Patent Document

BACKGROUND 
       [0001]    The present disclosure relates to semiconductor structures, and particularly to semiconductor structures including a fin structure having a stack of a rare-earth oxide fin portion and a semiconductor fin portion, and methods of manufacturing the same. 
         [0002]    FinFETs formed on a semiconductor-on-insulator (SOI) substrate provide inherent electrical isolation among devices. However, the cost of manufacturing SOI substrates is significantly higher than the cost of manufacturing bulk substrates. While finFETs can also be formed on a bulk substrate, electrical isolation among adjacent finFETs on a bulk substrate is in general poor, and provides a leakage path among adjacent devices, thereby degrading the performance of these devices. 
       BRIEF SUMMARY 
       [0003]    A dielectric template layer is deposited on a substrate. Line trenches are formed within the dielectric template layer by an anisotropic etch that employs a patterned mask layer. The patterned mask layer can be a patterned photoresist layer, or a patterned hard mask layer that is formed by other image transfer methods. A lower portion of each line trench is filled with an epitaxial rare-earth oxide material by a selective rare-earth oxide epitaxy process. An upper portion of each line trench is filled with an epitaxial semiconductor material by a selective semiconductor epitaxy process. The dielectric template layer is recessed to form a dielectric material layer that provides lateral electrical isolation among fin structures, each of which includes a stack of a rare-earth oxide fin portion and a semiconductor fin portion. 
         [0004]    According to an aspect of the present disclosure, a semiconductor structure is provided, which includes a fin structure located on a planar top surface of a substrate, wherein the fin structure includes a rare-earth oxide fin portion and a semiconductor fin portion in contact with a top surface of the rare-earth oxide fin portion. 
         [0005]    According to another aspect of the present disclosure, a method of forming a semiconductor structure is provided. The method includes: forming a dielectric template layer on a substrate; patterning the dielectric template layer to form at least one trench therein, wherein a top surface of the substrate is physically exposed within each of the at least one trench; forming a rare-earth oxide fin portion at a lower portion of each of the at least one trench by depositing a rare-earth oxide material; and forming a semiconductor fin portion at an upper portion of each of the at least one trench by depositing a semiconductor material. 
     
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
         [0006]      FIG. 1A  is a top-down view of a first exemplary semiconductor structure after formation of a dielectric template layer and disposable mandrel structures according to a first embodiment of the present disclosure. 
           [0007]      FIG. 1B  is a vertical cross-sectional view of the first exemplary semiconductor structure of  FIG. 1A  along the vertical plane B-B′ in  FIG. 1A . 
           [0008]      FIG. 2A  is a top-down view of the first exemplary semiconductor structure after formation of a spacer structure around the disposable mandrel structures according to the first embodiment of the present disclosure. 
           [0009]      FIG. 2B  is a vertical cross-sectional view of the first exemplary semiconductor structure of  FIG. 2A  along the vertical plane B-B′ in  FIG. 2A . 
           [0010]      FIG. 3A  is a top-down view of the first exemplary semiconductor structure after removal of the disposable mandrel structures according to the first embodiment of the present disclosure. 
           [0011]      FIG. 3B  is a vertical cross-sectional view of the first exemplary semiconductor structure of  FIG. 3A  along the vertical plane B-B′ in  FIG. 3A . 
           [0012]      FIG. 4A  is a top-down view of the first exemplary semiconductor structure after application and patterning of a photoresist according to the first embodiment of the present disclosure. 
           [0013]      FIG. 4B  is a vertical cross-sectional view of the first exemplary semiconductor structure of  FIG. 4A  along the vertical plane B-B′ in  FIG. 4A . 
           [0014]      FIG. 5A  is a top-down view of the first exemplary semiconductor structure after removal of portions of the spacer structure not covered by the photoresist and removal of the photoresist according to the first embodiment of the present disclosure. 
           [0015]      FIG. 5B  is a vertical cross-sectional view of the first exemplary semiconductor structure of  FIG. 5A  along the vertical plane B-B′ in  FIG. 5A . 
           [0016]      FIG. 6A  is a top-down view of the first exemplary semiconductor structure after deposition and planarization of a masking layer according to the first embodiment of the present disclosure. 
           [0017]      FIG. 6B  is a vertical cross-sectional view of the first exemplary semiconductor structure of  FIG. 6A  along the vertical plane B-B′ in  FIG. 6A . 
           [0018]      FIG. 7A  is a top-down view of the first exemplary semiconductor structure after additional planarization of the masking layer and the spacer structures according to the first embodiment of the present disclosure. 
           [0019]      FIG. 7B  is a vertical cross-sectional view of the first exemplary semiconductor structure of  FIG. 7A  along the vertical plane B-B′ in  FIG. 7A . 
           [0020]      FIG. 8A  is a top-down view of the first exemplary semiconductor structure after removal of the spacer structures selective to the masking layer according to the first embodiment of the present disclosure. 
           [0021]      FIG. 8B  is a vertical cross-sectional view of the first exemplary semiconductor structure of  FIG. 8A  along the vertical plane B-B′ in  FIG. 8A . 
           [0022]      FIG. 9A  is a top-down view of the first exemplary semiconductor structure after transfer of a pattern in the masking layer into the dielectric template layer to form line trenches therein according to the first embodiment of the present disclosure. 
           [0023]      FIG. 9B  is a vertical cross-sectional view of the first exemplary semiconductor structure of  FIG. 9A  along the vertical plane B-B′ in  FIG. 9A . 
           [0024]      FIG. 10A  is a top-down view of the first exemplary semiconductor structure after optional removal of the masking layer according to the first embodiment of the present disclosure. 
           [0025]      FIG. 10B  is a vertical cross-sectional view of the first exemplary semiconductor structure of  FIG. 10A  along the vertical plane B-B′ in  FIG. 10A . 
           [0026]      FIG. 11A  is a top-down view of the first exemplary semiconductor structure after selective deposition of rare-earth oxide fin portions according to the first embodiment of the present disclosure. 
           [0027]      FIG. 11B  is a vertical cross-sectional view of the first exemplary semiconductor structure of  FIG. 11A  along the vertical plane B-B′ in  FIG. 11A . 
           [0028]      FIG. 12A  is a top-down view of the first exemplary semiconductor structure after selective deposition of semiconductor fin portions according to the first embodiment of the present disclosure. 
           [0029]      FIG. 12B  is a vertical cross-sectional view of the first exemplary semiconductor structure of  FIG. 12A  along the vertical plane B-B′ in  FIG. 12A . 
           [0030]      FIG. 13A  is a top-down view of the first exemplary semiconductor structure after selective recessing of the dielectric template layer to form a dielectric material layer according to the first embodiment of the present disclosure. 
           [0031]      FIG. 13B  is a vertical cross-sectional view of the first exemplary semiconductor structure of  FIG. 13A  along the vertical plane B-B′ in  FIG. 13A . 
           [0032]      FIG. 14A  is a top-down view of the first exemplary semiconductor structure after formation of a gate dielectric layer and a gate electrode according to the first embodiment of the present disclosure. 
           [0033]      FIG. 14B  is a vertical cross-sectional view of the first exemplary semiconductor structure of  FIG. 14A  along the vertical plane B-B′ in  FIG. 14A . 
           [0034]      FIG. 15A  is a top-down view of the first exemplary semiconductor structure after formation of a middle-of-line (MOL) dielectric layer and contact via structures embedded therein according to the first embodiment of the present disclosure. 
           [0035]      FIG. 15B  is a vertical cross-sectional view of the first exemplary semiconductor structure of  FIG. 15A  along the vertical plane B-B′ in  FIG. 15A . 
           [0036]      FIG. 15C  is a vertical cross-sectional view of the first exemplary semiconductor structure of  FIG. 15A  along the vertical plane C-C′ in  FIG. 15A . 
           [0037]      FIG. 16A  is a top-down view of a second exemplary semiconductor structure after application and lithographic patterning of a photoresist according to a second embodiment of the present disclosure. 
           [0038]      FIG. 16B  is a vertical cross-sectional view of the second exemplary semiconductor structure of  FIG. 16A  along the vertical plane B-B′ in  FIG. 16A . 
       
    
    
     DETAILED DESCRIPTION 
       [0039]    As stated above, the present disclosure relates to semiconductor structures including a fin structure having a stack of a rare-earth oxide fin portion and a semiconductor fin portion, and methods of manufacturing the same, which are now described in detail with accompanying figures. Like and corresponding elements mentioned herein and illustrated in the drawings are referred to by like reference numerals. The drawings are not necessarily drawn to scale. 
         [0040]    Referring to  FIGS. 1A and 1B , a first exemplary semiconductor structure according to a first embodiment of the present disclosure includes a substrate  10 , which includes a single crystalline material at least at a top surface thereof. The single crystalline material can be any single crystalline material that has the same crystalline structure as a crystalline rare-earth oxide material, i.e., a crystalline oxide of a rare-earth element. 
         [0041]    In one embodiment, the single crystalline material can be a single crystalline semiconductor material such as single crystalline silicon, a single crystalline silicon germanium alloy, a single crystalline silicon carbon alloy, a single crystalline silicon germanium carbon alloy, a single crystalline III-V compound semiconductor material, a single crystalline II-VI compound semiconductor material, or an alloy or a combination thereof. In one embodiment, the substrate  10  can include the single crystalline material in an upper portion and a different material in a lower portion. In another embodiment, the substrate  10  can include the single crystalline material throughout the entirety of the substrate  10 . In one embodiment, the substrate  10  can be a single crystalline bulk semiconductor substrate including a single crystalline semiconductor material throughout the entirety thereof. 
         [0042]    The substrate  8  can have a thickness sufficient to provide mechanical support to layers and/structure to be subsequently formed thereupon. The thickness of the substrate  8  can be from 50 microns to 2 mm, although lesser and greater thicknesses can also be employed. 
         [0043]    A dielectric template layer  20  is formed on the top surface of the substrate  10 . The dielectric template layer  20  includes a dielectric material such as silicon oxide, silicon nitride, silicon oxynitride, a dielectric metal oxide, or a combination thereof. The dielectric material of the dielectric template layer  20  can be a dielectric material other than a rare-earth oxide material. A planar bottom surface of the dielectric template layer  20  is in contact with a planar top surface of the substrate  10 . 
         [0044]    In one embodiment the dielectric template layer  20  includes a doped silicon oxide material or undoped silicon oxide material. The dielectric template layer  20  can be formed, for example, by chemical vapor deposition (CVD), atomic layer deposition (ALD), thermal and/or plasma oxidation of an underlying semiconductor material of the substrate  10  (if the substrate  10  includes a semiconductor material), thermal and/or plasma nitridation of an underlying semiconductor material of the substrate (if the substrate  10  includes a semiconductor material), or a combination thereof. 
         [0045]    In one embodiment, the dielectric template layer  20  includes silicon oxide deposited by chemical vapor deposition. The thickness of the dielectric template layer  20  can be from 50 nm to 1,000 nm, although lesser and greater thicknesses can also be employed. 
         [0046]    A disposable material different from the material of the dielectric template layer  20  is deposited and lithographically patterned to form disposable mandrel structures  42 . The disposable material can be, for example, a semiconductor material, a metallic material, or a dielectric material different from the dielectric material of the dielectric template layer. For example, the disposable material can be polysilicon, amorphous silicon, a silicon germanium alloy, a silicon carbon alloy, a III-V semiconductor material, a II-VI semiconductor material, TaN, TiN, WN, an organosilicate glass, or combinations thereof. The disposable material can be deposited as a blanket layer, i.e., a layer having a uniform thickness throughout. The thickness of the deposited disposable material can be from 50 nm to 1,000 nm, although lesser and greater thicknesses can also be employed. 
         [0047]    The layer of the deposited disposable material is patterned, for example, by applying a photoresist layer (not shown), lithographically patterning the photoresist layer, and transferring the pattern in the photoresist layer into the layer of the deposited disposable material by an etch, which can be an anisotropic etch such as a reactive ion etch. The remaining portions of the deposited disposable material constitute the disposable mandrel structures  42 . The shapes of the disposable mandrel structures  42  can be any closed shape known in the art, including, but not limited to, circles, ellipses, superellipses, regular and irregular polygons, and combinations of linear edges and curved edges that form a closed shape. 
         [0048]    In one embodiment, the shapes of the disposable mandrel structures  42  can include at least one trapezoid having a pair of parallel edges. In one embodiment, the shapes of the disposable mandrel structures  42  can include at least one parallelogram having two pairs of parallel edges. In one embodiment, the shapes of the disposable mandrel structures  42  can include at least one rectangle. In one embodiment, the shapes of the disposable mandrel structures  42  can include a plurality of rectangles. In one embodiment, the plurality of rectangles can have a width that is a critical dimension, i.e., a minimum dimension that can be printed by lithographic methods employing a single lithographic exposure and development. 
         [0049]    Referring to  FIGS. 2A and 2B , spacer structures  44  are formed around the peripheries of the disposable mandrel structures  42  by depositing a conformal material layer by a conformal deposition process, such as chemical vapor deposition (CVD), and by removing horizontal portions of the conformal material layer by an anisotropic etch. Remaining vertical portions of the conformal material layer around each disposable mandrel structure  42  constitute a spacer structure  44 . 
         [0050]    The spacer structure  44  includes a material different from the materials of the dielectric template layer  20  and the disposable mandrel structures  42 . In one embodiment, the spacer structure  44  can include a dielectric material different from the material of the dielectric template layer  20 . For example, the dielectric template layer  20  can include silicon oxide, and the spacer structure  44  can include silicon nitride. In another embodiment, the spacer structure  44  can include a semiconductor material that is different from the material of the disposable mandrel structures  42 . For example, the disposable mandrel structures  42  can include germanium or a silicon germanium alloy, and the spacer structure  44  can include silicon. In another example, the disposable mandrel structures  42  can include a metallic material, or an organosilicate glass, and the spacer structure  44  can include a semiconductor material. 
         [0051]    The bottom portion of each spacer structure  44  has a substantially uniform width between a pair of sidewall surfaces, i.e., between the inner sidewall surface and the outer sidewall surface. The width of the spacer structures  44 , as measured between an inner sidewall surface of a spacer structure  44  in contact with a vertical sidewall of a disposable mandrel structure  42  and an outer sidewall surface of the spacer structure  44 , can be from 5 nm to 200 nm, although lesser and greater widths can also be employed. In one embodiment, the width of the spacer structure  44  can be a sublithographic dimension, i.e., a dimension that is less than a critical dimension, which is the minimum dimension that can be printed by lithographic methods employing a single lithographic exposure. 
         [0052]    Referring to  FIGS. 3A and 3B , disposable mandrel structures  42  are removed selective to the spacer structures  44  and the dielectric template layer  20  by an etch, which can be a wet etch or a dry etch. A top surface of the dielectric template layer  20  is physically exposed within each cavity laterally surrounded by a spacer structure  44 . 
         [0053]    Referring to  FIGS. 4A and 4B , a photoresist  47  can be optionally applied over the spacer structures  44  and the dielectric template layer  20 , and is lithographically patterned to cover portions of the spacer structures  44 , while not covering other portions of the spacer structures  44 . 
         [0054]    In one embodiment, a spacer structure  44  can laterally enclose a rectangular cavity and have a substantially parallel pair of lengthwise portions that extend along a lengthwise direction (e.g., portions of the spacer structure  44  extending in the vertical direction in  FIG. 4A ) and a substantially parallel pair of widthwise portions that extend along a widthwise direction (e.g., portions of the spacer structure  44  extending in the horizontal direction in  FIG. 4A ). The photoresist  47  can be patterned such that the pair of widthwise portions are not covered by the photoresist  47 , while substantial portions of the pair of lengthwise portions are covered by the photoresist  47 . 
         [0055]    Referring to  FIGS. 5A and 5B , the physically exposed portions of the spacer structure  44  are removed by an etch, while portions of the spacer structure  44  covered with the photoresist  47  are not removed. The etch can be an isotropic etch or an anisotropic etch. The removal of the spacer structure  44  can be selective to the dielectric material of the dielectric template layer  20 , i.e., the etch chemistry can be selected to remove the material of the spacer structure  44 , while not removing the material of the dielectric template layer  20 . 
         [0056]    Referring to  FIGS. 6A and 6B , a masking layer  48  is deposited to fill the space above the dielectric template layer  20  that is not occupied by the spacer structures  44 . The spacer structures  44  and the masking layer  48  complimentarily fill the entirety of the space above the dielectric template layer  20 . In one embodiment, the complementary dielectric layer  48  can fill the entirety of space below the topmost surface of the spacer structures  44 . 
         [0057]    The masking layer  48  includes a material different from the material of the spacer structures  44 . The material of the masking layer  48  can be the same as, or different from, the material of the dielectric template layer  20 . The masking layer  48  is subsequently planarized to form the first exemplary structure illustrated in  FIGS. 6A and 6B . 
         [0058]    In one embodiment, the spacer structures  44  can include silicon nitride, and the masking layer  48  can include silicon oxide, a metallic material, and/or a semiconductor material. In another embodiment, the spacer structure  44  can include a semiconductor material, and the masking layer  48  can include silicon nitride, silicon oxide, and/or a metallic material. In general, the material of the spacer structures  44  and the material of the masking layer  48  can be selected such that the material of the spacer structures  44  can be removed selective to the material of the masking layer  48 . 
         [0059]    Referring to  FIGS. 7A and 7B , the spacer structures  44  and the masking layer  48  can be further planarized, for example, by chemical mechanical planarization. For example, the spacer structures  44  and the masking layer  48  can be planarized to a height at which the sidewall surfaces of the spacer structures  44  are vertical. 
         [0060]    Referring to  FIGS. 8A and 8B , the remaining portions of the spacer structures  44  are removed selective to the masking layer  48 . A line trench  49  having a pair of substantially parallel vertical sidewalls is formed within each cavity from which the remaining portions of the spacer structures  44  are removed. Each line trench  49  has a substantially uniform width between a pair of vertical sidewall surfaces of the masking layer  48 . The top surface of the dielectric template layer  20  is physically exposed at the bottom of each line trench  49 . 
         [0061]    Referring to  FIGS. 9A and 9B , the pattern in the masking layer  48  is transferred into the dielectric template layer  20  by an anisotropic etch such as a reactive ion etch. The anisotropic etch removes the dielectric material of the dielectric template layer  20  employing the masking layer  48  as a mask layer, i.e., a layer that is employed as an etch mask. A line trench  29  having a substantially uniform width between a pair of vertical sidewall surface of the dielectric template layer  20  is formed underneath each line trench (See  FIGS. 8A and 8B ) within the masking layer  48 . The sidewalls of the line trenches  29  can be vertically coincident with sidewalls of the line trenches within the masking layer  48 . In one embodiment, the width of the line trenches  29  can be a sublithographic dimension. Some or all of the masking layer  48  may be removed during the anisotropic etch that forms the line trenches  29 . 
         [0062]    Referring to  FIGS. 10A and 10B , any remaining portion of the masking layer  48  can be optionally removed. 
         [0063]    In general, at least one trench is formed within the dielectric template layer  20 . The at least one trench may, or may not, have a pair of vertical sidewalls of the patterned dielectric template layer  20 , and may, or may not, have a uniform spacing between the pair of vertical sidewalls if the pair of vertical sidewalls is present. The top surface of the substrate  10  is physically exposed within each of the at least one trench within the dielectric template layer  20 . 
         [0064]    Referring to  FIGS. 11A and 11B , a rare-earth oxide fin portion  22  is formed at a lower portion of each of the at least one trench, e.g., the line trenches  29 , by depositing a rare-earth oxide material. In one embodiment, the deposited rare-earth oxide material is a single crystalline rare-earth oxide material that is epitaxially aligned to a single crystalline material in the substrate  10 . 
         [0065]    A rare-earth oxide material is an oxide material of a rare-earth element. Rare earth elements are also referred to as Lanthanides, and include La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu. The ionic radii of rare earth elements decrease gradually with the atomic number, and the total variation of the ionic radii of rare earth elements is less than 15% among one another. The rare earth elements form various single crystalline dielectric oxides with a valance of +3, i.e., a dielectric oxide having a chemical formula of M 2 O 3 , in which M can be any of the rare earth elements. 
         [0066]    Crystalline rare earth oxides are lattice coincident on a class of elemental or alloyed single crystalline semiconductor materials including single crystalline silicon, a single crystalline silicon-germanium alloy, a single crystalline silicon-carbon alloy, and a single crystalline silicon-germanium-carbon alloy. For each single crystalline M 2 O 3  in which M is a rare earth element, at least one single crystalline semiconductor material having a lattice constant that is one half the lattice constant of the single crystalline M 2 O 3  exists among single crystalline silicon, a single crystalline silicon-germanium alloy, a single crystalline silicon-carbon alloy, and a single crystalline silicon-germanium-carbon alloy. 
         [0067]    For example, twice the lattice constant of silicon is between the lattice constant of gadolinium oxide (Gd 2 O 3 ) and the lattice constant of neodymium oxide (Nd 2 O 3 ). Thus, the composition of a single crystalline alloy of gadolinium oxide and neodymium oxide can be selected to match twice the lattice constant of silicon. In other words, the value x in the compound Gd 2-x Nd x O 3  can be selected to provide a single crystalline compound having a lattice constant that is twice the lattice constant of silicon. 
         [0068]    In another example, twice the lattice constant of germanium is between the lattice constant of praseodymium oxide (Pd 2 O 3 ) and the lattice constant of lanthanum oxide (La 2 O 3 ). Thus, the composition of a single crystalline alloy of praseodymium oxide and lanthanum oxide can be selected to match twice the lattice constant of germanium. In other words, the value y in the compound Pd 2-y La y O 3  can be selected to provide a single crystalline compound having a lattice constant that is twice the lattice constant of silicon. 
         [0069]    In a non-limiting exemplary embodiment, the rare-earth oxide fin portions  22  can include a single crystalline rare earth oxide selected from Er 2 O 3 , Gd 2 O 3 , Nd 2 O 3 , Pr 2 O 3 , La 2 O 3 , and a single crystalline alloy thereof. 
         [0070]    In addition, crystalline rare earth oxides are lattice coincident on various single crystalline semiconductor materials that include III-V compound semiconductor materials and II-VI compound semiconductor materials. Thus, for each single crystalline M 2 O 3  in which M is a rare earth element, at least one single crystalline compound semiconductor material having a lattice constant that is one half the lattice constant of the single crystalline M 2 O 3  exists. 
         [0071]    By selecting a rare-earth oxide material that is an oxide of a single rare-earth element or an oxide of an alloy of at least two rare-earth elements, the rare-earth oxide fin portions  22  can be lattice matched to the underlying single crystalline material, which can be a single crystalline semiconductor material. 
         [0072]    Method of forming a single crystalline rare-earth oxide material is described, for example, in U.S. Pat. Nos. 7,655,327 and 7,709,826 to Atanackovic. Selective deposition of a single crystalline rare-earth oxide material can be effected, for example, by modifying the deposition method of U.S. Pat. Nos. 7,655,327 and 7,709,826 to Atanackovic to provide an etchant gas, such as HCl, NF 3 , CF 4 , CHF 3 , or combinations thereof into a process chamber concurrently, or alternately, with reactant gas(es) that is/are precursors for the deposited rare-earth oxide material. During the selective deposition, the single crystalline rare-earth oxide material is deposited, and grows from, only on the single crystalline semiconductor surface of the substrate  10 , and does not nucleate, or grow from, the surfaces of the dielectric template layer  20 . 
         [0073]    In one embodiment, the substrate  10  includes a semiconductor material such as single crystalline silicon, a single crystalline silicon-germanium alloy, a single crystalline silicon-carbon alloy, or a single crystalline slicon-germanium-carbon alloy, and the rare-earth oxide fin portions  22  include a single crystalline rare earth oxide material selected from single crystalline Er 2 O 3 , single crystalline Gd 2 O 3 , single crystalline Nd 2 O 3 , single crystalline Pr 2 O 3 , single crystalline La 2 O 3 , and a single crystalline alloy thereof. 
         [0074]    Referring to  FIGS. 12A and 12B , a semiconductor fin portion  30  is formed at an upper portion of each of the at least one trench, e.g., the line trenches  29  (See  FIG. 11B ), by depositing a semiconductor material. 
         [0075]    In one embodiment, the rare-earth oxide fin portions  22  can include a single crystalline rare-earth oxide material, and the semiconductor fin portions  30  can include a single crystalline semiconductor material that is epitaxially aligned to the single crystalline rare-earth oxide material of the rare-earth oxide fin portions  22 . 
         [0076]    The height of the top surface of the semiconductor fin portions  30  can be coplanar with, located above, or recessed below, the top surface of the dielectric template layer  20 . If the top surfaces of the semiconductor fin portions  30  are raised above the top surface of the dielectric template layer  20 , a planarization process can be performed to make the top surfaces of the semiconductor fin portions  30  coplanar with the top surface of the dielectric template layer  20 . 
         [0077]    Each stack, from bottom to top, of a rare-earth oxide fin portion  22  and an overlying semiconductor fin portion  30  can be a fin structure ( 22 ,  30 ). As used herein, a fin structure is a structure having a pair of lengthwise sidewalls that is longer than the distance between the pair of lengthwise sidewalls, i.e., the width of the fin structure. The semiconductor fin portion  30  is in contact with a top surface of the rare-earth oxide fin portion  22 . The fin structure ( 22 ,  30 ) is located on a planar top surface of the substrate  10 . 
         [0078]    Referring to  FIGS. 13A and 13B , the dielectric template layer  20  is recessed selective to the fin structures ( 22 ,  30 ), i.e., recessed without etching the fin structure ( 22 ,  30 ). The remaining portion of the dielectric template layer  20  after the recessing constitutes a dielectric material layer  20 ′. The dielectric material layer  20 ′ has a planar top surface that is recessed relative to a top surface of the semiconductor fin portions  30 , and a planar bottom surface that is in contact with the top surface of the substrate  10 . 
         [0079]    In one embodiment, the top surface of the dielectric material layer  20 ′ can be located below the level of an interface between a rare-earth oxide fin portion  22  and a semiconductor fin portion  30 . 
         [0080]    Referring to  FIGS. 14A and 14B , a gate dielectric layer  50  can be formed, for example, by conformally depositing a dielectric material such as a dielectric metal oxide, silicon oxide, silicon nitride, or a combination thereof. The gate dielectric layer  50  contacts sidewalls of the semiconductor fin portions  30 . In one embodiment, the gate dielectric layer  50  can contact all top surfaces and sidewall surfaces of the semiconductor fin portions  30 , upper portions of the sidewall surfaces of the rare-earth oxide fin portions  22 , and the top surface of the dielectric material layer  20 ′. 
         [0081]    A gate electrode  52  is formed over a middle portion of at least one fin structure ( 22 ,  30 ), for example, by depositing a conductive material layer and patterning the conductive material layer. The gate electrode  52  can overlie one or multiple fin structures ( 22 ,  30 ). In one embodiment, the gate electrode  52  can be spaced from a top surface and sidewall surfaces of each semiconductor fin portion  30  by the gate dielectric layer  50 . 
         [0082]    Source and drain ion implantation can be performed to convert end portions of each semiconductor fin portion  30  into a source region  34  and a drain region  36 . The remaining unimplanted region of each semiconductor fin portion  30  is a body region  35 , which underlies the gate electrode  50 . The source region  34  is located at one end of a semiconductor fin portion  30 . The drain region  36  is located at another end of the semiconductor fin portion  30 . Gate spacers (not shown) can be optionally formed prior to, or after, the ion implantation process(es) that form(s) the source and drain regions ( 34 ,  36 ). 
         [0083]    Referring to  FIGS. 15A ,  15 B, and  15 C, a middle-of-line (MOL) dielectric layer  80  can be deposited over the gate electrode  52  and the gate dielectric layer  50 , and subsequently planarized to provide a planar top surface. The MOL dielectric layer  80  includes one or more dielectric materials such as silicon oxide, silicon nitride, a dielectric metal oxide, and a porous or non-porous organosilicate glass (OSG). 
         [0084]    Various contact via structures can be formed within the MOL dielectric layer  80 , for example, by forming contact via holes and filling the contact via holes with a conductive material. Excess conductive material above the top surface of the MOL dielectric layer  85  can be removed, for example, by chemical mechanical planarization. The various contact via structures can include, for example, source-side contact via structures  84 , gate-side contact via structures  85 , and drain-side contact via structures  86 . 
         [0085]    Referring to  FIGS. 16A and 16B , a second exemplary semiconductor structure according to a second embodiment of the present disclosure can be derived from the first exemplary semiconductor structure of  FIGS. 1A and 1B  by applying a photoresist layer  27  and lithographically patterning the photoresist layer  27  to include various trenches  19  therein. In one embodiment, at least one of the various trenches  19  can be a line trench having a pair of parallel vertical sidewalls. 
         [0086]    The pattern in the photoresist layer  27  can be transferred into the dielectric template layer  20 , for example, by an anisotropic etch, to form trenches, which can be line trenches, in the dielectric template layer  20 . The top surface of the substrate  20  is physically exposed at a bottom of each trench within the dielectric template layer  20  so that a structure illustrated in  FIGS. 10A and 10B  can be formed. The widths of the trenches in the dielectric template layer  20  according to the second embodiment are lithographic dimensions, i.e., equal to, or greater than, a critical dimension, i.e., a minimum dimension that can be printed with lithographic methods employing single lithographic exposure. 
         [0087]    The processing steps if  FIGS. 12A ,  12 B,  13 A,  13 B,  14 A,  14 B,  15 A,  15 B, and  15 C can be subsequently performed in the second embodiment to form a structure illustrated in  FIGS. 15A ,  15 B, and  15 C. 
         [0088]    While the disclosure has been described in terms of specific embodiments, it is evident in view of the foregoing description that numerous alternatives, modifications and variations will be apparent to those skilled in the art. Various embodiments of the present disclosure can be employed either alone or in combination with any other embodiment, unless expressly stated otherwise or otherwise clearly incompatible among one another. Accordingly, the disclosure is intended to encompass all such alternatives, modifications and variations which fall within the scope and spirit of the disclosure and the following claims.

Technology Category: 5