrate main body  101 . For example, the fin  108  has a height of 100 nm to 200 nm. 
         [0063]    (5) Referring to  FIG. 2D , a second silicon oxide film  102 A is deposited on the semiconductor substrate main body  101 , the fin  108 , and the first silicon nitride film  112 . 
         [0064]    (6) Referring to  FIG. 2D , the second silicon oxide film  102 A is planarized by chemical mechanical polishing (CMP) with the first silicon nitride film  112  as a stopper. 
         [0065]    (7) Referring to  FIG. 2E , the second silicon oxide film  102 A is retreated to form the element isolation insulating film  102  by the dry etching with the first silicon nitride film  112  as the mask. Preferably, the element isolation insulating film  102  is formed thinner by at least a thickness of the film  109  such that the volume of the stress applying layer  105  is not decreased by the film  109  formed in the subsequent process. For example, the element isolation insulating film  102  has the thickness of 20 nm to 30 nm. 
         [0066]    (8) Referring to  FIG. 2F , a second silicon nitride film  109 A is deposited on the element isolation insulating film  102 , the fin  108 , and the first silicon nitride film  112 . 
         [0067]    (9) Referring to  FIG. 2F , the second silicon nitride film  109 A is planarized by CMP with the first silicon oxide film  111  as the stopper. 
         [0068]    (10) Referring to  FIG. 2G , the first silicon oxide film  111  is masked, the second silicon nitride film  109 A is retreated by the dry etching to form the film  109  with which the element isolation insulating film  102  is covered. For example, the film  109  has the thickness of 10 nm. The sum of the thicknesses of the element isolation insulating film  102  and film  109  is substantially equal to the thickness of the element isolation insulating film  502  of the comparative example. 
         [0069]    (11) After the first silicon oxide film  111  is removed, the gate insulating film (not illustrated) is deposited on the fin  108 . Then, referring to  FIG. 2H , polysilicon  103 A is deposited on the gate insulating film and the film  109 . Therefore, the fin  108  is buried in the polysilicon  103 A. 
         [0070]    (12) As illustrated in  FIG. 2H , a third silicon nitride film  114  is deposited as a mask material on the polysilicon  103 A. 
         [0071]    (13) As illustrated in  FIG. 2H , the photoresist is applied onto the third silicon nitride film  114  to form a photoresist film  115 . Then, the photoresist film  115  is patterned by photolithography based on a shape of the gate electrode. 
         [0072]    (14) The third silicon nitride film  114  is processed by the dry etching with the patterned photoresist film  115  as the mask. 
         [0073]    (15) Then, after photoresist film  115  is removed, the polysilicon  103 A is processed by the dry etching with the third silicon nitride film  114  as the mask, thereby forming the gate electrode  103 . As illustrated in  FIGS. 1A and 1B , the gate electrode  103  is formed so as to stride across the channel region  107  of the fin  108 . The gate insulating film acts as an etching stopper in etching the polysilicon  103 A. 
         [0074]    (16) The gate insulating film deposited on the source/drain region  106  is removed by the etching. 
         [0075]    (17) Then, ion injection is performed to the source/drain region  106 , thereby forming an extension region (not illustrated). 
         [0076]    (18) Then, a fourth silicon nitride film  104 A (not illustrated) is deposited on the gate electrode  103 , the source/drain region  106 , and the film  109 . Then, overall etching is performed to the fourth silicon nitride film  104 A to form the sidewalls  104  (sidewall spacers) on both the side surfaces of the gate electrode  103 . The sidewalls  104  are used to form a Lightly Doped Drain (LDD) structure. The fourth silicon nitride film  104 A with which the fin  108  is removed in the etching back. 
         [0077]    (19) The ion injection is performed to the source/drain region  106 , thereby forming the LDD structure. 
         [0078]    (20) The stress applying layer  105  is formed on the source/drain region  106  by the selective growth. 
         [0079]    As illustrated in  FIG. 1C , because the facet is not generated in the portion F 1 , the stress applying layer  105  is in contact with the film  109  with no gap. As illustrated in  FIG. 1B , because the facet is not generated in the portion F 2 , the stress applying layer  105  is in contact with the sidewall  104  with no gap. Therefore, the volume of the stress applying layer  105  becomes larger than that of the stress applying layer  505  of the comparative example, so that the larger stress can be applied to the channel region  107  sandwiched between the source/drain regions  106 . 
         [0080]    (21) The third silicon nitride film  114  on the gate electrode  103  is removed. It is not always necessary to remove the third silicon nitride film  114 . 
         [0081]    FinFET  100  of  FIG. 1A  is formed through the above-described processes. The following processes are similar to those of the conventional FinFET. That is, a silicide film is formed in the surfaces of the gate electrode  103  and stress applying layer  105  (source/drain region  106 ). Then, an inter-layer insulating film is deposited so as to bury FinFET  100 . Then, a contact plug is formed in the inter-layer insulating film, and a metal interconnection is formed on the inter-layer insulating film. The metal interconnection is electrically connected to FinFET  100  through the contact plug. 
         [0082]    In the first embodiment, the silicon nitride is cited as the material used for the film  109  with which the element isolation insulating film  102  is coated. However, the material used for the film  109  is not limited to the silicon nitride. For example, silicon carbide nitride (SiCN) may be used as the material for the film  109 . Instead of the silicon nitride, the silicon oxide may be used as the material for the sidewall  104 . 
         [0083]    As described above, in the first embodiment, because the film  109  is formed on the element isolation insulating film  102 , the stress applying layer  105  is in contact with the film  109  with no gap, and the stress applying layer  105  is also in contact with the sidewall  104  with no gap. 
         [0084]    Therefore, the stress applying layer  105  can apply the larger stress to the channel region  107  to enhance the carrier mobility. As a result, because the channel resistance is decreased, the parasitic resistance of FinFET can be decreased. The higher driving current can also be obtained. 
       Second Embodiment 
       [0085]    A second embodiment of the invention will be described below. The second embodiment differs from the first embodiment in that a silicon on insulator (SOI) substrate is used. 
         [0086]    A configuration of FinFET  200  of the second embodiment will be described with reference to  FIGS. 3A to 3C .  FIG. 3A  is a perspective view illustrating FinFET  200  of the second embodiment,  FIG. 3B  is a top view illustrating FinFET  200 , and  FIG. 3C  is a sectional view taken along a line A-A′ of  FIG. 3B . 
         [0087]    Referring to  FIG. 3A , FinFET  200  includes a fin  208 , a gate electrode  203 , sidewalls  204 , a stress applying layer  205 , and a gate insulating film (not illustrated). FinFET  200  is insulated from an adjacent semiconductor element by a BOX (Buried Oxide) layer  202  that is of a buried silicon oxide film. 
         [0088]    The fin  208  is formed on the BOX layer  202 . As illustrated in  FIG. 3B , the fin  208  includes source/drain regions  206  and a channel region  207  that is sandwiched between the source/drain regions  206 . 
         [0089]    The gate insulating film is formed on the fin  208  of the channel region  207 . 
         [0090]    As illustrated in  FIG. 3A , the gate electrode  203  is disposed so as to stride across the channel region  207 . The gate electrode  203  sandwiches the channel region  207  with the gate insulating film interposed therebetween. 
         [0091]    The sidewalls  204  are formed on both side surfaces of the gate electrode  203 . For example, the sidewall  204  is made of silicon nitride (Si 3 N 4 ). 
         [0092]    As illustrated in  FIGS. 3A to 3C , the stress applying layer  205  is formed such that, in the fin  208 , an upper surface of the source/drain region  206  and both side surfaces along the channel direction are covered therewith. For example, silicon germanium (SiGe) or silicon carbide (SiC) is used as a material for the stress applying layer  205 . SiGe applies the compressive stress to the channel region  207  in the gate-length direction (channel direction) to enhance the hole mobility. Therefore, SiGe is suitable to the p-type FinFET. On the other hand, SiC applies the tensile stress to the channel region  207  in the gate-length direction (channel direction) to enhance the electron mobility. Therefore, SiC is suitable to the n-type FinFET. 
         [0093]    As illustrated in  FIGS. 3A to 3C , because a film  209  made of silicon nitride is formed on the BOX layer  202 , the facets are not generated in the portion F 1  and the portion F 2 , and the stress applying layer  205  comes into contact with the film  209  and the sidewalls  204  with no gap, thereby preventing the decrease in volume of the stress applying layer  205 . Because the gap is not formed between the stress applying layer  205  and the sidewall  204 , the stress can efficiently be applied to the channel region  207 . Therefore, the higher stress is applied to the channel region  207  to increase the carrier mobility, so that the parasitic resistance can be decreased while the driving current is increased. 
         [0094]    A method for producing FinFET  200  of the second embodiment will be described with reference to  FIGS. 4A to 4E . 
         [0095]    (1) Referring to  FIG. 4A , a first silicon oxide (SiO 2 ) film  211  and a first silicon nitride (Si 3 N 4 ) film  212  are sequentially deposited as a mask material on a SOI substrate  220 . In the SOI substrate  220 , the BOX layer  202  made of silicon oxide and a SOI (Silicon On Insulator) layer  208 A made of single-crystal silicon are sequentially laminated on the support substrate (Si substrate)  201 . Then, the photoresist is applied onto the first silicon nitride film  212  to form a photoresist film  213 . 
         [0096]    (2) As illustrated in  FIG. 4A , the photoresist film  213  is patterned by the photolithography based on a shape of the fin  208 . 
         [0097]    (3) Referring to  FIG. 4B , the first silicon oxide film  211  and the first silicon nitride film  212  are processed by the dry etching with the patterned photoresist film  213  as the mask. 
         [0098]    (4) Referring to  FIG. 4C , after the photoresist film  213  is removed, the SOI layer  208 A is etched with the first silicon nitride film  212  as the mask until the BOX layer  202  is exposed, thereby forming the fin  208 . For example, the fin  208  has a height of 100 nm to 200 nm. 
         [0099]    (5) Referring to  FIG. 4D , a second silicon nitride film  209 A is deposited on the BOX layer  202 , the fin  208 , and the first silicon nitride film  212 . 
         [0100]    (6) As illustrated  FIG. 4D , the second silicon nitride film  209 A is planarized by CMP with the first silicon oxide film  211  as the stopper. 
         [0101]    (7) Referring to  FIG. 4E , the second silicon nitride film  209 A is retreated to form the film  209  by the dry etching with the first silicon oxide film  211  as the mask. The BOX layer  202  is covered with the film  209 . For example, the film  209  has the thickness of 10 nm. 
         [0102]    Because the following processes are similar to those of the first embodiment, the description will not be repeated. 
         [0103]    In the second embodiment, the silicon nitride is cited as the material used for the film  209  with which the BOX layer  202  is coated. However, the material used for the film  209  is not limited to the silicon nitride. For example, silicon carbide nitride (SiCN) may be used as the material for the film  209 . Instead of the silicon nitride, the silicon oxide may be used as the material for the sidewall  204 . 
         [0104]    As described above, in the second embodiment, because the film  209  is formed on the BOX layer  202 , the stress applying layer  205  is in contact with the film  209  with no gap, and the stress applying layer  205  is also in contact with the sidewall  204  with no gap. 
         [0105]    Therefore, the stress applying layer  205  can apply the larger stress to the channel region  207  to enhance the carrier mobility. As a result, because the channel resistance is decreased, the parasitic resistance of FinFET can be decreased. The higher driving current can also be obtained. 
         [0106]    Additional advantages and modifications will readily occur to those skilled in the art. 
         [0107]    Therefore, the invention in its broader aspects is not limited to the specific details and representative embodiments shown and described herein. 
         [0108]    Accordingly, various modifications may be made without departing from the spirit or scope of the general inventive concepts as defined by the appended claims and their equivalents.