Abstract:
Apparatus and related fabrication methods are provided for semiconductor device structures having encapsulated isolation regions. An exemplary method for fabricating a semiconductor device structure involves the steps of forming an isolation region of a first dielectric material in the semiconductor substrate adjacent to a first region of the semiconductor material, forming a first layer of a second dielectric material overlying the isolation region and the first region, and removing the second dielectric material overlying the first region leaving portions of the second dielectric material overlying the isolation region intact. The isolation region is recessed relative to the first region, and the second dielectric material is more resistant to an etchant than the first dielectric material.

Description:
TECHNICAL FIELD 
     Embodiments of the subject matter generally relate to semiconductor device structures and related fabrication methods, and more particularly, embodiments of the subject matter relate to devices formed on electrically isolated regions of semiconductor material and related fabrication methods. 
     BACKGROUND 
     Transistors, such as metal oxide semiconductor field-effect transistors (MOSFETs), are the core building block of the vast majority of semiconductor devices. Some semiconductor devices, such as high performance processor devices, can include millions of transistors. For such devices, decreasing transistors size, and thus increasing transistor density, has traditionally been a high priority in the semiconductor manufacturing industry. Increasing density necessarily involves reducing the area between neighboring devices, which in turn, requires reliable isolation between devices to prevent leakage currents, parasitic capacitances, and other undesirable electrical effects that may degrade performance and/or reduce yield. 
     BRIEF SUMMARY 
     A method is provided for fabricating a semiconductor device on a semiconductor substrate of a semiconductor material. The method involves the steps of forming an isolation region of a first dielectric material in the semiconductor substrate adjacent to a first region of the semiconductor material, forming a first layer of a second dielectric material overlying the isolation region and the first region, and removing the second dielectric material overlying the first region leaving portions of the second dielectric material overlying the isolation region intact. The isolation region is recessed relative to the first region, and the second dielectric material is more resistant to an etchant than the first dielectric material. 
     In another embodiment, a method of fabricating a semiconductor device structure on a semiconductor substrate of a semiconductor material involves the steps of forming an oxide isolation region adjacent to a first region of the semiconductor material, conformably depositing a nitride material overlying the first region and the oxide isolation region, and removing the nitride material overlying the first region leaving a portion of the nitride material overlying the oxide isolation region intact. The oxide isolation region is recessed relative to the first region. 
     In another embodiment, another apparatus for a semiconductor device is provided. The semiconductor device includes an active region of semiconductor material having a transistor structure formed thereon, an oxide isolation region adjacent to the active region of semiconductor material, the oxide isolation region being recessed relative to the active region, and a dielectric capping material overlying the oxide isolation region. The dielectric capping material is more resistant to an etchant than the oxide isolation region. 
     This summary is provided to introduce a selection of concepts in a simplified form that are further described below in the detailed description. This summary is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to be used as an aid in determining the scope of the claimed subject matter. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       A more complete understanding of the subject matter may be derived by referring to the detailed description and claims when considered in conjunction with the following figures, wherein like reference numbers refer to similar elements throughout the figures. 
         FIGS. 1-7  are cross-sectional views that illustrate a semiconductor device structure and methods for fabricating the semiconductor device structure in exemplary embodiments. 
     
    
    
     DETAILED DESCRIPTION 
     The following detailed description is merely illustrative in nature and is not intended to limit the embodiments of the subject matter or the application and uses of such embodiments. As used herein, the word “exemplary” means “serving as an example, instance, or illustration.” Any implementation described herein as exemplary is not necessarily to be construed as preferred or advantageous over other implementations. Furthermore, there is no intention to be bound by any expressed or implied theory presented in the preceding technical field, background, brief summary or the following detailed description. 
     Techniques and technologies described herein may be utilized to fabricate MOS transistor devices on electrically isolated regions of a semiconductor substrate. Although the term “MOS device” properly refers to a device having a metal gate electrode and an oxide gate insulator, that term will be used throughout 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. Various steps in the fabrication of semiconductor devices 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. 
       FIGS. 1-7  illustrate a semiconductor device structure  100  and process steps for fabricating the same. Referring now to  FIGS. 1-2 , in an exemplary embodiment, fabrication of the semiconductor device structure  100  begins by providing an appropriate substrate of semiconductor material  102  and forming oxide isolation regions  104 ,  106  in the semiconductor substrate  102  to obtain electrically isolated regions  108 ,  110 ,  112  of semiconductor material  102 . As described in greater detail below, the electrically isolated regions  108 ,  110 ,  112  may be doped in a conventional manner and utilized to form electrically isolated transistor devices or other devices. Accordingly, for convenience, but without limitation, the electrically isolated regions  108 ,  110 ,  112  may alternatively be referred to herein as active regions. 
     In an exemplary embodiment, the semiconductor substrate  102  is realized as a bulk semiconductor substrate comprising a silicon material, wherein the term “silicon material” is used herein to encompass the relatively pure silicon materials typically used in the semiconductor industry as well as silicon admixed with other elements such as germanium, carbon, and the like. Alternatively, the semiconductor material  102  can be realized as germanium, gallium arsenide, and the like, or the semiconductor material  102  can include layers of different semiconductor materials. Additionally, it should be noted that although the fabrication process may be described herein in the context of a bulk semiconductor substrate, the subject matter is not intended to be limited to bulk semiconductor substrates, and in practice, the fabrication process may utilize a silicon-on-insulator (SOI) substrate in an equivalent manner with corresponding modifications to the relative dimensions described below to accommodate the thickness of the silicon of the SOI substrate. 
     In an exemplary embodiment, the electrically isolated regions  108 ,  110 ,  112  are formed by performing shallow trench isolation (STI) on the semiconductor substrate. In the illustrated embodiment, a layer of oxide material  114  (alternatively referred to herein as the pad oxide) is formed overlying the semiconductor material  102 , and a layer of masking material  116  is formed overlying the oxide material  114 . In an exemplary embodiment, the layer of oxide material  114  is relatively thin, typically less than about 10 nanometers (nm) and preferably around 5 nm or less, and the oxide material  114  may be thermally grown or deposited on the exposed surfaces of the semiconductor substrate  102  in a conventional manner. The layer of masking material  116  is formed by conformably depositing a hard mask material, such as a nitride material (e.g., silicon nitride, silicon oxynitride, or the like) overlying the layer of oxide material  114  to a thickness in the range of about 80 nm. A nitride material, such as silicon nitride, is preferable because it accommodates the selective etching of underlying semiconductor material  102  when subsequently used as an etch mask. Accordingly, the portions of the masking material  116  overlying the active regions  108 ,  110 ,  112  may hereinafter be referred to for convenience, but without limitation, as the pad nitride. The pad nitride  116  is patterned to mask the desired active regions  108 ,  110 ,  112  of semiconductor material  102 , and an anisotropic etchant is utilized to remove exposed (or unprotected) portions of the pad oxide  114  and the semiconductor material  102  to form trenches between the active regions  108 ,  110 ,  112 . Although not illustrated in  FIG. 1 , the trenches may be formed about the perimeters of the active regions  108 ,  110 ,  112  or otherwise circumscribe the active regions  108 ,  110 ,  112  to physically isolate neighboring active regions  108 ,  110 ,  112 . The trenches are etched to a depth that exceeds the depth of any body regions (or well regions) subsequently formed in the active regions  108 ,  110 ,  112 . For example, in accordance with one embodiment, the trenches are etched to a depth of about 300 nm relative to the upper surface of the semiconductor material  102 . 
     After forming trenches, in an exemplary embodiment, a layer of oxide material  118  is formed on exposed surfaces of semiconductor material  102  in the trenches. For example, the oxide material  118  may be thermally grown on the exposed surfaces of the trenches by exposing the semiconductor substrate  102  to an oxidizing ambient at an elevated temperature that promotes selective growth of oxide material, such as silicon dioxide, on the exposed surfaces of the semiconductor material  102 . In an exemplary embodiment, the layer of oxide material  118  is relatively thin, and preferably, is formed to a thickness of about 5 nm or less. In one embodiment, the thickness of the oxide material  118  is within the range of about 3 nm to 4 nm. 
     After forming the layer of oxide material  118  in the trenches, the fabrication process continues by forming a second layer of oxide material  120  in the trenches and overlying the semiconductor substrate  102 , resulting in the semiconductor device structure  100  illustrated in  FIG. 1 . The second layer of oxide material  120  is preferably formed by conformably depositing an oxide material, such as silicon dioxide, using a plasma enhanced chemical vapor deposition (PECVD) process or another suitable deposition process. In this regard, the oxide material  120  may be realized as high aspect ratio plasma (HARP) oxide. In an exemplary embodiment, the oxide material  120  is deposited to a thickness that is greater than or equal to the depth of the trenches and is subsequently reduced to a height below the upper surfaces of the semiconductor material  102  of the active regions  108 ,  110 ,  112 , as described in greater detail below. For example, in accordance with one embodiment, the trenches are etched to a depth of about 300 nm relative to the surface of the semiconductor material  102 , and the thickness of the layer of oxide material  120  is within the range of about 300 nm to about 500 nm. In alternative embodiments, however, the oxide material  120  may be deposited to a thickness that is less than the depth of the trenches. For example, in accordance with one alternative embodiment, the trenches are etched to a depth of about 300 nm relative to the surface of the semiconductor material  102 , and the thickness of the layer of oxide material  120  is within the range of about 250 nm to about 300 nm. 
     After forming the oxide materials  118 ,  120  in the trenches, the fabrication process continues by removing portions of the oxide material  120  overlying the active regions  108 ,  110 ,  112 , resulting in the semiconductor device structure  100  of  FIG. 2 . In an exemplary embodiment, the fabrication process polishes the oxide material  120  to remove portions of the oxide material  120  across the semiconductor substrate  102  until reaching the upper surfaces of the pad nitride  116 . In accordance with one embodiment, chemical-mechanical planarization (CMP) is used to polish the oxide material  120  with a chemical slurry for a predetermined amount of time such that the CMP stops when the upper surfaces of the pad nitride  116  are exposed. In other words, the fabrication process ceases planarizing the oxide material  120  when the pad nitride  116  is reached. In this manner, the portions of the oxide material  120  overlying the active regions  108 ,  110 ,  112  are uniformly removed until the upper surfaces of the underlying pad nitride  116  are exposed. The remaining portions of oxide material  118 ,  120  in the trenches between the active regions  108 ,  110 ,  112  provide the oxide isolation regions  104 ,  106  that electrically isolate neighboring active regions  108 ,  110 ,  112 . 
     As illustrated in  FIG. 2 , in an exemplary embodiment, the oxide isolation regions  104 ,  106  are recessed relative to the active regions  108 ,  110 ,  112  by a depth (d) corresponding to the distance between the upper surfaces of the oxide material  120  in the trenches and the upper surfaces of the semiconductor material  102  of the active regions  108 ,  110 ,  112 . In an exemplary embodiment, the distance (d) between the upper surfaces of the oxide material  120  and the upper surfaces of the semiconductor material  102  is within the range of about five percent to about twenty percent of the depth of the trench. For example, in accordance with one embodiment, the trenches are etched to a depth of about 300 nm relative to the surface of the semiconductor material  102 , and the distance (d) between the upper surfaces of the oxide material  120  and the upper surfaces of the semiconductor material  102  is within the range of about 20 nm to about 50 nm. In this regard, if the thickness of the layer of oxide material  120  exceeds the thickness of the trenches such that distance between the upper surfaces of the oxide material  120  in the trenches after the CMP process and the upper surfaces of the semiconductor material  102  is less than the desired distance (d), an additional etch process step may be performed after the CMP to reduce the height of the oxide material  120  in the trenches and provide the desired distance (d) between the upper surfaces of the oxide material  120  and the upper surfaces of the semiconductor material  102 . For example, in accordance with one or more embodiments, after performing CMP to remove the oxide material  120  overlying the active regions  108 ,  110 ,  112 , excess oxide material  120  in the trenches is removed by performing an anisotropic etch process to remove portions of the oxide material  120  in the trenches to provide the desired recessed depth (d) of the oxide isolation regions  104 ,  106  relative to the active regions  108 ,  110 ,  112 . For example, plasma-based RIE may be performed using an anisotropic etchant that anisotropically etches the oxide material  120  with good selectivity to the pad nitride  116  until the distance between the upper surfaces of the oxide material  120  and the upper surfaces of the semiconductor material  102  is within the range of about five percent to about twenty percent of the depth of the trench. In this regard, the etch process step may be performed without any masking or other photolithography steps, as the remaining pad nitride  116  protects the underlying semiconductor material  102  of the active regions  108 ,  110 ,  112  from exposure to the etchant while portions of the oxide material  120  are removed. In other embodiments, the CMP process used to remove portions of the oxide material  120  overlying the active regions  108 ,  110 ,  112  may be modified to concurrently remove portions of the oxide material  120  in the trenches at a rate that provides the desired depth (d) relative to the upper surfaces of the semiconductor material  102 . 
     Referring now to  FIG. 3 , in an exemplary embodiment, the fabrication process continues by removing the pad nitride  116 , forming a layer of dielectric material  122  overlying the active regions  108 ,  110 ,  112  and the isolation regions  104 ,  106 , and forming another layer of dielectric material  124  overlying the layer of dielectric material  122 . In an exemplary embodiment, the layer of dielectric material  122  is realized as a layer of an oxide material, such as silicon dioxide, that is conformably deposited overlying the semiconductor device structure  100  of  FIG. 1 , for example, by using a low-pressure chemical vapor deposition (LPCVD) process or another suitable deposition process. For convenience, but without limitation, the dielectric material  122  may be referred to herein as an oxide material. The thickness of the oxide material  122  is less than the recessed depth (d) of the upper surfaces of the isolation regions  104 ,  106  relative to the upper surfaces of the active regions  108 ,  110 ,  112 , and is preferably less than about twenty-five percent of the recessed depth (d) of the isolation regions  104 ,  106 . For example, in accordance with one embodiment, the distance (d) between the upper surfaces of the oxide material  120  and the upper surfaces of the semiconductor material  102  is within the range of about 20 nm to about 50 nm, and the thickness of the oxide material  122  is about 5 nm or less. Preferably, the layer of oxide material  122  is as thin as possible, as described in greater detail below. 
     In an exemplary embodiment, the dielectric material  124  is realized as a material that is more resistant to one or more etchants than the oxide material  118 ,  120  of the isolation regions  104 ,  106 . In an exemplary embodiment, the dielectric material  124  is more resistant to hydrofluoric acid and/or hydrofluoric acid-comprising etchants than the oxide material  118 ,  120  of the isolation regions  104 ,  106 , that is, hydrofluoric acid etches the dielectric material  124  at a reduced rate relative to the oxide material  118 ,  120 . In an exemplary embodiment, the hydrofluoric acid resistant dielectric material  124  is realized as a nitride material, such as silicon nitride. It should be noted that other materials having the same general properties and characteristics could be used as the hydrofluoric acid resistant dielectric material  124  in lieu of silicon nitride. That said, silicon nitride is commonly used for other purposes in semiconductor manufacturing processes, is accepted for use in the industry, and is well documented. Accordingly, preferred embodiments employ silicon nitride for the hydrofluoric acid resistant dielectric material  124 , and the hydrofluoric acid resistant dielectric material  124  may alternatively be referred to herein as a nitride material. In the illustrated embodiment, after forming the layer of oxide material  122 , the layer of nitride material  124  is formed by conformably depositing silicon nitride overlying the oxide material  122  using an LPCVD process or another suitable deposition process. As described in greater detail below, the nitride material  124  functions as a capping material that encapsulates the upper surface of the oxide isolation regions  104 ,  106  and protects the oxide material  118 ,  120  from exposure to hydrofluoric acid and/or other etchant chemistries that may otherwise remove the oxide material  118 ,  120 . In this regard, the deposited thickness of the nitride material  124  is greater than the recessed depth (d) of the isolation regions  104 ,  106  relative to the semiconductor material  102  of the active regions  108 ,  110 ,  112 . In an exemplary embodiment, the thickness of the nitride material  124  is at least twice the recessed depth (d) of the isolation regions  104 ,  106  relative to the upper surfaces of the semiconductor material  102  of the active regions  108 ,  110 ,  112  (e.g., a thickness of the nitride material  124  of 2d). For example, in accordance with one embodiment, the distance (d) between the upper surfaces of the oxide material  120  and the upper surfaces of the semiconductor material  102  is within the range of about 20 nm to about 50 nm and the thickness of the nitride material  124  is within the range of about 40 nm to about 100 nm. As described in greater detail below, after subsequent process steps, the nitride material  124  overlying the isolation regions  104 ,  106  is preferably reduced to a thickness substantially equal to the recessed depth (d) of the isolation regions  104 ,  106 . 
     Referring now to  FIG. 4 , in accordance with one or more embodiments, the fabrication process continues by masking portions of the nitride material  124  overlying the isolation regions  104 ,  106  and removing portions of the layer of nitride material  124  overlying any large active regions. In this regard, a large active region should be understood as referring to an electrically isolated region of semiconductor material  102  having an area of about 400 square microns or more. For example, in the illustrated embodiment, the semiconductor device structure  100  includes a large active region  112  that may be utilized for fabricating thereon multiple transistor devices that do not need isolation, a transistor device that is larger than those fabricated on active regions  108 ,  110 , or another component, such as a MOS capacitor, a diode, or the like. As illustrated in  FIG. 3 , in practice, the conformal deposition of the nitride material  124  may be non-uniform by virtue of the topographical variations between small active regions  108 ,  110  and large active regions  112 , resulting in the portions of the nitride material  124  overlying the large active region  112  being thicker than the nitride material  124  overlying the smaller active regions  108 ,  110 . In this regard, reducing the thickness of the nitride material  124  overlying the large active region  112  may improve subsequent process steps, such as the planarization of the nitride material  124  described below. To remove portions of the nitride material  124 , a masking material  126  is formed overlying the semiconductor device structure  100  of  FIG. 3  and patterned to define an etch mask  128  that exposes portions of the nitride material  124  overlying the large active region  112 . In this regard, the portions of the masking material  126  overlying the isolation regions  104 ,  106  and the relatively smaller active regions  108 ,  110  remain intact. As illustrated, in an exemplary embodiment, portions of the masking material  126  that overlie portions of the large active region  112  adjacent to or otherwise bordering the isolation region  106  remain intact such that the mask  128  overlaps the periphery of the large active region  112  to ensure that any portions of the nitride material  124  overlying the adjacent isolation region  106  are not removed when the nitride material  124  overlying the large active region  112  is removed. After forming the mask  128 , the exposed portions of the nitride material  124  are removed by performing RIE to anisotropically etch the exposed nitride material  124  with an anisotropic etchant chemistry using the etch mask  128 . As illustrated in  FIG. 4 , in an exemplary embodiment, the exposed nitride material  124  overlying the large active region  112  is etched until the upper surface of the exposed nitride material  124  overlying the large active region  112  is substantially aligned with the upper surfaces of the nitride material  124  overlying the isolation regions  104 ,  106 . In this regard, variations in the thickness of the nitride material  124  relative to the upper surfaces of the semiconductor material  102  that may result from the conformal deposition on large areas (e.g., active region  112 ) relative to smaller areas (e.g., active regions  108 ,  110 ) may be reduced. After removing portions of the exposed nitride material  124  overlying the large active region  112  such that the nitride material  124  overlying the active region  112  is substantially aligned with the nitride material  124  overlying the isolation regions  104 ,  106 , any remaining masking material  126  is removed. 
     Referring now to  FIGS. 5-6 , in an exemplary embodiment, the fabrication process continues by removing portions of the nitride material  124  to obtain a substantially planar surface  130  that is aligned with the upper surface of the oxide material  122 , resulting in the semiconductor device structure  100  illustrated by  FIG. 5 . In an exemplary embodiment, the fabrication process planarizes the nitride material  124  to remove portions of the nitride material  124  across the semiconductor substrate  102  until reaching the upper surface of the oxide material  122 . In other words, the fabrication process ceases planarizing the nitride material  124  when the upper surfaces of the oxide material  122  are exposed. In accordance with one embodiment, CMP is used to polish the nitride material  124  with a chemical slurry for a predetermined amount of time such that the CMP stops when the upper surfaces of the oxide material  122  are exposed. As illustrated in  FIG. 5 , when the upper surfaces of the oxide material  122  are exposed, the nitride material  124  is completely removed from the active regions  108 ,  110 ,  112 , while portions of the nitride material  124  overlying the isolation regions  104 ,  106  remain intact and provide hydrofluoric acid resistant caps  132 ,  134  that encapsulate the upper surfaces of the oxide isolation regions  104 ,  106 . 
     After removing the nitride material  124  overlying the active regions  108 ,  110 , the fabrication process continues by removing exposed portions of the oxide material  122  and the pad oxide  114  overlying the active regions  108 ,  110 ,  112  to obtain the semiconductor device structure  100  illustrated by  FIG. 6 . In an exemplary embodiment, a diluted hydrofluoric acid etching process or another known etching process is performed to remove exposed oxide material  114 ,  122  until the upper surfaces of the semiconductor material  102  of the active regions  108 ,  110 ,  112  are exposed. In this regard, the nitride material  124  of the hydrofluoric acid resistant caps  132 ,  134  protects the underlying oxide material  118 ,  120 ,  122  from the etchant while the oxide material  114 ,  122  is removed from the active regions  108 ,  110 ,  112 . 
     By virtue of the layer of oxide material  122  being relatively thin (e.g., about 5 nm or less) in addition to the pad oxide  114  being relatively thin (e.g., about 5 nm or less), the difference between the upper surfaces of the nitride caps  132 ,  134  relative to the upper surfaces of the surrounding semiconductor material  102  of the active regions  108 ,  110 ,  112  is relatively small and corresponds to the combined thicknesses of the oxide layer  122  and the pad oxide  114  (e.g., about 10 nm or less), thereby reducing the topographical variations across the semiconductor substrate  102 . Thus, reducing the thickness of the oxide layer  122  and/or pad oxide  114  results in upper surfaces of the nitride caps  132 ,  134  that are more closely aligned with the upper surfaces of the active regions  108 ,  110 ,  112 , and accordingly, in exemplary embodiments, the oxide layer  122  is as thin as possible. The pad oxide  114  is also preferably as thin as possible; however, it will be appreciated that the thickness of the pad oxide  114  may be constrained by other process steps (e.g., the process steps for etching the trenches for the isolation regions  104 ,  106 ). It should be noted that in embodiments where it is desirable to provide a highly planar surface across the semiconductor substrate, the fabrication process may continue by performing one or more etch steps or planarization steps to reduce the height of the nitride caps  132 ,  134  until they are substantially aligned with the adjacent semiconductor material  102  of the active regions  108 ,  110 ,  112 . 
     Referring now to  FIG. 7 , although one or more additional process steps may be performed next, in the illustrated embodiment, transistor structures  140 ,  142  are formed on the smaller active regions  108 ,  110 . In this regard, the fabrication process continues forming body regions (or well regions)  144 ,  146  for the transistor structures  140 ,  142  in the active regions  108 ,  110 , forming gate structures  148 ,  150  overlying the well regions  144 ,  146 , and forming spaced-apart source and drain regions  152 ,  154  about the gate structures  148 ,  150 . The body regions  144 ,  146  may be formed by doping the active regions  108 ,  110  in a conventional manner, for example, by implanting ions of a desired conductivity-determining impurity type, to achieve a desired dopant profile for the transistor structures  140 ,  142 . As described above, the depth of the body regions  144 ,  146  relative to the upper surfaces of the semiconductor material  102  is less than the depth of the trenches (or isolation regions  104 ,  106 ), such that the body regions  144 ,  146  are electrically isolated by the isolation regions  104 ,  106 . The gate structures  148 ,  150  function as gate electrodes for the respective transistor structures  140 ,  142 , and may be fabricated using a conventional gate stack module or any combination of well-known process steps. The gate structures  148 ,  150  preferably include at least one layer of dielectric material  160 , at least one layer of conductive gate electrode material  162 , and at least one layer of a dielectric capping material  164 . In accordance with one embodiment, the gate structures  148 ,  150  are formed by depositing one or more layers of high-k dielectric material  160  overlying the semiconductor material  102 , depositing one or more layers of metal material  162  overlying the high-k dielectric material(s)  160 , and depositing one or more layers of dielectric material  164 , such as a nitride material (e.g., silicon nitride, silicon oxynitride, or the like), overlying the metal material  164 , and selectively removing portions of the high-k dielectric material  160 , metal material  162 , and capping material  164 , preferably using an anisotropic etchant, to define the gate structures  148 ,  150 . The remaining portions of the capping material  164  function as gate caps that protect the underlying metal material  162  during subsequent process steps. It should be understood that various numbers, combinations and/or arrangements of materials may be utilized for the gate structure in a practical embodiment, and the subject matter described herein is not limited to any particular number, combination, or arrangement of gate material(s) in the gate structure. 
     After the gate structures  148 ,  150  are formed, spaced-apart source and drain regions  152 ,  154  may be formed about the gate structures  148 ,  150  by implanting dopant ions of a conductivity-determining impurity type into the semiconductor material  102  to a desired depth and/or sheet resistivity using the gate structures  148 ,  150  as an implantation mask and subsequent thermal annealing. The conductivity-determining impurity type of the implanted ions used for the source/drain regions  152 ,  154  is of a conductivity type that is different from the conductivity type of the body regions  144 ,  146 , as will be appreciated in the art. It will be appreciated that although not illustrated by  FIG. 7 , in some embodiments, one or more spacers may be formed about the sidewalls of the gate structure  148 ,  150  prior to the ion implantation steps to define or otherwise control the lateral extent of the source/drain regions  152 ,  154  in a conventional manner. 
     Fabrication of the semiconductor device structure  100  may be completed using well known final process steps, such as deep ion implantation, thermal annealing, formation of conductive contacts overlying the source/drain regions and/or gate structure, formation of MOS capacitors and/or other elements on the large active region  112 , and/or other back end process steps, which will not be described in detail herein. By virtue of the hydrofluoric acid resistant caps  132 ,  134 , the isolation regions  104 ,  106  are not reduced in thickness during subsequent process steps, for example, when hydrofluoric-acid comprising etchants are subsequently used to remove or pattern oxide material or otherwise clean the surface of the semiconductor substrate. In this regard, hydrofluoric-acid comprising etchants may be used without removing or otherwise damaging the oxide material  118 ,  120  of the isolation regions  104 ,  106 . The nitride material  124  remains intact along the periphery of the active regions  108 ,  110 ,  112  thereby reducing parasitic leakage currents and/or reducing the threshold voltage (Vt) to device width (W) variations that may otherwise result from corner devices that may be created when the gate stack overlaps onto a recessed oxide isolation region. At the same time, the trenches for the isolation regions are primarily occupied by oxide material  118 ,  120  to provide or otherwise maintain reduced parasitic capacitances between active regions  108 ,  110 ,  112 . Additionally, the distance between the upper surfaces of the hydrofluoric acid resistant caps  132 ,  134  and the upper surfaces of the semiconductor material  102  of the active regions  108 ,  110 ,  112  may be made relatively small (e.g., 15 nm or less), such that the semiconductor device structure  100  has a substantially planar surface prior to forming the gate structures  148 ,  150 , which in turn, improves fine geometry photoresist processing where planar surfaces are desired. 
     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.