Abstract:
Disclosed herein are methods for better variable height control of FinFET patterned fins. In one example, the method includes forming a layer on a substrate, patterning that layer to create trenches, and forming a common stack material in the trenches. Next, a pFET masking material is formed over a portion of the structure, and an nFET channel material is formed in the unmasked trenches. The pFET masking material is removed and an nFET masking material is formed over the portion of the structure that includes the nFET channel material, and a pFET channel material is formed in the unmasked trenches. Next, the unmasked patterned material is made flush with the pFET channel material, thereby creating a difference in height with the masked pattern material. Finally, the nFET masking material is removed and the patterned layer is recessed to expose pFET and nFET channel material fin structures of differing heights.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     Generally, the present invention relates to the manufacturing of sophisticated semiconductor devices, and, more specifically, to various methods of improved fabrication and variable height control of structures used in integrated circuit devices. 
     2. Description of the Related Art 
     The fabrication of advanced integrated circuits, such as CPU&#39;s, storage devices, ASIC&#39;s (application specific integrated circuits) and the like, requires the formation of a large number of circuit elements in a given chip area according to a specified circuit layout, wherein field effect transistors (NMOS and PMOS transistors) represent one important type of circuit element used in manufacturing such integrated circuit devices. A field effect transistor, irrespective of whether an NMOS transistor or a PMOS transistor is considered, typically comprises doped source and drain regions that are formed in a semiconducting substrate that are separated by a channel region. A gate insulation layer is positioned above the channel region and a conductive gate electrode is positioned above the gate insulation layer. By applying an appropriate voltage to the gate electrode, the channel region becomes conductive and current is allowed to flow from the source region to the drain region. 
     Numerous processing operations are performed in a very detailed sequence, or process flow, to form such integrated circuit devices, e.g., deposition processes, etching processes, heating processes, masking operations, etc. In general, the formation of integrated circuit devices involves, among other things, the formation of various layers of material and patterning or removing portions of those layers of material to define a desired structure, such as a gate electrode, a sidewall spacer, etc. Device designers have been very successful in improving the electrical performance capabilities of transistor devices, primarily by reducing the size of or “scaling” various components of the transistor, such as the gate length of the transistors. As size is reduced, the control of the height of fin structures on bulk substrates is difficult. Furthermore, existing methods make a CMOS flow difficult when attempting to use alternative channel materials for nFET and pFET. Conventional FinFET fin formation utilizes a hard mask and etching to etch away surrounding area, creating the fin. The trenches on each side of the fin are then filled with oxide, and excess oxide is removed with chemical mechanical planarization (CMP) and/or oxide etching. FinFET devices are currently only available in one height format. This does not allow the flexibility or control of device widths that is currently available to designers with planar CMOS structures. Active fin height is the dominant control of the effective FinFET device width. This means that device width can only be an integer multiplier of 1 fin “width” (height×2+width). In order to accommodate more granular device widths, various active fin heights or having different amounts of silicon (Si) exposed (active Si) above the oxide are necessary. 
     The present disclosure is directed to various methods of fabricating features in an integrated circuit structure, using an improved variable fin height control technique. These techniques can be used in CMOS circuits with alternative channel materials or traditional materials. 
     SUMMARY OF THE INVENTION 
     The following presents a simplified summary of the invention in order to provide a basic understanding of some aspects of the invention. This summary is not an exhaustive overview of the invention. It is not intended to identify key or critical elements of the invention or to delineate the scope of the invention. Its sole purpose is to present some concepts in a simplified form as a prelude to the more detailed description that is discussed later. 
     Generally, the present disclosure is directed to various methods for better variable height control of the FinFET patterned fins. In one example, the method includes forming a layer on a substrate, patterning that layer to create trenches, and then forming a common stack material in the trenches. Next, a pFET masking material is formed over a portion of the structure, and then an nFET channel material is formed in the unmasked trenches. The pFET masking material is then removed and an nFET masking material is formed over the portion of the structure that includes the nFET channel material. Next a pFET channel material is formed in the unmasked trenches. Next, the unmasked patterned material is made flush with the pFET channel material, thereby creating a difference in height with the masked pattern material. Finally the nFET masking material is removed and the patterned layer is recessed to expose pFET channel material and nFET channel material fin structures of differing heights. 
     In other illustrative examples the common stack material is formed on the substrate prior to forming the layer used to create trenches. In other embodiments the method includes the different step of controlling the variable fin height by epitaxial growth height. 
     One embodiment of this invention begins by depositing or growing an insulator, such as an oxide material, for example, silicon dioxide. This oxide material is then patterned and etched to open windows or trenches to the substrate where fins will be grown. If a common channel material (for example, Si:2% C) is desired, it is epitaxially grown in the windows. Then, some windows are covered and one pole of fins (for example nFET) are epitaxially grown in the exposed windows (with Si as an example). The previously masked windows are opened and the newly formed fins are masked. The alternate channel material is then grown (i.e., germanium (Ge) for pFETs). The fins are grown to two different heights. The masked fins are then un-masked and the silicon dioxide is recessed to allow the fins to protrude from the oxide at their different heights. The existing fin formation flow requires approximately 17 steps. This flow could require less than 12 steps. This invention also allows for different channel materials for NMOS and PMOS, or can also allow for different areas, such as logic and SRAM. Other embodiments of the invention can include masking areas of library cells. 
     This invention also allows the FinFET channels to be produced using different channel material (for example, Ge for pFET and Si for nFET). This invention is extendable to group III-V semiconductor materials. Instead of a Si substrate, an InP buffer could be used as the “substrate.” Some embodiments of this flow do not need a hard mask to etch the fins, which makes removal of the hard mask unnecessary. Initial oxide patterning can be done using various methods, such as conventional lithography, extreme ultraviolet lithography (EUV), or sidewall image transfer (SIT). This invention takes two primary paths to achieve variable height control for the fin devices. Silicon fins are currently created using an etch process. This invention allows for variable recess of the local isolation surrounding the fin structure. By controlling the recess amount, the amount of exposed fin may be tailored to different fin heights or effective device widths. An alternative method utilizes epitaxially grown fins. Silicon or alternative channel material can be selectively, epitaxially grown from the substrate forming fins. By masking some fin trenches, only a subset of fins may be grown at a time. Each subset (pFET vs. nFET, or similar channel vs. similar channel) can be grown to a specified height within the insulator trench. The insulator can then be blanket recessed to a uniform height with different fin heights exposed. Each subset of fins can also have the local isolation recessed independently of each other prior to removing the mask layers. Advantages of this invention include the ability to control fin height by groups. This allows for more variation of effective device widths, which is a great advantage to designers. This also allows for the use of high quality thermal oxide as a local isolation for epitaxially grown versions. The local isolation recess variation method included in this invention allows for integration with methods of etching the substrate to form the fins. This invention can also use alternative channel materials. 
     Another option is to introduce an initial difference in total Si fin height so that a uniform oxide recess exposes more Si for the taller fins than the shorter fins. This initial difference would be formed by etching some of the fins back prior to isolation oxide deposition. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The disclosure may be understood by reference to the following description taken in conjunction with the accompanying drawings, in which like reference numerals identify like elements, and in which: 
       In general,  FIGS. 1-54  show cross-sectional views of a structure going through various illustrative examples of fabrication steps of an improved process used in forming integrated circuit device structures, in accordance with embodiments of the present invention. 
       While the subject matter disclosed herein is susceptible to various modifications and alternative forms, specific embodiments thereof have been shown by way of example in the drawings and are herein described in detail. It should be understood, however, that the description herein of specific embodiments is not intended to limit the invention to the particular forms disclosed, but on the contrary, the intention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the invention as defined by the appended claims. 
     
    
    
     DETAILED DESCRIPTION 
     Various illustrative embodiments of the invention are described below. In the interest of clarity, not all features of an actual implementation are described in this specification. It will of course be appreciated that in the development of any such actual embodiment, numerous implementation-specific decisions must be made to achieve the developers&#39; specific goals, such as compliance with system-related and business-related constraints, which will vary from one implementation to another. Moreover, it will be appreciated that such a development effort might be complex and time-consuming, but would nevertheless be a routine undertaking for those of ordinary skill in the art having the benefit of this disclosure. 
     The present subject matter will be described with reference to the attached figures. Various structures, systems and devices are schematically depicted in the drawings for purposes of explanation only and so as to not obscure the present disclosure with details that are well known to those skilled in the art. Nevertheless, the attached drawings are included to describe and explain illustrative examples of the present disclosure. The words and phrases used herein should be understood and interpreted to have a meaning consistent with the understanding of those words and phrases by those skilled in the relevant art. No special definition of a term or phrase, i.e., a definition that is different from the ordinary and customary meaning as understood by those skilled in the art, is intended to be implied by consistent usage of the term or phrase herein. To the extent that a term or phrase is intended to have a special meaning, i.e., a meaning other than that understood by skilled artisans, such a special definition will be expressly set forth in the specification in a definitional manner that directly and unequivocally provides the special definition for the term or phrase. 
     The present disclosure is directed to various methods of controlling the height of various structures used in forming integrated circuit devices or in a semiconducting substrate. As will be readily apparent to those skilled in the art upon a complete reading of the present application, the present method is applicable to a variety of devices, including, but not limited to, ASICs, logic devices, memory devices, etc. Moreover, the present invention may be employed in forming any of a variety of different types of features formed on an integrated circuit product, such as lines, trenches, gate electrode structures, fins for FinFET devices, contact structures, back-end-of-line (BEOL) structures, etc. 
     Portions of the FinFET device structure are formed using well-known techniques and process steps (e.g., techniques and steps related to doping, photolithography and patterning, etching, material growth, material deposition, surface planarization and the like) that will not be described in detail here. Moreover, the various tasks and process steps described herein may be incorporated into a more comprehensive procedure or process having additional steps or functionality not described in detail herein. In particular, various steps in the manufacture of semiconductor-based transistors are well known and so, in the interest of brevity, many conventional steps will only be mentioned briefly herein or will be omitted entirely without providing the well-known process details. 
     The techniques and technologies described herein may be utilized to fabricate MOS transistor devices, including NMOS transistor devices, PMOS transistor devices and CMOS transistor devices. In particular, the process steps described herein can be utilized in conjunction with any semiconductor device fabrication process that forms gate structures for transistors. Although the term “MOS device” properly refers to a device having a metal gate electrode and an oxide gate insulator, that term may be used to refer to any semiconductor device that includes a conductive gate electrode (whether metal or other conductive material) that is positioned over a gate insulator (whether oxide or other insulator) which, in turn, is positioned over a semiconductor substrate. 
     Certain terminology may also be used in the following description for the purpose of reference only, and thus are not intended to be limiting. For example, terms such as “upper,” “lower,” “above” and “below” refer to directions in the drawings to which reference is made. Terms such as “front,” “back,” “rear,” “side,” “outboard” and “inboard” describe the orientation and/or location of portions of a feature or element within a consistent but arbitrary frame of reference which is made clear by reference to the text and the associated drawings describing the item under discussion. Such terminology may include the words specifically mentioned above, derivatives thereof, and words of similar import. Similarly, the terms “first,” “second” and other such numerical terms referring to structures do not imply a sequence or order unless clearly indicated by the context. With reference to the attached drawings, various illustrative embodiments of the methods and devices disclosed herein will now be described in more detail. 
     The figures illustrate versions where height is controlled by local isolation recess and where height is controlled by epitaxial growth height. It also depicts the use of a continuous common channel material and isolated common channel material. The present disclosure is directed to various methods of FinFET fabrication, and to FinFET devices. As will be readily apparent to those skilled in the art upon a complete reading of the present application, the present method is applicable to a variety of technologies, e.g., NMOS, PMOS, CMOS, etc., and is readily applicable to a variety of devices, including, but not limited to, logic devices, memory devices, etc. With reference to  FIGS. 1-54 , various illustrative embodiments of the methods disclosed herein will now be described in more detail. Additionally, the term “substrate” as used herein is intended to be very broad in nature and cover any type or structure or form of a channel region of a transistor that is commonly in contact with or positioned below a gate insulation layer, such as a layer of silicon/germanium that is commonly found in PMOS devices. The term “substrate” should also be understood to cover any of a variety of different semiconductor materials, such as silicon, silicon/germanium, gallium arsenide, etc. Instead of a silicon substrate, an InP buffer could be used as the substrate. 
       FIGS. 1-12  show cross-sectional views of a structure  100  going through fabrication steps of an improved FinFET fabrication process, in accordance with embodiments of the present invention. More specifically,  FIG. 1 , in one embodiment, shows a cross-sectional view of a semiconductor device  100  in an early manufacturing stage. With reference to  FIG. 1 , the improved FinFET process may start out with providing a semiconductor substrate  106 . The substrate  106  may have a variety of configurations, such as the depicted bulk silicon configuration. The substrate may also have a silicon-on-insulator (SOI) configuration that includes a bulk silicon layer, a buried insulation layer and an active layer, wherein semiconductor devices are formed in and above the active layer. Thus, the terms substrate or semiconductor substrate should be understood to cover all forms of semiconductor structures. The substrate may also be made of materials other than silicon. The substrate material  106  is preferably a silicon material as typically used in the semiconductor industry, e.g., relatively pure silicon, as well as silicon admixed with other elements, such as germanium, carbon and the like. 
     Next, with reference to  FIG. 2 , a material layer  108  is formed over the top of the substrate  106 . In one embodiment, the material layer  108  is an insulator. The material layer  108  may be oxide, such as SiO 2 , and may be formed by plasma enhanced atomic layer deposition (PEALD), low pressure chemical vapor deposition (LPCVD), chemical vapor deposition (CVD), thermally grown or deposited with other methods. 
     Next, with reference to  FIG. 3 , patterning of the material layer  108  ( FIG. 2 ) into at least one patterned material structure  110  is performed. The patterning may be performed by etching to define at least one trench  114  and a substrate top surface  112 . In one embodiment, the etching may be performed by plasma-based etching, leaving the at least one patterned material structure  110 , defining a trench width from 5-25 nm. 
     Next, with reference to  FIG. 4 , a common stack material  118  is formed in the at least one trench  114  over the substrate top surface  112 . In one embodiment, the common stack material  118  may be formed by epitaxially growing the common stack material  118 . The common stack material  118  may be Si—C, in the case of Si or SiGe channels, or could be InP in the case of group III-V semiconductor material channels. In one embodiment, the common stack material  118  may be 5-20 nm thick. 
     Next, with reference to  FIG. 5 , a first masking material  120  is formed on a first portion of the common stack material  118  and a first portion of the at least one patterned material structure  110  proximate to the first portion of the common stack  118 . In one embodiment, the first masking material  120  may be deposited. The first masking material  120  may be pFET masking material, such as Si 3 N 4 , TiN, SiO 2 , etc. The first portion of the common stack material  118  and the first portion of the at least one patterned material structure  110  proximate to the first portion of the common stack material may define a cell library. 
     Next, with reference to  FIG. 6 , a first channel material  122  is formed on a second portion of the common stack material  118 . In one embodiment, the first channel material  122  may be formed by epitaxially growing the first channel material  122 . The first channel material  122  may be nFET channel material, such as Si, or group III-V semiconductor material. In one embodiment, the first channel material  122  may be 20-100 nm thick. 
     Next, with reference to  FIG. 7 , removal of the first masking material  120  is performed. In one embodiment, the removal of the first masking material  120  may be performed by plasma-based processing or “wet” chemical methods. 
     Next, with reference to  FIG. 8 , a second masking material  124  is formed on the first channel material  122  and a second portion of the at least one patterned material structure  110  proximate to the first channel material  122 . In one embodiment, the second masking material  124  may be formed by depositing the second masking material  124 . In one embodiment, the second masking material  124  may be nFET masking material, such as Si 3 N 4 , TiN, SiO 2 , etc. The first channel material  122  and the portion of the at least one patterned material structure  110  proximate to the first channel material  122  may define a cell library. 
     Next, with reference to  FIG. 9 , a second channel material  126  is formed on the first portion of the common stack material  118 . In one embodiment, the second channel material  126  may be epitaxially grown. The second channel material  126  may be pFET channel material and as such may have a germanium (Ge) content, ranging from 25-100% and ranging from 20-100 nm thick. 
     Next, with reference to  FIG. 10 , a portion of the unmasked material is removed  136 , thereby producing an asymmetry between the various structure heights. The material removal may be performed by conventional plasma or wet etching methods. 
     Next, with reference to  FIG. 11 , removal of the second masking material  124  is performed. In one embodiment, the removal of the second masking material  124  may be performed by plasma-based processing or “wet” chemical methods. 
     Next, with reference to  FIG. 12 , recessing the at least one patterned material structure  110  is performed to produce recessed structure  130 , thereby producing an asymmetry between various recessed structure  130  heights  138 ,  140 . In one embodiment, the recessing may be performed by conventional plasma or wet etching methods. In one embodiment, the recessed structure  130  may result from having been recessed to a depth range of 5-40 nm. 
       FIGS. 13-24  show cross-sectional views of a structure  200  going through fabrication steps of an improved FinFET fabrication process, in accordance with embodiments of the present invention. More specifically,  FIG. 13 , in one embodiment, shows a cross-sectional view of a semiconductor device  200  in an early manufacturing stage. With reference to  FIG. 13 , the improved FinFET process may start out with providing a semiconductor substrate  206 . 
     Next, with reference to  FIG. 14 , a common stack layer  204  is formed over the substrate  206 . In one embodiment, the common stack layer  204  may be SiC in the case of Si or SiGe channels, or could be InP in the case of group III-V material channels, and may be formed by epitaxial growth or other deposition methods. In one embodiment, the common stack layer  204  may be 5-20 nm thick. 
     Next, with reference to  FIG. 15 , a material layer  208  is formed over the common stack layer  204 . In one embodiment, the material layer  208  may be silicon oxide or silicon nitride and may be formed by various depositing or growth methods. 
     Next, with reference to  FIG. 16 , patterning of the material layer  208  is performed to produce at least one patterned material structure  210 . The patterning may be performed by etching material layer  208  to define at least one trench  214  and a channel layer top surface  212 . In one embodiment, the etching may be performed by plasma-based processing, leaving the at least one patterned material  210 . 
     Next, with reference to  FIG. 17 , a first masking material  220  is formed on a first portion of the channel layer  204  and a first portion of the at least one patterned material structure  210 . In one embodiment, forming the first masking material  220  may be by depositing and patterning the first masking material  220 . The first masking material  220  may be pFET masking material, such as Si 3 N 4 , TiN, SiO 2 , etc. 
     Next, with reference to  FIG. 18 , a first channel material  222  is formed on a second portion of the common stack layer  204 . In one embodiment the first channel material  222  may be formed by epitaxially growing the first channel material  222 . The first channel material  222  may be nFET channel material, such as Si, or group III-V semiconductor material. In one embodiment, the first channel material  222  may be 20-100 nm thick. 
     Next, with reference to  FIG. 19 , removal of the first masking material  220  is performed. In one embodiment, removal of the first masking material  220  may be performed by “wet” chemical removal. 
     Next, with reference to  FIG. 20 , a second masking material  224  is formed on the first channel material  222  and a second portion of the at least one patterned material structure  210  proximate to the first channel material  222 . In one embodiment, the second masking material  224  is formed by depositing the second masking material  224 . In one embodiment, the second masking material  224  may be nFET masking material such as Si 3 N 4 , TiN, SiO 2 , etc. 
     Next, with reference to  FIG. 21 , a second channel material  226  is formed on the first portion of the common stack layer  204 . In one embodiment, the second channel material  226  may be epitaxially grown. The second channel material  226  may be pFET channel material and as such have a Ge content ranging from 25-100%. In one embodiment, the second channel material  226  may be 15-35 nm thick. 
     Next, with reference to  FIG. 22 , a portion of the unmasked material is removed, thereby producing an asymmetry between the various structure heights  236 . The material removal may be performed by conventional plasma or wet etching methods. 
     Next, with reference to  FIG. 23 , removal of the second masking material  224  is performed. In one embodiment, the removal of the second masking material  224  may be performed by “wet” chemical removal. 
     Next, with reference to  FIG. 24 , recessing of the at least one patterned material structure  210  is performed to produce recessed structure  230 , thereby producing an asymmetry between various recessed structure  230  heights  238 ,  240 . In one embodiment, the recessing may be performed by conventional plasma or wet etching methods. In one embodiment, the recessed structure may be produced by recessing the patterned material  210  to a depth range of 5-40 nm. 
       FIGS. 25-32  show cross-sectional views of a structure  300  going through fabrication steps of an improved FinFET fabrication process, in accordance with embodiments of the present invention. More specifically,  FIG. 25 , in one embodiment, shows a cross-sectional view of a semiconductor device  300  in an early manufacturing stage. With reference to  FIG. 25 , the improved FinFET process may start out with providing a semiconductor substrate  306 . 
     Next, with reference to  FIG. 26 , one or more fins  310  are formed in the substrate  306 . The fins  310  may be formed by patterning and etching the substrate  306 . A first masking material  318  is formed and patterned on the substrate  306  and remains on the fins  310  after fin formation. At least one trench  314  is defined when forming the fins  310 . In one embodiment, the first masking material  318  may be Si 3 N 4 , SiO2 or any dielectric with good etch contrast to the channel material (Si, SiGe, III-V, etc.). 
     Next, with reference to  FIG. 27 , a material layer  320  is formed in the at least one trench  314 . The material layer  320  may be formed above  336  the first masking material  318  and in one embodiment to a height of 0 (bottom up fill) to 50 nm. In one embodiment, the material layer  320  may be formed by ALD, CVD, spin-on, etc. and may be an insulator, with SiO 2  preferred. 
     Next, with reference to  FIG. 28 , a second masking material  324  is formed on a first portion of the material layer  320 . In one embodiment, the second masking material  324  may be formed by depositing and patterning the second mask material  324 . The second masking material  324  may be TiN, SiN, photoresist, organic planarizing layer (OPL), aC, or SiO 2 . 
     Next, with reference to  FIG. 29 , a portion of the material layer  320  that is not covered by the second masking material  324  is removed, thereby producing an asymmetry across the height  338  of the material layer  320 . The material removal may be performed by conventional plasma or wet etching methods. 
     Next, with reference to  FIG. 30 , removal of the second masking material  324  is performed. In one embodiment, the removal of the second masking material  324  may be performed by conventional plasma or wet etching. 
     Next, with reference to  FIG. 31 , recessing the material layer  320  is performed to produce recessed structure  330 , thereby producing an asymmetry between various recessed structure  330  heights  340 ,  342 . In one embodiment, the recessing may be performed by conventional plasma or wet etching methods. In one embodiment, the recessed structure height may be the result of recessing by 10-50 nm. 
     Next, with reference to  FIG. 32 , removal of the first masking material  318  is performed. In one embodiment, the removal of the first masking material  318  may be performed by conventional plasma or wet etching methods. 
       FIGS. 33-43  show cross-sectional views of a structure  400  going through fabrication steps of an improved FinFET fabrication process, in accordance with embodiments of the present invention. More specifically,  FIG. 33 , in one embodiment, shows a cross-sectional view of a semiconductor device  400  in an early manufacturing stage. With reference to  FIG. 33 , the improved FinFET process may start out with providing a semiconductor substrate  406 . 
     Next, with reference to  FIG. 34 , a material layer  408  is formed over the substrate  406 . In one embodiment, the material layer  408  may be insulator, such as an oxide, SiO 2 , and may be formed by deposition or thermal oxidation methods. 
     Next, with reference to  FIG. 35 , patterning the material layer  408  into at least one patterned material structure  410  is performed. Patterning the material layer  408  may be performed by etching material layer  408  to define at least one trench  414 . In one embodiment, the etching may be performed by plasma-based processing, leaving the at least one patterned material structure  410 . 
     Next, with reference to  FIG. 36 , a common stack material  418  is formed in the at least one trench  414 . In one embodiment, the common stack material  418  may be SiC, uniquely doped Si, etc., and may be formed by deposition techniques or epitaxially grown. In one embodiment, the common stack material  418  may be 5-20 nm thick. 
     Next, with reference to  FIG. 37 , a first masking material  420  is formed on a first portion of the channel material  418  and a first portion of the at least one patterned material structure  410 . In one embodiment, forming the first masking material  420  may include depositing and patterning the first masking material  420 . The first masking material  420  can be a pFET masking material, such as Si 3 N 4 , TiN, SiO 2 , etc. 
     Next, with reference to  FIG. 38 , a first channel material  422  is formed on a second portion of the common stack material  418 . In one embodiment, the first channel material  422  may be formed by epitaxially growing the first channel material  422 . The first channel material  422  may be an nFET channel material, such as Si, uniquely doped Si, etc. In one embodiment, the first channel material  422  may be 40-60 nm thick. 
     Next, with reference to  FIG. 39 , removal of the first masking material  420  is performed. In one embodiment, the removal may be performed by “wet” chemical removal methods. 
     Next, with reference to  FIG. 40 , a second masking material  424  is formed on the first channel material  422  and a second portion of the at least one patterned material structure  410  proximate to the first channel material  422 . In one embodiment, forming the second masking material  424  may be performed by depositing and patterning the second masking material  424 . In one embodiment, the second masking material  424  may be nFET masking material such as Si 3 N 4 , TiN, SiO 2 , etc. 
     Next, with reference to  FIG. 41 , a second channel material  426  is formed on the first portion of the common stack material  418  and the second channel material  426  is formed to a height different than the height of the first channel material  422 . In one embodiment, the second channel material  426  may be epitaxially grown. The second channel material  426  may be a pFET channel material and have a Ge content ranging from 25-100%. In one embodiment, the second channel material  426  may be 40-60 nm thick. 
     Next, with reference to  FIG. 42 , removal of the second masking material  424  is performed. In one embodiment, the removal of the second masking material  424  may be performed by “wet” chemical etching methods. 
     Next, with reference to  FIG. 43 , recessing of the at least one patterned material structure  410  is performed to produce recessed structure  430 . In one embodiment, the recessing may be performed by plasma-based processing, sublimation-based methods or “wet” chemical etching methods. In one embodiment, the recessed structure  430  may be produced by recessing the at least one patterned material structure  410  to a depth range of 25-40 nm. 
       FIGS. 44-54  show cross-sectional views of a structure  500  going through fabrication steps of an improved FinFET fabrication process, in accordance with embodiments of the present invention. More specifically,  FIG. 44 , in one embodiment, shows a cross-sectional view of a semiconductor device  500  in an early manufacturing stage. With reference to  FIG. 44 , the improved FinFET process may start out with providing a semiconductor substrate  506 . 
     Next, with reference to  FIG. 45 , a common stack layer  504  is formed over the substrate  506 . In one embodiment, the common stack layer  504  may be SiC, uniquely doped Si, etc., and may be formed by deposition techniques or epitaxially grown. In one embodiment, the common stack layer  504  may be 5-20 nm thick. 
     Next, with reference to  FIG. 46 , a material layer  508  is formed over the common stack layer  504 . In one embodiment, the material layer  508  may be oxide, nitride, etc., and may be formed by deposition methods. 
     Next, with reference to  FIG. 47 , patterning the material layer  508  into at least one patterned material structure  510  is performed. The patterning may be performed by etching material layer  508  to define at least one trench  514  and a channel layer top surface  512 . In one embodiment, the etching may be performed by plasma-based processing, leaving the patterned material  510 . 
     Next, with reference to  FIG. 48 , a first masking material  520  is formed on a first portion of the common stack layer  504  and a first portion of the at least one patterned material structure  510  proximate the first portion of the common stack layer  504 . In one embodiment, forming of the first masking material  520  may include depositing and patterning the first masking material  520 . The first masking material  520  may be a pFET masking material, for example Si 3 N 4 , TiN, SiO 2 , etc. 
     Next, with reference to  FIG. 49 , a first channel material  522  is formed on a second portion of the common stack layer  504 . In one embodiment, the first channel material  522  may be formed by epitaxially growing the first channel material  522 . The first channel material  522  may be an nFET channel material, for example Si, uniquely doped Si, etc. In one embodiment, the first channel material  522  may be 40-60 nm thick. 
     Next, with reference to  FIG. 50 , removal of the first masking material  520  is performed. In one embodiment, removal may be performed by “wet” chemical methods. 
     Next, with reference to  FIG. 51 , a second masking material  524  is formed on the first channel material  522  and a second portion of the at least one patterned material structure  510  proximate to the first channel material  522 . In one embodiment, forming the second masking material  524  may be performed by depositing and patterning the second masking material  524 . In one embodiment, the masking material  524  may be an nFET masking material, such as Si 3 N 4 , TiN, SiO 2 , etc. 
     Next, with reference to  FIG. 52 , a second channel material  526  is formed on the first portion of the common stack layer  504 . The second channel material  526  is formed to a height different from that of the first channel material  522 . In one embodiment, forming the second channel material  526  may be performed by epitaxially growing the second channel material  526 . The second channel material  526  may be a pFET channel material and, for example, have a Ge content in the range of 25-100%. In one embodiment, the second channel material  526  may be 40-60 nm thick. 
     Next, with reference to  FIG. 53 , removal of the second masking material  524  is performed. In one embodiment, removal of the second masking material  524  may be performed by “wet” chemical etching methods. 
     Next, with reference to  FIG. 54 , recessing the at least one patterned material structure  510  is performed to produce recessed structure  530 , thereby producing an asymmetry between various recessed structure  526  and  522  heights  540 . In one embodiment, the recessing may be performed by conventional plasma or wet etching methods. In one embodiment, recessed structure  530  may be produced by recessing the patterned material  510  to a depth range of 25-40 nm. 
     The particular embodiments disclosed above are illustrative only, as the invention may be modified and practiced in different but equivalent manners apparent to those skilled in the art having the benefit of the teachings herein. For example, the process steps set forth above may be performed in a different order. Furthermore, no limitations are intended to the details of construction or design herein shown, other than as described in the claims below. It is, therefore, evident that the particular embodiments disclosed above may be altered or modified and all such variations are considered within the scope and spirit of the invention. 
     While at least one exemplary embodiment has been presented in the foregoing detailed description, it should be appreciated that a vast number of variations exist. It should also be appreciated that the exemplary embodiment or embodiments described herein are not intended to limit the scope, applicability or configuration of the claimed subject matter in any way. Rather, the foregoing detailed description will provide those skilled in the art with a convenient road map for implementing the described embodiment or embodiments. It should be understood that various changes can be made in the function and arrangement of elements without departing from the scope defined by the claims, which includes known equivalents and foreseeable equivalents at the time of filing this patent application. Accordingly, the protection sought herein is as set forth in the claims below.