Abstract:
A semiconductor device includes a substrate that has a surface. The semiconductor further includes a fin disposed on the surface and including a semiconductor member. The semiconductor further includes a spacer disposed on the surface, having a type of stress, and overlapping the semiconductor member in a direction parallel to the surface. A thickness of the spacer in a direction perpendicular to the surface is less than a height of the semiconductor member in the direction perpendicular to the surface.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims priority to and benefit of Chinese Patent Application No. 201210351667.7, filed on Sep. 20, 2012 and entitled “Semiconductor Device and Manufacturing Method thereof”, which is incorporated herein by reference in its entirety. 
     BACKGROUND 
     1. Field of the Invention 
     The present invention relates to semiconductor device and manufacturing method thereof. 
     2. Description of the Related Art 
     For satisfying critical dimension (CD) requirements, fin semiconductor devices have been implemented. As an example, a fin field effect transistor (FinFET) may include a channel formed at a fin structure. On the other hand, for improving performance of semiconductor devices, stress devices that involve stress effects have been implemented. 
     SUMMARY 
     One or more embodiments of the invention may be related to a semiconductor device that includes a substrate having a surface. The semiconductor device may further include a first fin disposed on the surface and including a first semiconductor member. The semiconductor device may further include a first spacer disposed on the surface, having a first type of stress, and overlapping the first semiconductor member in a direction parallel to the surface. A thickness of the first spacer in a direction perpendicular to the surface may be less than a height of the first semiconductor member in the direction perpendicular to the surface. 
     In one or more embodiments, the semiconductor device may include a second fin disposed on the surface and including a second semiconductor member. The semiconductor device may further include a second spacer disposed on the surface, having a second type of stress that is different from the first type of stress, and overlapping the second semiconductor member in the direction parallel to the surface. A thickness of the second spacer in the direction perpendicular to the surface may be less than a height of the second semiconductor member in the direction perpendicular to the surface. 
     In one or more embodiments, the first fin may be associated with an N-type device part, and the second fin may be associated with a P-type device part. The first-type stress material may be a compressive stress material, and the second-type stress material may be a tensile stress material. 
     In one or more embodiments, the semiconductor device may include a gate enwrapping at least a portion of the first semiconductor member, at least a portion of the first spacer, least a portion of the second semiconductor member, and at least a portion of the second spacer. 
     In one or more embodiments, the first fin further includes a mask, and at least a portion of the mask is enwrapped by the gate and is disposed between the first semiconductor and a portion of the gate. 
     In one or more embodiments, the semiconductor device may include an insulating layer disposed on the surface and covering at least a portion of the first spacer. The semiconductor device may further include a third spacer overlapping the insulating layer in the direction perpendicular to the surface, overlapping the first spacer in the direction perpendicular to the surface, overlapping the first fin in the direction parallel to the surface, and having the second type of stress. 
     In one or more embodiments, the semiconductor device may include a fourth spacer overlapping the insulating layer in the direction perpendicular to the surface, overlapping the second spacer in the direction perpendicular to the surface, overlapping the second fin in the direction parallel to the surface, and having the first type of stress. 
     In one or more embodiments, the semiconductor device may include at least one of a first intermediate layer and a second intermediate layer. The first intermediate layer may be disposed between the third spacer and the first spacer and directly contacting at least one of the third spacer and the first spacer. The second intermediate layer may be disposed between the third spacer and the insulating layer and directly contacting at least one of the third spacer and the insulating layer. 
     In one or more embodiments, the semiconductor device may include an intermediate layer disposed between the first spacer and the first semiconductor member and directly contacting at least one of the first spacer and the first semiconductor member. 
     In one or more embodiments, the semiconductor device may include an insulating layer disposed on the surface and covering at least a portion of the first spacer. The semiconductor device may further include a second spacer overlapping the insulating layer in the direction perpendicular to the surface, overlapping the first spacer in the direction perpendicular to the surface, overlapping the first fin in the direction parallel to the surface, and having a second type of stress that is different from the first type of stress. 
     In one or more embodiments, the semiconductor device may include an insulating layer disposed on the surface and covering at least a portion of the first spacer. The semiconductor device may further include a gate enwrapping at least a portion of the first semiconductor member and overlapping at least a portion of the insulating layer in the direction perpendicular to the surface. 
     One or more embodiments of the invention may be related to a method for manufacturing a semiconductor device. The method may include providing a substrate that has a surface. The method may further include providing a first fin on the surface, the first fin including a first semiconductor member. The method may further include forming a first spacer on the surface, the first spacer having a first type of stress and overlapping the first semiconductor member in a direction parallel to the surface. A thickness of the first spacer in a direction perpendicular to the surface may be less than a height of the first semiconductor member in the direction perpendicular to the surface. 
     In one or more embodiments, the method may include providing a second fin on the surface, the second fin including a second semiconductor member. The method may further include forming a second spacer on the surface, the second spacer having a second type of stress that is different from the first type of stress and overlapping the second semiconductor member in the direction parallel to the surface. A thickness of the second spacer in the direction perpendicular to the surface may be less than a height of the second semiconductor member in the direction perpendicular to the surface. 
     In one or more embodiments, the method may include forming an insulating layer on the surface, the insulating layer covering at least a portion of the first spacer. The method may further include forming a third spacer, wherein the third spacer overlaps the insulating layer in the direction perpendicular to the surface, overlaps the first spacer in the direction perpendicular to the surface, overlaps the first fin in the direction parallel to the surface, and has the second type of stress. 
     In one or more embodiments, the method may further include forming a fourth spacer, wherein the fourth spacer overlaps the insulating layer in the direction perpendicular to the surface, overlaps the second spacer in the direction perpendicular to the surface, overlaps the second fin in the direction parallel to the surface, and has the first type of stress. 
     One or more embodiments of the invention may be related to a method for manufacturing a semiconductor device. The method may include providing a first fin and a second fin on a substrate. The method may further include disposing a first-type stress material on the substrate such that the first-type stress material convers the first fin and the second fin, a first portion of the first-type stress material corresponding to the first fin, a second portion of the first-type stress material corresponding to the second fin. The method may further include disposing a first resist pattern over the first-type stress material such that the first resist pattern covers the first portion of the first-type stress material without covering the second portion of the first-type stress material. The method may further include using the first resist pattern as a mask to remove the second portion of the first-type stress material. The method may further include removing the first resist pattern. The method may further include disposing a second-type stress material over the first portion of the first-type stress material and over the second fin, the second-type stress material being different from the first-type stress material, a first portion of the second-type stress material corresponding to the first fin, a second portion of the second-type stress material corresponding to the second fin. The method may further include disposing a second resist pattern over the second-type stress material such that the first resist pattern covers the second portion of the second-type stress material without covering the first portion of the first-type stress material. The method may further include using the second resist pattern as a mask to remove the first portion of the second-type stress material. The method may further include etching the first portion of the first-type stress material to form a first spacer at a first corner, the first corner being formed by the substrate and the first fin. The method may further include etching the second portion of the second-type stress material to form a second spacer at a second corner, the second corner being formed by the substrate and the second fin. 
     In one or more embodiments, the method may include, before the disposing the first resist pattern, disposing an intermediate layer on the first-type stress material, a first portion of the intermediate layer being corresponding to the first fin, a second portion of the intermediate layer corresponding to the second fin, wherein the resist pattern covers the first portion of the intermediate layer and exposes the second portion of the intermediate layer. The method may further include using the first resist pattern as a mask to remove the second portion of the intermediate layer. 
     In one or more embodiments, the method may further include disposing the first portion of the second-type stress material on the first portion of the intermediate layer. The method may further include using the second resist pattern as a mask to remove the first portion of the intermediate layer. 
     In one or more embodiments, the method may include forming a gate that enwraps at least a portion of the first fin, at least a portion of the first spacer, least a portion of the second fin, and at least a portion of the second spacer. 
     In one or more embodiments, the method may include disposing an insulating layer on the substrate such that the insulating layer covers at least a portion of the first spacer and at least a portion of the second spacer. The method may further include forming a gate that enwraps at least a portion of the first fin, enwraps at least a portion of the second fin, and overlaps at least a portion of the insulating layer. 
     In one or more embodiments, the method may include using the first fin to form an N-type device part. The method may further include using the second fin to form a P-type device part. The first-type stress material may be a compressive stress material, and the second-type stress material may be a tensile stress material. 
     One or more embodiments of the invention may be related to a semiconductor device that includes the following elements: a substrate with at least one fin formed on a surface thereof, the fin having a semiconductor layer; and a first spacer formed on a lower part of a sidewall of the at least one fin, a thickness of the first spacer being less than a height of the semiconductor layer in the at least one fin; wherein, the first spacer is formed of a first stress material of a first type of stress. 
     In one or more embodiments, the semiconductor device may further include the following elements: an insulating layer formed over the surface, the insulating layer covering at least a portion of the first spacer; and a second spacer formed on at least a portion of the sidewall of the at least one fin, over the insulating layer, and over the first spacer uncovered by the insulating layer if the first spacer uncovered by the insulating layer exists; wherein, the second spacer is formed of a second stress material having a second type of stress, the second type of stress is reverse, in nature, to the first type of stress. 
     In one or more embodiments, the at least one fin includes a first fin for forming a P-type device and a second fin for forming an N-type device, and wherein the first spacer for the first fin is formed of a tensile stress material, and the first spacer for the second fin is formed of a compressive stress material. 
     In one or more embodiments, the at least one fin includes a first fin for forming a P-type device and a second fin for forming an N-type device, and wherein the first spacer for the first fin is formed of a tensile stress material and the second spacer for the first fin is formed of a compressive stress material; the first spacer for the second fin is formed of a compressive stress material and the second spacer for the second fin is formed of a tensile stress material. 
     In one or more embodiments, the semiconductor device may include a gate formed over the surface, the gate enwrapping at least a portion of the semiconductor layer of the at least one fin. 
     In one or more embodiments, the semiconductor device may include a gate formed over the insulating layer and over the first spacer uncovered by the insulating layer if the first spacer uncovered by the insulating layer exists, the gate enwrapping at least a portion of the semiconductor layer of the at least one fin. 
     In one or more embodiments, the at least one fin may include a hard mask layer over the semiconductor layer. 
     In one or more embodiments, the substrate may include a semiconductor layer directly below the at least one fin. 
     In one or more embodiments, the semiconductor device may include an intermediate layer between the first spacer and the fin and/or between the first spacer and the surface of the substrate. 
     In one or more embodiments, the semiconductor device may include an intermediate layer between the second spacer and the fin. 
     One or more embodiments of the invention may be related to a method for manufacturing a semiconductor device. The method may include the following steps: providing a substrate with at least one fin formed on a surface thereof, the fin including a semiconductor layer; and forming a first spacer on a lower part of a sidewall of the at least one fin, the first spacer having a thickness less than a height of the semiconductor layer in the at least one fin; wherein, the first spacer is formed of a first stress material of a first type of stress. 
     In one or more embodiments, the method may include forming an insulating layer over the surface, the insulating layer covering at least a portion of the first spacer; and forming a second spacer on at least a portion of a sidewall of the at least one fin, over the insulating layer and the first spacer uncovered by the insulating layer if the first spacer uncovered by the insulating layer exists. The second spacer is formed of a second stress material of a second type of stress, and the second type of stress is reverse, in nature, to the first type of stress. 
     In one or more embodiments, the at least one fin includes a first fin for forming a P-type device and a second fin for forming an N-type device, the first spacer for the first fin is formed of a tensile stress material, and the first spacer for the second fin is formed of a compressive stress material. 
     In one or more embodiments, the at least one fin includes a first fin for forming a P-type device and a second fin for forming an N-type device. The first spacer for the first fin is formed of a tensile stress material, and the second spacer for the first fin is formed of a compressive stress material. The first spacer for the second fin is formed of a compressive stress material, and the second spacer for the second fin is formed of a tensile stress material. 
     In one or more embodiments, the method may include forming a gate over the surface, the gate enwrapping at least a portion of the semiconductor layer of the at least one fin. 
     In one or more embodiments, the method may include forming a gate over the insulating layer, the gate enwrapping at least a portion of the semiconductor layer of the at least one fin. 
     In one or more embodiments, the at least one fin may include a hard mask layer over the semiconductor layer. 
     In one or more embodiments, the substrate may include a semiconductor layer directly below the at least one fin. 
     In one or more embodiments, the method may include forming an intermediate layer on the sidewall of the at least one fin and/or on the surface of the substrate, prior to forming the first spacer, such that in the case where the first spacer is subsequently formed, the intermediate layer is between the first spacer and the fin and/or between the first spacer and the surface of the substrate. 
     In one or more embodiments, the method may include forming an intermediate layer on the sidewall of the at least one fin, prior to forming the second spacer, such that in the case where the second spacer is subsequently formed, the intermediate layer is between the second spacer and the fin. 
     According to embodiments of the present invention, carrier mobility in respective desired portions (e.g. a portion below a channel formation region between a source and a drain) of the n-type device and/or p-type device can be minimized using stress effect, and thus leakage between the source and the drain can be minimized. Additionally or alternatively, carrier mobility of the channel formation region can be enhanced, and thus device performance can be optimized. 
     Other features and advantages of the present invention will become apparent from the following detailed description in conjunction with the drawings. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
       The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate embodiments of the invention and, together with the description, serve to explain the principles of the invention. By reading the following detailed description with reference to the accompanying drawings, the present invention can be better understood. In the drawings: 
         FIG. 1  illustrates a cross-sectional view of a semiconductor substrate and a fin formed on a surface of the semiconductor substrate according to one or more embodiments of the present invention. 
         FIG. 2  illustrates a cross-sectional view of a semiconductor device according to one or more embodiments of the present invention, wherein a first spacer is formed on a lower part of a sidewall of the fin on the semiconductor substrate of  FIG. 1 . 
         FIG. 3  illustrates a cross-sectional view of a semiconductor device according to one or more embodiments of the present invention, wherein, after formation of the first spacer, an insulating layer covering at least a portion of the first spacer is formed on the surface of the semiconductor substrate. 
         FIG. 4  illustrates a cross-sectional view of a semiconductor device according to one or more embodiments of the present invention, wherein a second spacer is formed over the insulating layer and the first spacer (if the first spacer exists). 
         FIG. 5 ,  FIG. 6 ,  FIG. 7 ,  FIG. 8 ,  FIG. 9 , and  FIG. 10  schematically illustrate a process for forming the first spacer according to one or more embodiments of the present invention. 
         FIG. 11  illustrates a perspective view of a semiconductor device in which a gate is formed after the formation of the first spacer according to one or more embodiments of the present invention. 
         FIG. 12  illustrates a perspective view of a semiconductor device in which a gate is formed after the formation of the insulating layer according to one or more embodiments of the present invention. 
         FIG. 13  illustrates a cross-sectional view of a semiconductor device for explaining a step of forming a second spacer according to one or more embodiments of the present invention. 
     
    
    
     It should be understood that, these drawings are illustrative and are not intended to limit the scope of the present invention. In the drawings, components may not have been drawn strictly to scale or shown according to their actual shapes. Some components (e.g. layers or parts) may be enlarged relative to others, so as to more clearly illustrate the principles of the present invention. Details that may obscure the gist of the present invention may not be shown in the drawings. 
     DESCRIPTION OF EMBODIMENTS 
     Hereinafter, embodiments of the present invention will be described in conjunction with the accompanying drawings. 
     As used herein, the term “semiconductor device” may be referred to a device that can operate partially or fully using semiconductor attributes. 
     Although the terms first, second, etc. may be used herein to describe various signals, elements, components, regions, layers, and/or sections, these signals, elements, components, regions, layers, and/or sections should not be limited by these terms. These terms may be used to distinguish one signal, element, component, region, layer, or section from another signal, region, layer or section. Thus, a first signal, element, component, region, layer, or section discussed below may be termed a second signal, element, component, region, layer, or section without departing from the teachings of the present invention. The description of an element as a “first” element may not require or imply the presence of a second element or other elements. The terms first, second, etc. may also be used herein to differentiate different categories of elements. For conciseness, the terms first, second, etc. may represent first-type (or first-category), second-type (or second-category), etc., respectively. 
       FIG. 1  illustrates a cross-sectional view of a semiconductor substrate  101  and at least one fin, for example, a fin  107  and a fin  109 , formed on one or more surfaces of the semiconductor substrate  101  according to one or more embodiments of the present invention. Fins  107  and  109  can include semiconductor layers  1071  and  1091 , respectively. Fins  107  and  109  can further include hard mask layers  1070  and  1090  disposed on the semiconductor layers  1071  and  1091 , respectively. One of ordinary skill in the art can select materials for the semiconductor layers and the hard mask layers as appropriate. In one or more embodiments, there can be more or fewer fins. In one or more embodiments, the two fins can have one or more positional relations different from the relation illustrated in  FIG. 1 . 
     In one or more embodiments, the substrate  101  can be a bulk substrate, such as a bulk silicon substrate. In one or more embodiments, the substrate  101  can comprise a semiconductor layer directly below the at least one fin. The present invention is not limited to this configuration. 
     At least one of the fins can be used for forming an N-type device or a P-type device (such as an NMOS FinFET or a PMOS FinFET). In one or more embodiments, as illustrated in the figures, the fin  107  may be used for forming an N-type device, and the fin  109  may be used for forming a P-type device. The left part of the device illustrated in each figure of the figures can be referred to as an N-type device part (or N-type part for conciseness); the right part of the device illustrated in each figure of the figures can be referred to as a P-type device part (or P-type part for conciseness). It should be understood that the present invention is not limited to this arrangement. 
       FIG. 2  illustrates a cross-sectional view of first-layer spacers  201  and  203  (or first spacers  201  and  203  for conciseness) disposed on sidewalls of fins  107  and  109  on the semiconductor substrate  101  of  FIG. 1  according to one or more embodiments of the present invention. As shown in  FIG. 2 , the first spacer(s)  201  can be formed on a lower part of a sidewall of fin  107  (at a corner formed by the fin  107  and the substrate  101 ), and the first spacer (s)  203  can be formed on a lower part of a sidewall of fin  109  (at a junction of the fin  109  and the substrate  101 ). 
     A first spacer for a particular fin can be formed of a first stress material having a particular first type of stress. For example, for fin  107 , which is configured for forming an N-type device, the first spacer  201  may be formed of a compressive stress material (such as compressive stress silicon nitride). For fin  109 , which is configured for forming a P-type device, the first spacer  203  may be formed of a tensile stress material (such as tensile stress silicon nitride). 
     The thickness (T 1 ) of each of the first spacers  201  and  203  is less than the height (Hsemi) of the semiconductor layer in respective fins. In one or more embodiments, thickness T 1  of at least one of the first spacers  201  and  203  may be ¾ or less than ¾ of the height of the semiconductor layer in associated fin(s). 
     The top of first spacer, which may be buried under the STI dielectric, should be close to the bottom of the channel area. In one or more embodiments, the fin above STI dielectric is more than ¼ of the height of the semiconductor layer in associated fin(s). In one or more embodiments, the first spacer can have a thickness in a range of about 50 nm to 500 nm, which may be decided based on the height of the fin(s). 
     In one or more embodiments, a first spacer may directly contact the associated fin and may directly contact the underlying substrate, as illustrated in  FIG. 2 . In one or more embodiments, an intermediate layer can be formed between a first spacers (e.g., at least one of the first spacers  201  and  203 ) and the associated fin; for example, an intermediate layer may be disposed between the first spacer and the semiconductor layers in the associated fin. In one or more embodiments, an intermediate layer may be disposed between a first spacer and the substrate. One or more of the spacer-fin intermediate layer and the spacer-substrate intermediate layer may include a native oxide layer and/or one or more other functional layers. The intermediate layer(s) may not adversely affect the stress effect exerted by the spacer on the associated fin and/or the substrate. 
       FIGS. 5 to 10  illustrate cross-sectional views schematically showing a process for forming the first spacers according to one or more embodiments of the present invention. 
     As illustrated in  FIG. 5 , a layer of compressive stress material  501  is formed on the substrate  101 , on which fins  107  and  109  are formed. Thereafter, an intermediate layer  503  (e.g. silicon oxide layer) is formed on the layer of compressive stress material  501 . In one or more embodiments, the compressive stress material  501  can be formed of compressive stress silicon nitride and can be formed using a chemical vapor deposition (CVD) process under the following process conditions: a temperature in a range of about 400° C. to 500° C., a pressure in a range of about 1 torr to 10 torr, a high-frequency power in a range of about 50 w to 200 w and a low-frequency power in a range of about 10 w to 100 w, an SiH 4  flow rate in a range of about 20 sccm to 200 sccm, an NH 3  flow rate in a range of about 200 sccm to 1500 sccm, an H 2  flow rate in a range of about 1000 sccm to 5000 sccm, and Ar gas flow rate in a range of about 1000 sccm to 5000 sccm. In some embodiments, the compressive stress material may have a compressive stress in a range of about −4.0 GPa to −1.0 GPa, wherein the range may be determined according to process limitations, wherein a high compressive stress may be preferred, and wherein the notation represents compressive stress. The high-frequency power and the low-frequency power may be applied during the process of film deposition by different generators. The low-frequency power can increase compressive stress by bombardment. 
     Next, as illustrated in  FIG. 6 , a resist pattern  601  is formed on the intermediate layer  503  so as to cover the N-type device part while exposing the P-type device part. Next, the intermediate layer  503  and the layer of compressive stress material  501  in the P-type device part are removed with the resist pattern  601  being used as a mask, as illustrated in  FIG. 7 . 
     Thereafter, as illustrated in  FIG. 8 , after removing of the resist pattern  601 , a layer of tensile stress material  801  is deposited on the substrate  101 . As illustrated in  FIG. 8 , the layer of tensile stress material  801  is formed on both the N-type device part and the P-type device part. In one or more embodiments, the tensile stress material  801  can be formed of tensile stress silicon nitride and can be formed using a CVD process under the following process conditions: a temperature in a range of about 300° C. to 500° C., a pressure in a range of about 1 torr to 10 torr, a high-frequency power in a range of about 50 w to 300 w, an SiH 4  flow rate in a range of about 20 sccm to 200 sccm, an NH 3  flow rate in a range of about 200 sccm to 1500 sccm, and an N 2  flow rate in a range of about 500 sccm to 5000 sccm. In some embodiments, the tensile stress material can have a tensile stress in a range of about 0.8 GPa to 2.0 GPa, wherein the range may be determined based on process limitations, and wherein a high tensile stress may be preferred. 
     Subsequently, as illustrated in  FIG. 9 , a resist pattern  901  is formed so as to cover the P-type part. Thereafter, the layer of tensile stress material  801  and the intermediate layer  503  in the N-type part are removed with the resist pattern  901  being used as a mask, as illustrated in  FIG. 10 . 
     Thereafter, the thus formed stress material layers  801  and  501  are etched, thereby forming the first spacers  201  and  203 , as illustrated in  FIG. 2 . 
       FIG. 11  illustrates a perspective view of a semiconductor device in which a gate is formed after the formation of the first spacers according to one or more embodiments of the present invention. After the structure as illustrated in  FIG. 2  has been formed, a gate  1101  can be formed on the surface  110  of the substrate on which the fins are formed, and the gate  1101  enwraps at least a portion of the fins, as illustrated in  FIG. 11 . The gate  1101  can be formed with use of the technologies known in the art, and thus details thereof are omitted. In one or more embodiments, as illustrated in  FIG. 11 , the gate  1101  may have a hard mask  1103  thereon. In one or more embodiments, that the semiconductor device may not include the hard mask  1103  or a hard mask disposed on the gate  1101 . As would be appreciated by one of ordinary skill in the art, a source and a drain can be formed in the fins in a self-aligned manner after the formation of the gate  1101 . 
     According to one or more embodiments of the present invention, carrier mobility in desired portions (e.g., the portion below the channel formation region between the source and the drain) of the N-type device and/or P-type device can be minimized by stress effects associated with the spacers. Advantageously, leakage between the source and the drain can be minimized. 
       FIG. 3  illustrates a cross-sectional view of a semiconductor device according to one or more embodiments of the present invention, wherein, after formation of the first spacers  201  and  203  illustrated in  FIG. 2 , an (electrically) insulating layer  301  is formed on the surface  110  of the semiconductor substrate  101  so as to cover at least a portion of the first spacers  201  and  203 . In one or more embodiments, after the first spaces  201  and  203  have been formed, insulating material, such as silicon oxide, can be deposited over the surface  110  of the substrate  101  (on which the fin is formed); subsequently, the deposited insulating layer can be etched back so as to form the insulating layer  301 . Etching back of this insulating layer can be controlled such that the upper surface of the insulating layer  301  is substantially flush with or higher than the top of the first spacers  201  and  203 , for facilitating subsequent processes. In one or more embodiments, the upper surface of the insulating layer  301  may be lower than the top of the first spacers  201  and  203 . The insulating layer  301  can substantially cover at least portions of the first spacers  201  and  203 . 
     Thereafter, as illustrated in  FIG. 4 , second-layer spacers  401  and  403  (or second spacers  401  and  403  for conciseness) are formed on at least portions of the sidewalls of the fins. These second spacers are formed over the insulating layer  301  (and may also be formed over portions of the first spacers not covered by the insulating layer). In one or more embodiments, the second spacers may be formed of one or more stress materials. For a particular fin, the associated second spacer can be formed of a second stress material of a second type of stress that is reverse, in nature, to the first type of stress of the first spacer associated with this fin. 
     For example, in the N-type device part, that is, for the fin  107  for forming the N-type device, the second spacer  401  may be formed of a tensile stress material, while the first spacer  201  may be formed of a compressive stress material. As another example, in the P-type device part, that is, for the fin  109  for forming the P-type device, the second spacer  403  may be formed of a compressive stress material, while the first spacer  203  may be formed of a tensile stress material. Analogous to the first stress materials, the second stress materials can be compressive stress silicon nitride and/or tensile stress silicon nitride. 
     A method analogous to the method described above with reference to  FIGS. 5 to 10  as well as the process conditions set forth above can be employed in forming the second spacers  401  and  403 . 
     In one or more embodiments, there may be no specific limitations on the thickness or the height of the second spacers  401  and  403 . In one or more embodiments, the height of at least one of the second spacers  401  and  403  can be in a range from ¼ of the height of the semiconductor layer (s) in the associated fin (s) to the height of the semiconductor layer in the associated fin(s). The top of first spacer, which may be buried under the STI dielectric, should be close to the bottom of the channel area. In one or more embodiments, the fin above STI dielectric is more than ¼ of the height of the semiconductor layer in associated fin(s). In one or more embodiments, as illustrated in  FIG. 4 , the second spacers can be formed up to and can contact (and overlap) the two sides of the associated hard masks of the respective associated fins. In one or more embodiments, the second spacer can have a height in a range from 200 nm to 500 nm. 
     In one or more embodiments, the second spacers may directly contact the associated fins, as illustrated in  FIG. 4 . In one or more embodiments, there can be one or more intermediate layers, such as a native oxide layer and/or one or more other functional layers, between a second spacer and the associated fin. In one or more embodiments, the intermediate layer(s) may not adversely affect the stress effect exerted by the spacer on the associated fin. 
     According to some embodiments of the present invention, carrier mobility in respective desired portions (e.g. the portion below the channel formation region between the source and the drain) of the N-type device and/or P-type device can be minimized by the stress effect, and thus leakage between the source and the drain can be minimized. Additionally or alternatively, carrier mobility of the channel formation region can be enhanced, and thus device performance can be optimized. 
       FIG. 12  illustrates a perspective view of a semiconductor device in which a gate  1201  is formed after the forming of the insulating layer  301  illustrated in  FIG. 3  according to one or more embodiments of the present invention. After the formation of the insulating layer  301 , gate  1201  can be formed over the insulating layer  301  (and can also be formed over portions of the first spacer not covered by the insulating layer  301 ). The gate  1201  enwraps at least a portion of the fins. The gate  1201  may include features analogous to features of the above-described gate  1101 . In one or more embodiments, a source and a drain can be formed in the fins in a self-aligned manner, after the formation of the gate  1201 . 
     Thereafter, by means of a method analogous to that discussed with reference to  FIGS. 5 to 10 , a layer of tensile stress material  1301  and a layer of compressive stress material  1303  can be formed respectively in the N-type device part and in the P-type device part, over the insulating layer (and over portions of the first spacers not covered by the insulating layer), as illustrated in  FIG. 13 . Subsequently, the layer of tensile stress material  1301  and the layer of compressive stress material  1303  are etched so as to form the second spacers  401  and  403  illustrated in  FIG. 4 . 
     In one or more embodiments, the second spacers  401  and  403  may be formed after formation of the gate  1201  on the insulating layer  301 . In some embodiments, the gate can be formed on desired portions of the fins (such as the channel formation region) after the second spacers have been formed to exert stress for the fins and have been subsequently removed from the desired portions of the fins. 
     In one or more embodiments, as described above, at least an intermediate layer may be formed between at least one first spacer ( 201  and/or  203 ) and (the semiconductor layer) of at least one fin and/or between the first spacers ( 201  and  203 ) and the substrate. The method for manufacturing the semiconductor device may comprise a step of forming an intermediate layer on the sidewall of the at least one fin and/or on the surface of the substrate before forming the at least one first spacer. The first spacer may be subsequently formed. The intermediate layer may be disposed between the first spacer and the semiconductor layer and/or between the first spacer and the substrate surface. The intermediate layer may be formed on (and may contact) the sidewall of the fin and/or on the surface  110  of the substrate, and the first spacer may be formed on (and may contact) the intermediate layer. 
     In one or more embodiments, as described above, at least an intermediate layer can be formed between at least one second spacer ( 401  and/or  403 ) and at least one fin. The method for manufacturing the semiconductor device may comprise a step of forming an intermediate layer on the sidewall of the at least one fin before forming the at least one second spacer. The second spacer may be subsequently formed. The intermediate layer may be disposed between the second spacer and the semiconductor layer. The intermediate layer may be formed on (and may contact) the sidewall of the fin, and the second spacer may be formed on (and may contact) the intermediate layer. 
     Embodiments of the present invention have been described above with reference to the accompanying drawings. It should be understood that these embodiments are illustrative. The embodiments of the present invention can be combined and/or altered. One of ordinary skill in the art can make various modifications to the embodiments and details of the present invention based on the teachings of the present invention. All these modifications are within the spirit and scope defined by the attached claims.