Patent Publication Number: US-11049945-B2

Title: Semiconductor device structure and method for forming the same

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application is a Divisional of pending U.S. patent application Ser. No. 15/494,023, filed Apr. 21, 2017 and entitled “Semiconductor device structure and method for forming the same”, which claims the benefit of U.S. Provisional Application No. 62/427,063, filed on Nov. 28, 2016, and entitled “Semiconductor device structure and method for forming the same”, the entirety of which is incorporated by reference herein. 
    
    
     BACKGROUND 
     The semiconductor integrated circuit (IC) industry has experienced rapid growth. Technological advances in IC materials and design have produced generations of ICs. Each generation has smaller and more complex circuits than the previous generation. 
     In the course of IC evolution, functional density (i.e., the number of interconnected devices per chip area) has generally increased while geometric size (i.e., the smallest component (or line) that can be created using a fabrication process) has decreased. This scaling-down process generally provides benefits by increasing production efficiency and lowering associated costs. 
     However, these advances have increased the complexity of processing and manufacturing ICs. Since feature sizes continue to decrease, fabrication processes continue to become more difficult to perform. Therefore, it is a challenge to form reliable semiconductor device structures at smaller and smaller sizes. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Aspects of the present disclosure are best understood from the following detailed description when read with the accompanying figures. It should be noted that, in accordance with the standard practice in the industry, various features are not drawn to scale. In fact, the dimensions of the various features may be arbitrarily increased or reduced for clarity of discussion. 
         FIGS. 1A-1F  are cross-sectional views of various stages of a process for forming a semiconductor device structure, in accordance with some embodiments. 
         FIGS. 2A-2E  are cross-sectional views of various stages of a process for forming a semiconductor device structure, in accordance with some embodiments. 
         FIGS. 3A-3F  are cross-sectional views of various stages of a process for forming a semiconductor device structure, in accordance with some embodiments. 
         FIGS. 4A and 4B  are cross-sectional views of various stages of a process for forming a semiconductor device structure, in accordance with some embodiments. 
         FIGS. 5A-5D  are cross-sectional views of various stages of a process for forming a semiconductor device structure, in accordance with some embodiments. 
     
    
    
     DETAILED DESCRIPTION 
     The following disclosure provides many different embodiments, or examples, for implementing different features of the subject matter provided. Specific examples of components and arrangements are described below to simplify the present disclosure. These are, of course, merely examples and are not intended to be limiting. For example, the formation of a first feature over or on a second feature in the description that follows may include embodiments in which the first and second features are formed in direct contact, and may also include embodiments in which additional features may be formed between the first and second features, such that the first and second features may not be in direct contact. In addition, the present disclosure may repeat reference numerals and/or letters in the various examples. This repetition is for the purpose of simplicity and clarity and does not in itself dictate a relationship between the various embodiments and/or configurations discussed. 
     Furthermore, spatially relative terms, such as “beneath,” “below,” “lower,” “above,” “upper” and the like, may be used herein for ease of description to describe one element or feature&#39;s relationship to another element(s) or feature(s) as illustrated in the figures. The spatially relative terms are intended to encompass different orientations of the device in use or operation in addition to the orientation depicted in the figures. The apparatus may be otherwise oriented (rotated 90 degrees or at other orientations) and the spatially relative descriptors used herein may likewise be interpreted accordingly. 
     The fins may be patterned by any suitable method. For example, the fins may be patterned using one or more photolithography processes, including double-patterning or multi-patterning processes. Generally, double-patterning or multi-patterning processes combine photolithography and self-aligned processes, allowing patterns to be created that have, for example, pitches smaller than what is otherwise obtainable using a single, direct photolithography process. For example, in one embodiment, a sacrificial layer is formed over a substrate and patterned using a photolithography process. Spacers are formed alongside the patterned sacrificial layer using a self-aligned process. The sacrificial layer is then removed, and the remaining spacers may then be used to pattern the fins. 
     Some embodiments of the disclosure are described.  FIGS. 1A-1F  are cross-sectional views of various stages of a process for forming a semiconductor device structure, in accordance with some embodiments. Additional operations can be provided before, during, and/or after the stages described in  FIGS. 1A-1F . Some of the stages that are described can be replaced or eliminated for different embodiments. Additional features can be added to the semiconductor device structure. Some of the features described below can be replaced or eliminated for different embodiments. 
     As shown in  FIG. 1A , a semiconductor substrate  102  is provided. In some embodiments, the semiconductor substrate  102  is a bulk semiconductor substrate, such as a semiconductor wafer. For example, the semiconductor substrate  102  is a silicon wafer. The semiconductor substrate  102  may include silicon or another elementary semiconductor material such as germanium. In some other embodiments, the semiconductor substrate  102  includes a compound semiconductor. The compound semiconductor may include gallium arsenide, silicon carbide, indium arsenide, indium phosphide, another suitable compound semiconductor, or a combination thereof. 
     In some embodiments, the semiconductor substrate  102  includes a semiconductor-on-insulator (SOI) semiconductor substrate. The SOI semiconductor substrate may be fabricated using a separation by implantation of oxygen (SIMOX) process, a wafer bonding process, another applicable method, or a combination thereof. 
     In some embodiments, the semiconductor substrate  102  includes various doping regions (not shown) according to design requirements of semiconductor elements. For example, the doping regions include p-type wells and/or n-type wells. In some embodiments, the doping regions are doped with p-type dopants. For example, the doping regions are doped with boron (B) or boron difluoride (BF 2 ). In some embodiments, the doping regions are doped with n-type dopants. For example, the doping regions are doped with phosphorus (P) or arsenic (As). In some embodiments, some doping regions are p-type doped regions and other doping regions are n-type doped regions. 
     In accordance with some embodiments, one or more fin structures (not shown) are formed over the semiconductor substrate  102 . In some embodiments, multiple recesses (or trenches) are formed in the semiconductor substrate  102 . As a result, multiple fin structures are formed between the recesses. In some embodiments, one or more photolithography and etching processes are used to partially remove the semiconductor substrate  102  and form the recesses. 
     As shown in  FIG. 1A , spacer elements  104 A,  104 B,  104 C and  104 D are formed over the semiconductor substrate  102 , in accordance with some embodiments. In some embodiments, the spacer elements  104 A,  104 B,  104 C and  104 D are formed over the fin structures of the semiconductor substrate  102 . 
     In accordance with some embodiments, the spacer elements  104 A,  104 B,  104 C and  104 D are used to assist in the formation of source and drain structures in subsequent processes. In some embodiments, the spacer elements  104 A,  104 B,  104 C and  104 D are made of silicon nitride, silicon oxynitride, silicon carbide, another suitable material, or a combination thereof. In some embodiments, the spacer elements  104 A,  104 B,  104 C and  104 D are formed using a deposition process, such as a chemical vapor deposition (CVD) process, and an etching process. 
     As shown in  FIG. 1A , gate structures  106 A and  106 B are formed over the semiconductor substrate  102 , in accordance with some embodiments. In some embodiments, the gate structures  106 A and  106 B are formed over the fin structures of the semiconductor substrate  102 . 
     As shown in  FIG. 1A , two adjacent spacer elements  104 A and  104 B and the semiconductor substrate  102  together surround an opening  108 A, in accordance with some embodiments. The gate structure  106 A is formed in the opening  108 A between the two adjacent spacer elements  104 A and  104 B. In other words, the spacer elements  104 A and  104 B are at opposite sides of the gate structure  106 A, in accordance with some embodiments. 
     As shown in  FIG. 1A , two adjacent spacer elements  104 C and  104 D and the semiconductor substrate  102  together surround an opening  108 B, in accordance with some embodiments. The gate structure  106 B is formed in the opening  108 B between the two adjacent spacer elements  104 C and  104 D. In other words, the spacer elements  104 C and  104 D are at opposite sides of the gate structure  106 B, in accordance with some embodiments. 
     Furthermore, as shown in  FIG. 1A , the top surfaces of the spacer elements  104 A,  104 B,  104 C and  104 D are higher than the top surface of the gate structures  106 A and  106 B, in accordance with some embodiments. In some embodiments, the spacer elements  104 A and  104 B and the gate structure  106 A together surround a recess  110 A. In some embodiments, the spacer elements  104 C and  104 D and the gate structure  106 B together surround a recess  110 B. 
     As shown in  FIG. 1A , the gate structure  106 A includes a gate dielectric layer  112 A, work function layers  114 A and  116 A, and a gate electrode layer  118 A, in accordance with some embodiments. The gate dielectric layer  112 A, the work function layer  114 A, the work function layer  116 A and the gate electrode layer  118 A are sequentially positioned over the semiconductor substrate  102 . 
     In some embodiments, the gate structure  106 B includes a gate dielectric layer  112 B, work function layers  114 B,  116 B and  120 B, and a gate electrode layer  118 B. The gate dielectric layer  112 B, the work function layer  114 B, the work function layer  120 B, the work function layer  116 B and the gate electrode layer  118 B are sequentially positioned over the semiconductor substrate  102 . 
     As shown in  FIG. 1A , the gate dielectric layers  112 A and  112 B are substantially conformally deposited in the openings  108 A and  108 B, respectively, in accordance with some embodiments. In some embodiments, the gate dielectric layer  112 A is over the semiconductor substrate  102  and partially covers the sidewalls of the spacer elements  104 A and  104 B. In some embodiments, the gate dielectric layer  112 B is over the semiconductor substrate  102  and partially covers the sidewalls of the spacer elements  104 C and  104 D. 
     As shown in  FIG. 1A , the work function layers  114 A and  114 B are substantially conformally deposited over the gate dielectric layers  112 A and  112 B, respectively, in accordance with some embodiments. In some embodiments, the work function layer  116 A and the gate electrode layer  118 A are sequentially deposited over the work function layer  114 A. In some embodiments, the work function layer  116 A and the gate electrode layer  118 A are substantially conformally deposited. 
     In some embodiments, the work function layer  120 B, the work function layer  116 B and the gate electrode layer  118 B are sequentially deposited over the work function layer  114 B. In some embodiments, the work function layer  120 B, the work function layer  116 B and the gate electrode layer  118 B are substantially conformally deposited. 
     In some embodiments, the gate dielectric layers  112 A and  112 B are made of silicon oxide, silicon nitride, silicon oxynitride, dielectric material with a high dielectric constant (high-K), another suitable dielectric material, or a combination thereof. Examples of high-K dielectric materials include hafnium oxide (HfO 2 ), zirconium oxide, aluminum oxide, hafnium dioxide-alumina alloy, hafnium silicon oxide, hafnium silicon oxynitride, hafnium tantalum oxide, titanium oxide, hafnium titanium oxide, hafnium zirconium oxide, another suitable high-K material, or a combination thereof. High-K dielectric materials may also include metal oxide, metal nitride, metal silicates, transition metal-oxide, transition metal-nitride, transition metal-silicates, metal oxynitride, metal aluminates, zirconium silicates, zirconium aluminates, HfO 2 —Al 2 O 3  alloy, another suitable material, or a combination thereof. In some embodiments, the gate dielectric layers  112 A and  112 B have substantially the same material. 
     In some embodiments, the work function layers  114 A,  114 B,  116 A,  116 B and  120 B are used to provide the desired work function for transistors to enhance device performance including improved threshold voltage. In the embodiments of forming an NMOS transistor, the work function layers  114 A,  114 B,  116 A,  116 B and/or  120 B can be an N-type metal layer. The N-type metal layer is capable of providing a work function value suitable for the device. The work function value may be substantially equal to or less than about 4.5 eV. The N-type metal layer may include metal, metal carbide, metal nitride, or a combination thereof. For example, the N-type metal layer includes tantalum, tantalum nitride, another suitable material, or a combination thereof. 
     On the other hand, in the embodiments of forming a PMOS transistor, the work function layers  114 A,  114 B,  116 A,  116 B and/or  120 B can be a P-type metal layer. The P-type metal layer is capable of providing a work function value suitable for the device. The work function value may be substantially equal to or greater than about 4.8 eV. The P-type metal layer may include metal, metal carbide, metal nitride, other suitable materials, or a combination thereof. For example, the P-type metal includes titanium, titanium nitride, other suitable materials, or a combination thereof. 
     Many variations and/or modifications can be made to embodiments of the disclosure. In some other embodiments, the work function layers  114 A,  114 B,  116 A,  116 B and/or  120 B includes hafnium, zirconium, titanium, tantalum, aluminum, a metal carbide (e.g., hafnium carbide, zirconium carbide, titanium carbide, aluminum carbide), aluminides, ruthenium, palladium, platinum, cobalt, nickel, and conductive metal oxides, or a combination thereof. The thickness and/or the components of the work function layers  114 A,  114 B,  116 A,  116 B and  120 B may be adjusted to fine-tune the work function level thereof. 
     In some embodiments, the work function layers  114 A and  116 A of the gate structure  106 A are made of different materials. In some embodiments, the work function layers  114 B,  116 B and  120 B of the gate structure  106 B are made of different materials. 
     In some embodiments, the work function layer  114 A of the gate structure  106 A and the work function layer  114 B of the gate structure  106 B are made of substantially the same material. In some embodiments, the work function layer  116 A of the gate structure  106 A and the work function layer  116 B of the gate structure  106 B are made of substantially the same material. 
     In some embodiments, the gate electrode layer  118 A provides an electrical connection between the work function layer  116 A and a subsequently formed contact that is coupled to the gate electrode layer  118 A. In some embodiments, the gate electrode layer  118 B provides an electrical connection between the work function layer  116 B and a subsequently formed contact that is coupled to the gate electrode layer  118 B. In some embodiments, the gate electrode layers  118 A and  118 B are made of a suitable metal material. The metal material may include aluminum, tungsten, copper, gold, platinum, cobalt, another suitable metal material, an alloy thereof, or a combination thereof. 
     In some embodiments, the gate structures  106 A and  106 B are formed by a gate replacement process. The gate replacement process may be performed after the formation of an etch stop layer  124  and a dielectric layer  126 , which will be described in more detail later. In some embodiments, a dummy or sacrificial gate (not shown) between the spacer elements  104 A and  104 B are removed to form the opening  108 A. In some embodiments, a dummy or sacrificial gate (not shown) between the spacer elements  104 C and  104 D are removed to form the opening  108 B. In some embodiments, the dummy gate is made of a sacrificial material, for example, polysilicon. 
     In some embodiments, a gate dielectric material layer for forming the gate dielectric layers  112 A and  112 B is deposited over the spacer elements  104 A,  104 B,  104 C and  104 D. The gate dielectric material layer may be deposited in the openings  108 A and  108 B substantially conformally. In some embodiments, the gate dielectric material layer is deposited using an atomic layer deposition (ALD) process, a CVD process, a spin-on process, another applicable process, or a combination thereof. In some embodiments, a high-temperature annealing operation is performed to reduce or eliminate defects in the gate dielectric layers  112 A and  112 B. 
     Afterwards, a first work function material layer for forming the work function layers  114 A and  114 B is deposited over the gate dielectric material layer, in accordance with some embodiments. The first work function material layer may be deposited over the gate dielectric material layer in the openings  108 A and  108 B substantially conformally. 
     Subsequently, a patterned mask layer (not shown) is formed to cover and/or fill the opening  108 A. It is ensured that a subsequently formed second work function material layer is deposited in the opening  108 B without being deposited in the opening  108 A. The mask layer is also referred to as a blocking layer. In some embodiments, the mask layer includes polysilicon, amorphous silicon, silicon nitride, silicon oxide, silicon oxynitride, silicon carbide, spin-on glass (SOG), another suitable material, or a combination thereof. 
     In some embodiments, a hard mask material for forming the mask layer is deposited. The hard mask material fills up the openings  108 A and  108 B and extends outside the openings  108 A and  108 B. Afterwards, a planarization process is performed to remove the hard mask material outside the openings  108 A and  108 B. The planarization process may include a chemical mechanical polishing (CMP) process, a grinding process, an etching process, another applicable process, or a combination thereof. 
     In some embodiments, a patterned mask element (not shown) is formed to cover the hard mask material remaining in the opening  108 A. As a result, the hard mask material remaining in the opening  108 B is exposed. In some embodiments, the patterned mask element is a patterned photoresist layer. Subsequently, the hard mask material remaining in the opening  108 B is removed using a suitable etchant, in accordance with some embodiments. The patterned mask element is then removed. As a result, the hard mask material remaining in the opening  108 A form the patterned mask layer covering and/or filling the opening  108 A. 
     Afterwards, a second work function material layer for forming the work function layer  120 B is substantially conformally deposited over the first work function material layer in the opening  108 B, in accordance with some embodiments. Due to the patterned mask layer covering and/or filling the opening  108 A, the second work function material layer is not deposited in the opening  108 A. The patterned mask layer is then removed. 
     Afterwards, a third work function material layer for forming the work function layers  116 A and  116 B is deposited, in accordance with some embodiments. In some embodiments, the third work function material layer is substantially conformally deposited over the first work function material layer in the opening  108 A and the second work function material layer in the opening  108 B. Subsequently, a gate electrode material layer is substantially conformally deposited to fill up the openings  108 A and  108 B. 
     In some embodiments, the first, second and third work function material layers and the gate electrode material layer are deposited using suitable deposition processes. The deposition processes may include an ALD process, a physical vapor deposition (PVD) process, an electroplating process, an electroless plating process, a CVD process, another applicable process, or a combination thereof. 
     In some embodiments, a planarization process is performed to remove the gate dielectric material layer, the first, second and third work function material layers and the gate electrode material layer outside the openings  108 A and  108 B. The planarization process may include a CMP process, a grinding process, an etching process, another applicable process, or a combination thereof. 
     Afterwards, the gate dielectric material layer, the first and second work function material layers and the gate electrode material layer in the opening  108 A are partially removed, in accordance with some embodiments. As a result, the gate structure  106 A and the recess  110 A are formed in the opening  108 A. In some embodiments, the gate dielectric material layer, the first, second and third work function material layers and the gate electrode material layer in the opening  108 B are partially removed. As a result, the gate structure  106 B and the recess  110 B are formed in the opening  108 B. 
     In some embodiments, the gate dielectric material layer, the first and second work function material layers and the gate electrode material layer in the openings  108 A and  108 B are partially removed using etching processes or other applicable processes. 
     In accordance with some embodiments, the gate dielectric material layer remaining in the opening  108 A forms the gate dielectric layer  112 A. The first and second work function material layers remaining in the opening  108 A respectively form the work function layers  114 A and  116 A. The gate electrode material layer remaining in the opening  108 A forms the gate electrode layer  118 A. 
     In accordance with some embodiments, the gate dielectric material layer remaining in the opening  108 B forms the gate dielectric layer  112 B. The first, second and third work function material layers remaining in the opening  108 B respectively form the work function layers  114 B,  120 B and  116 B. The gate electrode material layer remaining in the opening  108 B forms the gate electrode layer  118 B. 
     It should be noted that the formation method of the gate structures  106 A and  106 B is not limited. The gate structures  106 A and  106 B may be formed by another applicable fabrication process. 
     As shown in  FIG. 1A , a source or drain structure  122  is over the semiconductor substrate  102  between the gate structures  106 A and  106 B, in accordance with some embodiments. In some embodiments, the source or drain structure  122  is over the semiconductor substrate  102  between the spacer elements  104 B and  104 C. 
     In some embodiments, the source or drain structure  122  is used as a strained structure. The source or drain structure  122  provides the channel region under the gate structures  106 A and  106 B with strain or stress. Therefore, the carrier mobility of the device is increased and device performance is enhanced. 
     In some embodiments, the source or drain structure  122  includes an N-type semiconductor material. In some embodiments, the source or drain structure  122  includes an epitaxially grown material, such as silicon, silicon phosphide (SiP), and/or another suitable semiconductor material. 
     Embodiments of the disclosure have many variations. In some embodiments, the source or drain structure  122  includes a P-type semiconductor material. In some embodiments, the source or drain structure  122  includes an epitaxially grown material, such as silicon germanium (SiGe) and/or another suitable semiconductor material. 
     In some embodiments, the semiconductor substrate  102  between the spacer elements  104 B and  104 C is etched to form a recess. Afterwards, a semiconductor material is epitaxially grown in the recess and is growing continually to form the source or drain structure  122 . 
     In some embodiments, the source or drain structure  122  is formed using a selective epitaxy growth (SEG) process, a CVD process (e.g., a vapor-phase epitaxy (VPE) process, a low pressure CVD (LPCVD) process, and/or an ultra-high vacuum CVD (UHV-CVD) process), a molecular beam epitaxy process, deposition of doped amorphous semiconductor (e.g. Si, Ge or SiGe) followed by a solid-phase epitaxial recrystallization (SPER) step, another applicable process, or a combination thereof. The formation process of the source or drain structure  122  may use gaseous and/or liquid precursors that can react with components of the semiconductor substrate  102  below the source or drain structure  122 . 
     In some embodiments, the source or drain structure  122  is doped with one or more suitable dopants. For example, the source or drain structure  122  is a Si source or drain feature doped with phosphorus (P), arsenic (As), antimony (Sb), or another suitable dopant. Alternatively, the source or drain structure  122  is a SiGe source or drain feature doped with boron (B) or another suitable dopant. 
     In some embodiments, the source or drain structure  122  is doped in-situ during the growth of the source or drain structure  122 . In some other embodiments, the source or drain structure  122  is not doped during the growth of the source or drain structure  122 . After the epitaxial growth, the source or drain structure  122  is doped in a subsequent process. In some embodiments, the doping is achieved using an ion implantation process, a plasma immersion ion implantation process, a gas and/or solid source diffusion process, another applicable process, or a combination thereof. In some embodiments, the source or drain structure  122  is further exposed to annealing processes to activate the dopants. For example, a rapid thermal annealing process is performed. 
     As shown in  FIG. 1A , the etch stop layer  124  is formed over the sidewalls of the spacer elements  104 A,  104 B,  104 C and  104 D, the semiconductor substrate  102  and the source or drain structure  122 , in accordance with some embodiments. In some embodiments, the etch stop layer  124  includes silicon nitride, silicon oxynitride, silicon oxycarbide, silicon carbide, another suitable material, or a combination thereof. 
     As shown in  FIG. 1A , the dielectric layer  126  is formed over the etch stop layer  124 , in accordance with some embodiments. In some embodiments, the dielectric layer  126  includes silicon oxide, silicon nitride, silicon oxynitride, another suitable material, or a combination thereof. 
     In some embodiments, an etch stop material layer and a dielectric material layer are sequentially deposited over the semiconductor substrate  102 , the spacer elements  104 A,  104 B,  104 C and  104 D, and the source or drain structure  122 . In some embodiments, the etch stop material layer and the dielectric material layer are deposited using a CVD process, a spin-on process, another applicable process, or a combination thereof. 
     In some embodiments, a planarization process is subsequently performed to partially remove the etch stop material layer and the dielectric material layer. In some embodiments, the etch stop material layer and the dielectric material layer are partially removed until the spacer elements  104 A,  104 B,  104 C and  104 D are exposed. As a result, the remaining portion of the etch stop material layer forms the etch stop layer  124 . The remaining portion of the dielectric material layer forms the dielectric layer  126 . The planarization process may include a CMP process, a grinding process, an etching process, another applicable process, or a combination thereof. However, embodiments of the disclosure are not limited thereto. In some other embodiments, the etch stop layer  124  is not formed. 
     As mentioned above, in some embodiments, the gate replacement process is performed after the formation of the etch stop layer  124  and the dielectric layer  126 . As a result, the gate structures  106 A and  106 B are formed. 
     As shown in  FIG. 1B , protection layers  128 A and  128 B are formed in the recesses  110 A and  110 B, respectively, in accordance with some embodiments. In some embodiments, the protection layer  128 A is over the gate structure  106 A and covers the work function layers  114 A and  116 A and the gate electrode layer  118 A. In some embodiments, the protection layer  128 B is over the gate structure  106 B and covers the work function layers  114 B,  116 B and  120 B and the gate electrode layer  118 B. In some embodiments, the protection layers  128 A and  128 B are also referred to as a protection material layer. 
     In accordance with some embodiments, the formation of the protection layers  128 A and  128 B includes a non-plasma process or a substantial plasma-free process. In some embodiments, the protection layers  128 A and  128 B, which are formed using a non-plasma process, cover the work function layers and the gate electrode layer of the gate structures  106 A and  106 B. The work function layers and the gate electrode layer of the gate structures  106 A and  106 B are prevented from being in direct contact with plasma during subsequent processes. The subsequent processes may include one or more plasma-involved processes. As a result, current leakage via the gate structures  106 A and  106 B, which may be the result of plasma-induced damage to the gate structures  106 A and  106 B, is reduced or eliminated. Accordingly, the breakdown voltage of the semiconductor device structure is improved in some embodiments. Therefore, the reliability and stability of the semiconductor device structure is significantly enhanced. 
     In some embodiments, the protection layers  128 A and  128 B include a metal oxide material. In some embodiments, each of the protection layers  128 A and  128 B includes aluminum oxide, tungsten oxide, copper oxide, gold oxide, platinum oxide, cobalt oxide, titanium oxide, tantalum oxide, hafnium oxide, zirconium oxide, ruthenium oxide, palladium oxide, nickel oxide, another suitable metal oxide material, or a combination thereof. 
     In some embodiments, the protection layers  128 A and  128 B are made of substantially the same material. However, embodiments of the disclosure are not limited thereto. In some other embodiments, the protection layers  128 A and  128 B are made of different materials. 
     In accordance with some embodiments, the protection layers  128 A and  128 B are formed by oxidizing the surface portion or top portion of the gate structures  106 A and  106 B, respectively. In some embodiments, the structure shown in  FIG. 1A  is transferred in a reaction chamber. A reactant is fed in the reaction chamber and the structure shown in  FIG. 1A  is heated. As a result, the surface portion of the gate structures  106 A and  106 B is oxidized. In some embodiments, the reactant is an oxygen-containing gas, such as oxygen gas (O 2 ), another suitable reactant, or a combination thereof. 
     In some embodiments, the oxidation of the surface portion of the gate structures  106 A and  106 B is performed at a temperature that is in a range from about 300 degrees C. to about 700 degrees C. In some embodiments, the temperature is in a range from about 400 degrees C. to about 600 degrees C. In some cases, the temperature should be substantially equal to or greater than about 300 degrees C. If the temperature is less than about 300 degrees C., the surface portion of the gate structures  106 A and  106 B is insufficiently oxidized. As a result, the protection layers  128 A and  128 B are not formed or they have a deficient thickness. The protection of the gate structures  106 A and  106 B from plasma may be insufficient. However, embodiments of the disclosure are not limited thereto. In some other cases, the temperature may be less than about 300 degrees C. 
     In some cases, the temperature should be substantially equal to or less than about 700 degrees C. If the temperature is greater than about 700 degrees C., the device may be negatively affected. However, embodiments of the disclosure are not limited thereto. In some other cases, the temperature may be greater than about 700 degrees C. 
     As shown in  FIG. 1B , the surface portion or top portion of the work function layers  114 A and  116 A and the gate electrode layer  118 A are oxidized, in accordance with some embodiments. As a result, the protection layer  128 A is formed. In some embodiments, the surface portion or top portion of the work function layers  114 B,  116 B and  120 B and the gate electrode layer  118 B are oxidized. As a result, the protection layer  128 B is formed. 
     As shown in  FIG. 1B , the protection layer  128 A does not directly adjoin the sidewalls of the spacer elements  104 A and  104 B, in accordance with some embodiments. In some embodiments, the protection layer  128 B does not directly adjoin the sidewalls of the spacer elements  104 C and  104 D. 
     In accordance with some embodiments, the protection layers  128 A and  128 B have a thickness that is in a range from about 5 angstrom (A) to about 30 Å. In some embodiments, the thickness of the protection layers  128 A and  128 B is in a range from about 10 Å to about 20 Å. In some cases, the thickness of the protection layers  128 A and  128 B should be substantially equal to or greater than about 5 Å. If the thickness of the protection layers  128 A and  128 B is less than about 5 Å, the protection layers  128 A and  128 B may not provide the gate structures  106 A and  106 B with enough protection from plasma. However, embodiments of the disclosure are not limited thereto. In some other cases, the thickness of the protection layers  128 A and  128 B may be less than about 5 Å. 
     In some cases, the thickness of the protection layers  128 A and  128 B should be substantially equal to or less than about 30 Å. If the thickness of the protection layers  128 A and  128 B is greater than about 30 Å, the fabrication cost of the formation of the protection layers  128 A and  128 B is undesirably increased. However, embodiments of the disclosure are not limited thereto. In some other cases, the thickness of the protection layers  128 A and  128 B may be greater than about 30 Å. 
     As shown in  FIG. 1C , a protection material layer  130  is deposited, in accordance with some embodiments. The protection material layer  130  is over the protection layers  128 A and  128 B, the spacer elements  104 A,  104 B,  104 C and  104 D, the etch stop layer  124  and the dielectric layer  126 . In some embodiments, the protection material layer  130  fills up the recesses  110 A and  110 B, as shown in  FIG. 1C . 
     In some embodiments, the protection material layer  130  includes a dielectric material. In some embodiments, the dielectric material includes silicon oxide, silicon oxycarbide, silicon nitride, nitrogen silicon carbide, another suitable material, or a combination thereof. In some embodiments, the protection material layer  130  is deposited using a plasma-involved deposition process, another applicable process, or a combination thereof. For example, the plasma-involved deposition process may be a plasma-enhanced CVD (PECVD) process or another applicable process. The deposition of the protection material layer  130  may be a self-alignment contact (SAC) process. 
     As shown in  FIG. 1D , the protection material layer  130  outside the recesses  110 A and  110 B is removed, in accordance with some embodiments. In some embodiments, the protection material layer  130  is partially removed until the spacer elements  104 A,  104 B,  104 C and  104 D, the etch stop layer  124  and the dielectric layer  126  are exposed. In some embodiments, a planarization process is performed to remove the protection material layer  130  outside the recesses  110 A and  110 B. The planarization process may include a CMP process, a grinding process, an etching process, another applicable process, or a combination thereof. 
     In some embodiments, the remaining portions of the protection material layer  130  in the recesses  110 A and  110 B respectively form protection layers  130 A and  130 B. In some embodiments, the protection layer  130 A is over the protection layer  128 A in the recess  110 A. In some embodiments, the protection layer  130 A is in direct contact with the sidewalls of the spacer elements  104 A and  104 B. In some embodiments, the protection layer  130 B is over the protection layer  128 B in the recess  110 B. In some embodiments, the protection layer  130 B is in direct contact with the sidewalls of the spacer elements  104 C and  104 D. 
     In some embodiments, a contact plug, which is electrically connected to the source or drain structure  122 , will be formed in a subsequent process. In some cases, the position shift in the subsequently formed contact plug may arise due to process variation. In accordance with some embodiments, the protection layer  130 A, which covers the gate structure  106 A, prevents the gate structure  106 A from being electrically connected to the shifted contact plug. In some embodiments, the protection layer  130 B, which covers the gate structure  106 B, prevents the gate structure  106 B from being electrically connected to the shifted contact plug. 
     In some embodiments, as mentioned above, the work function layers  114 A and  116 A and the gate electrode layer  118 A of the gate structure  106 A are covered by the protection layer  128 A. The work function layers  114 B,  116 B and  120 B and the gate electrode layer  118 B are covered by the protection layer  128 B. As a result, the work function layers  114 A,  114 B,  116 A,  116 B and  120 B and the gate electrode layers  118 A and  118 B are isolated from plasma during the plasma deposition process of the protection material layer  130 . 
     In accordance with some embodiments, the work function layers  114 A,  114 B,  116 A,  116 B and  120 B and the gate electrode layers  118 A and  118 B are not in direct contact with plasma during the formation of the protection layers  128 A,  128 B,  130 A and  130 B. Current leakage through the gate structures  106 A and  106 B is reduced or eliminated. Accordingly, the breakdown voltage of the semiconductor device structure is improved, and the reliability of the device is enhanced. 
     As shown in  FIG. 1E , an inter-layer dielectric (ILD) layer  132  is deposited, in accordance with some embodiments. The ILD layer  132  is over the spacer elements  104 A,  104 B,  104 C and  104 D, the etch stop layer  124 , the dielectric layer  126  and the protection layers  130 A and  130 B. In some embodiments, the ILD layer  132  is made of silicon oxide, silicon nitride, silicon oxynitride, borosilicate glass (BSG), phosphoric silicate glass (PSG), borophosphosilicate glass (BPSG), fluorinated silicate glass (FSG), SOG, high density plasma (HDP) deposition dielectric material, low-k material, another suitable material, or a combination thereof. In some embodiments, the ILD layer  132  is deposited using a CVD process, a spin-on process, an HDPCVD process, another applicable process, or a combination thereof. 
     As shown in  FIG. 1F , a contact plug  134  is formed in the ILD layer  132 , in accordance with some embodiments. As a result, a semiconductor device structure  100  is formed. The contact plug  134  provides an electrical connection between the source or drain structure  122  and a subsequently formed multi-layer interconnection (MLI). In some embodiments, the contact plug  134  includes aluminum, tungsten, copper, gold, platinum, cobalt, another suitable metal material, an alloy thereof, or a combination thereof. In some embodiments, the ILD layer  132 , the etch stop layer  124  and the dielectric layer  126  are etched to form an opening. Afterwards, a conductive material fills the opening to form the contact plug  134 . 
     It should be noted that the embodiments shown in  FIGS. 1A-1F  are merely examples, and embodiments of the disclosure are not limited thereto. Many variations and/or modifications can be made to embodiments of the disclosure. In some other embodiments, a semiconductor device structure has a protection layer having an arrangement different than that of the protection layers  128 A and  128 B. Examples of the protection layer are shown in  FIGS. 2A-2E, 3A-3F, 4A, 4B, and 5A-5D , which will be described in more detail later. 
     It should be noted that the same reference numeral in  FIGS. 1A-1F, 2A-2E, 3A-3F, 4A, 4B, and 5A-5D  is designated the same feature or similar features, for example, the protection material layer  130 , the ILD layer  132  and the contact plug  134 . The material and formation method of the same feature or similar features are as described in the embodiments of  FIGS. 1A-1F , and are not repeated hereafter for the purpose of simplicity. 
       FIGS. 2A-2E  are cross-sectional views of various stages of a process for forming a semiconductor device structure, in accordance with some embodiments. As shown in  FIG. 2A , a protection material layer  128  is deposited over the spacer elements  104 A,  104 B,  104 C and  104 D, the etch stop layer  124  and the dielectric layer  126 , in accordance with some embodiments. In some embodiments, the protection material layer  128  is further deposited over the top surface of the gate structure  106 A in the recess  110 A and the sidewalls of the spacer elements  104 A and  104 B in the recess  110 A. In some embodiments, the protection material layer  128  is further deposited over the top surface of the gate structure  106 B in the recess  110 B and the sidewalls of the spacer elements  104 C and  104 D in the recess  110 B. In some embodiments, the protection material layer  128  is deposited substantially conformally. 
     In some embodiments, the protection material layer  128  includes a dielectric material. In some embodiments, the dielectric material includes silicon oxide, silicon oxycarbide, silicon nitride, nitrogen silicon carbide, another suitable material, or a combination thereof. 
     In some embodiments, the protection material layer  128  is deposited using a substantial non-plasma deposition process. For example, the substantial non-plasma deposition process may be a non-plasma CVD process, a non-plasma ALD process, a non-plasma thermal deposition process, another applicable process, or a combination thereof. 
     In some embodiments, the substantial non-plasma CVD process includes a low pressure CVD (LPCVD) process, a low temperature CVD (LTCVD) process, a rapid thermal CVD (RTCVD) process, another applicable process, or a combination thereof. In some embodiments, the substantial non-plasma thermal deposition process includes introducing a gaseous precursor for forming the protection material layer  128  to the structure shown in  FIG. 1A . Afterwards, the gaseous precursor reacts by performing a thermal treatment. As a result, as shown in  FIG. 2A , the protection material layer  128  is deposited over the structure shown in  FIG. 1A . 
     As shown in  FIG. 2B , a protection material layer  130  is deposited over the protection material layer  128 , in accordance with some embodiments. In some embodiments, the protection material layer  130  fills up the recesses  110 A and  110 B. 
     In some embodiments, the protection material layer  130  includes a dielectric material. In some embodiments, the dielectric material includes silicon oxide, silicon oxycarbide, silicon nitride, nitrogen silicon carbide, another suitable material, or a combination thereof. In some embodiments, the protection material layer  130  is deposited using a plasma-involved deposition process, another applicable process, or a combination thereof. For example, the plasma-involved deposition process may be a PECVD process or another applicable process. 
     As shown in  FIG. 2C , the protection material layers  128  and  130  outside the recesses  110 A and  110 B are removed, in accordance with some embodiments. In some embodiments, the protection material layers  128  and  130  are partially removed until the spacer elements  104 A,  104 B,  104 C and  104 D, the etch stop layer  124  and the dielectric layer  126  are exposed. In some embodiments, a planarization process is performed to remove the protection material layers  128  and  130  outside the recesses  110 A and  110 B. The planarization process may include a CMP process, a grinding process, an etching process, another applicable process, or a combination thereof. 
     As shown in  FIG. 2C , the remaining portions of the protection material layers  128  and  130  in the recess  110 A respectively form protection layers  128 A and  130 A, in accordance with some embodiments. In some embodiments, the protection layer  128 A covers the sidewalls of the spacer elements  104 A and  104 B. In some embodiments, the protection layer  128 A is in direct contact with the sidewalls of the spacer elements  104 A and  104 B. In some embodiments, the protection layer  128 A covers the gate dielectric layer  112 A, the work function layers  114 A and  116 A, and the gate electrode layer  118 A of the gate structure  106 A. 
     In some embodiments, the protection layer  130 A is over the protection layer  128 A in the recess  110 A. In some embodiments, a part of the protection layer  128 A is sandwiched between the protection layer  130 A and the spacer element  104 A or  104 B. In some embodiments, the protection layer  130 A is separated from the spacer elements  104 A and  104 B without being in direct contact with the sidewalls of the spacer elements  104 A and  104 B. 
     As shown in  FIG. 2C , the remaining portions of the protection material layers  128  and  130  in the recess  110 B respectively form protection layers  128 B and  130 B, in accordance with some embodiments. In some embodiments, the protection layer  128 B covers the sidewalls of the spacer elements  104 C and  104 D. In some embodiments, the protection layer  128 B is in direct contact with the sidewalls of the spacer elements  104 C and  104 D. In some embodiments, the protection layer  128 B covers the gate dielectric layer  112 B, the work function layers  114 B,  116 B and  120 B and the gate electrode layer  118 B of the gate structure  106 B. 
     In some embodiments, the protection layer  130 B is over the protection layer  128 B in the recess  110 B. In some embodiments, a part of the protection layer  128 B is sandwiched between the protection layer  130 B and the spacer element  104 C or  104 D. In some embodiments, the protection layer  130 B is separated from the spacer elements  104 C and  104 D without being in direct contact with the sidewalls of the spacer elements  104 C and  104 D. 
     In some embodiments, the protection layers  128 A,  128 B,  130 A and  130 B are made of substantially the same material. However, embodiments of the disclosure are not limited thereto. In some other embodiments, the material of the protection layers  128 A and  128 B is different from that of the protection layers  130 A and  130 B. 
     As shown in  FIG. 2D , the ILD layer  132  is deposited over the spacer elements  104 A,  104 B,  104 C and  104 D, the etch stop layer  124 , the dielectric layer  126  and the protection layers  128 A,  128 B,  130 A and  130 B, in accordance with some embodiments. 
     As shown in  FIG. 2E , the contact plug  134  is formed in the ILD layer  132 , in accordance with some embodiments. As a result, a semiconductor device structure  200  is formed. 
       FIGS. 3A-3F  are cross-sectional views of various stages of a process for forming a semiconductor device structure, in accordance with some embodiments. As shown in  FIG. 3A , a protection material layer  128  is deposited over the spacer elements  104 A,  104 B,  104 C and  104 D, the etch stop layer  124  and the dielectric layer  126 , in accordance with some embodiments. In some embodiments, various processes similar to those shown in  FIG. 2A  are performed to form the protection material layer  128 . In some embodiments, the protection material layer  128  is deposited using a substantial non-plasma deposition process. 
     In some embodiments, the protection material layer  128  is further deposited over the top surface of the gate structure  106 A in the recess  110 A and the sidewalls of the spacer elements  104 A and  104 B in the recess  110 A. In some embodiments, the protection material layer  128  is further deposited over the top surface of the gate structure  106 B in the recess  110 B and the sidewalls of the spacer elements  104 C and  104 D in the recess  110 B. 
     In some embodiments, the protection material layer  128  is deposited substantially conformally. In some embodiments, the protection material layer  128  is deposited using a substantial non-plasma deposition process. 
     As shown in  FIG. 3B , a protection material layer  136  is formed in a surface portion of the protection material layer  128 , in accordance with some embodiments. In some embodiments, the protection material layer  136  is formed in the surface portion of the protection material layer  128 , which is outside the recesses  110 A and  110 B. In some embodiments, the protection material layer  136  is formed in the surface portion of the protection material layer  128 , which is over the gate structure  106 A in the recess  110 A and the gate structure  106 B in the recess  110 B. 
     In accordance with some embodiments, a surface treatment is used to form the protection material layer  136 . In some embodiments, the surface portion of the protection material layer  128  is treated with plasma to form the protection material layer  136  at the top surface of the protection material layer  128 . As a result, the surface portion of the protection material layer  128  becomes compact and denser, and then is transferred to the protection material layer  136 . 
     The surface treatment may be used to reduce the etching rate of the surface portion of the protection material layer  128 . In some embodiments, the protection material layer  136  has a greater etch resistivity than the protection material layer  128 . In some embodiments, the protection material layer  136  has an etching rate less than that of the protection material layer  128 . The protection material layer  136  is etched much slower than the protection material layer  128 . 
     In some embodiments, the surface treatment includes a plasma process, another applicable process, or a combination thereof. The plasma process may include a plasma bombardment treatment, a densification plasma treatment, or another plasma-involved treatment. 
     In some embodiments, the surface treatment is performed at an atmosphere containing an inert gas, such as argon (Ar) or another suitable gas. In some embodiments, the surface portion or top portion of the protection material layer  128  is treated with an argon-containing plasma or another suitable plasma. 
     A portion of the protection material layer  128 , which covers the sidewalls of the spacer elements  104 A,  104 B,  104 C and  104 D in the recesses  110 A and  110 B, is removed, as shown in  FIG. 3C  in accordance with some embodiments. In some embodiments, the protection material layer  128  is partially removed using an etching process, another applicable process, or a combination thereof. In some embodiments, the etching process includes a wet etching process or another applicable process. In some embodiments, a portion of the protection material layer  128 , which is protected and covered by the protection material layer  136 , remains over the gate structures  106 A and  106 B after the etching process, as shown in  FIG. 3C . 
     As shown in  FIG. 3D , a protection material layer  130  is deposited over the protection material layers  128  and  136 , in accordance with some embodiments. In some embodiments, the protection material layer  130  fills up the recesses  110 A and  110 B. In some embodiments, the protection material layer  130  is deposited using a plasma-involved deposition process, another applicable process, or a combination thereof. 
     As shown in  FIG. 3E , the protection material layers  128 ,  130  and  136  outside the recesses  110 A and  110 B are removed, in accordance with some embodiments. In some embodiments, the protection material layers  128 ,  130  and  136  are partially removed until the spacer elements  104 A,  104 B,  104 C and  104 D, the etch stop layer  124  and the dielectric layer  126  are exposed. In some embodiments, a planarization process is performed to remove the protection material layers  128 ,  130  and  136  outside the recesses  110 A and  110 B. The planarization process may include a CMP process, a grinding process, an etching process, another applicable process, or a combination thereof. 
     As shown in  FIG. 3E , the remaining portions of the protection material layers  128 ,  130  and  136  in the recess  110 A respectively form protection layers  128 A,  130 A and  136 A, in accordance with some embodiments. In some embodiments, the protection layer  136 A is sandwiched between the protection layers  128 A and  130 A. In some embodiments, the protection layers  128 A and  136 A are spaced apart from the sidewalls of the spacer elements  104 A and  104 B. In some embodiments, the protection layer  130 A is in direct contact with the sidewalls of the spacer elements  104 A and  104 B. 
     In some embodiments, the protection layers  128 A and  136 A cover the gate dielectric layer  112 A, the work function layers  114 A and  116 A and the gate electrode layer  118 A of the gate structure  106 A. In some embodiments, the protection layers  128 A and  136 A partially cover the gate dielectric layer  112 A. 
     As shown in  FIG. 3E , the remaining portions of the protection material layers  128 ,  130  and  136  in the recess  110 B respectively form protection layers  128 B,  130 B and  136 B, in accordance with some embodiments. In some embodiments, the protection layer  136 B is sandwiched between the protection layers  128 B and  130 B. In some embodiments, the protection layers  128 B and  136 B are spaced apart from the sidewalls of the spacer elements  104 C and  104 D. In some embodiments, the protection layer  130 B is in direct contact with the sidewalls of the spacer elements  104 C and  104 D. 
     In some embodiments, the protection layers  128 B and  136 B cover the gate dielectric layer  112 B, the work function layers  114 B,  116 B and  120 B and the gate electrode layer  118 B of the gate structure  106 B. In some embodiments, the protection layers  128 B and  136 B partially cover the gate dielectric layer  112 B. 
     In accordance with some embodiments, the protection layers  136 A and  136 B with a greater etch resistivity respectively cover the gate structures  106 A and  106 B. Accordingly, the protection layers  136 A and  136 B over the protection layers  128 A and  128 B provide further prevention of the gate structures  106 A and  106 B from being electrically connected to a shifted contact plug. 
     Afterwards, multiple processes similar to those shown in  FIGS. 2D and 2E  are performed. As shown in  FIG. 3F , the ILD layer  132  is deposited over the spacer elements  104 A,  104 B,  104 C and  104 D, the etch stop layer  124 , the dielectric layer  126  and the protection layers  128 A,  128 B,  130 A,  130 B,  136 A and  136 B, in accordance with some embodiments. The contact plug  134  is then formed in the ILD layer  132 . As a result, a semiconductor device structure  300  is formed. 
       FIGS. 4A and 4B  are cross-sectional views of various stages of a process for forming a semiconductor device structure, in accordance with some embodiments. As shown in  FIG. 4A , a protection material layer  138  is deposited over the protection material layer  128 , in accordance with some embodiments. In some embodiments, the protection material layer  138  fills the recesses  110 A and  110 B. In some embodiments, the protection material layer  138  is deposited substantially conformally. 
     In some embodiments, the protection material layer  138  includes a dielectric material. In some embodiments, the dielectric material includes silicon oxide, silicon oxycarbide, silicon nitride, nitrogen silicon carbide, another suitable material, or a combination thereof. 
     In accordance with some embodiments, the deposition of the protection material layer  138  includes a non-plasma process. In some embodiments, the protection material layer  128  is deposited using a non-plasma process. For example, the substantial non-plasma deposition process may be a non-plasma CVD process, a non-plasma ALD process, a non-plasma thermal deposition process, another applicable process, or a combination thereof. 
     In some embodiments, the substantial non-plasma CVD process includes a LPCVD process, a LTCVD process, a RTCVD process, another applicable process, or a combination thereof. In some embodiments, the substantial non-plasma thermal deposition process includes introducing a gaseous precursor for forming the protection material layer  138  to the protection material layer  128 . Afterwards, the gaseous precursor reacts by performing a thermal treatment. As a result, the protection material layer  138  is deposited over the protection material layer  128 , as shown in  FIG. 4A . 
     As shown in  FIG. 4B , various processes similar to those shown in  FIGS. 2B-2E  are performed to form a semiconductor device structure  400 , in accordance with some embodiments. In some embodiments, the remaining portions of the protection material layer  138  in the recesses  110 A and  110 B respectively form protection layers  138 A and  138 B. 
     In some embodiments, the protection layer  128 A is in direct contact with the sidewalls of the spacer elements  104 A and  104 B. In some embodiments, the protection layers  130 A and  138 A are separated from the spacer elements  104 A and  104 B without being in direct contact with the sidewalls of the spacer elements  104 A and  104 B. In some embodiments, the protection layer  128 A covers the gate dielectric layer  112 A, the work function layers  114 A and  116 A, and the gate electrode layer  118 A of the gate structure  106 A. In some embodiments, the protection layers  130 A and  138 A partially cover the gate dielectric layer  112 A. 
     In some embodiments, the protection layer  128 B is in direct contact with the sidewalls of the spacer elements  104 C and  104 D. In some embodiments, the protection layers  130 B and  138 B are separated from the spacer elements  104 C and  104 D without being in direct contact with the sidewalls of the spacer elements  104 C and  104 D. In some embodiments, the protection layer  128 B covers the gate dielectric layer  112 B, the work function layers  114 B,  116 B and  120 B and the gate electrode layer  118 B of the gate structure  106 B. In some embodiments, the protection layers  130 B and  138 B partially cover the gate dielectric layer  112 B. 
       FIGS. 5A-5D  are cross-sectional views of various stages of a process for forming a semiconductor device structure, in accordance with some embodiments. Similar to that shown in  FIG. 4A , the protection material layers  128  and  138  are sequentially deposited, as shown in  FIG. 5A  in accordance with some embodiments. In some embodiments, the protection material layers  128  and  138  are separately deposited using a non-plasma process. 
     Afterwards, similar to that shown in  FIG. 3B , the protection material layer  136  is formed in the surface portion of the protection material layer  128 , as shown in  FIG. 5B  in accordance with some embodiments. In some embodiments, the protection material layer  136  is formed using a surface treatment that is similar to or the same as that shown in  FIG. 3B . 
     In some embodiments, the protection material layer  136  is formed in the surface portion of the protection material layer  138 , which is outside the recesses  110 A and  110 B. In some embodiments, the protection material layer  136  is formed in the surface portion of the protection material layer  138 , which is over the gate structure  106 A in the recess  110 A and the gate structure  106 B in the recess  110 B. 
     A portion of the protection material layer  138 , which covers the sidewalls of the spacer elements  104 A,  104 B,  104 C and  104 D in the recesses  110 A and  110 B, is removed, as shown in  FIG. 5C  in accordance with some embodiments. In some embodiments, the protection material layer  138  is partially removed using an etching process, another applicable process, or a combination thereof. In some embodiments, the etching process includes a wet etching process or another applicable process. 
     As shown in  FIG. 5D , various processes similar to those shown in  FIGS. 3D-3F  are performed to form a semiconductor device structure  500 , in accordance with some embodiments. In some embodiments, the remaining portions of the protection material layer  136  in the recesses  110 A and  110 B respectively form protection layers  136 A and  136 B. 
     As shown in  FIG. 5D , the protection layer  136 A is sandwiched between the protection layers  138 A and  130 A, in accordance with some embodiments. In some embodiments, the protection layer  136 B is sandwiched between the protection layers  138 B and  130 B. 
     As shown in  FIG. 5D , in some embodiments, the protection layer  130 A is in direct contact with the sidewalls of the spacer elements  104 A and  104 B. In some embodiments, the protection layers  128 A,  136 A and  138 A are separated from the spacer elements  104 A and  104 B without being in direct contact with the sidewalls of the spacer elements  104 A and  104 B. 
     As shown in  FIG. 5D , in some embodiments, the protection layer  130 B is in direct contact with the sidewalls of the spacer elements  104 C and  104 D. In some embodiments, the protection layers  128 B,  136 B and  138 B are separated from the spacer elements  104 C and  104 D without being in direct contact with the sidewalls of the spacer elements  104 C and  104 D. 
     As shown in  FIG. 5D , in some embodiments, the protection layers  128 A,  136 A and  138 A cover the gate dielectric layer  112 A, the work function layers  114 A and  116 A, and the gate electrode layer  118 A of the gate structure  106 A. In some embodiments, the protection layers  128 B,  136 B and  138 B cover the gate dielectric layer  112 B, the work function layers  114 B,  116 B and  120 B and the gate electrode layer  118 B of the gate structure  106 B. 
     Embodiments of the disclosure form a semiconductor device structure with a gate structure in contact with spacer elements. A protection layer is formed over the gate structure and between the spacer elements. A dielectric layer is formed over the protection layer, so that a portion of the dielectric layer is between sidewalls of the spacer elements and sidewalls of the first protection layer. Due to the protection layer, the gate structure is prevented from being damaged during subsequent formation of the dielectric layer. As a result, current leakage via the gate structure, which may be the result of plasma-induced damage to the gate structure, is reduced or eliminated. Accordingly, the breakdown voltage of the semiconductor device structure is improved. Therefore, the performance and reliability of the semiconductor device structure is greatly enhanced. 
     Embodiments of the disclosure can be applied to not only a semiconductor device structure with planar FETs but also a semiconductor device structure with FinFETs. Furthermore, embodiments of the disclosure are not limited and may be applied to fabrication processes for any suitable technology generation. Various technology generations include a 20 nm node, a 16 nm node, a 10 nm node, or another suitable node. 
     In accordance with some embodiments, a semiconductor device structure includes a gate structure over a semiconductor substrate. The gate structure includes a gate electrode layer and a gate dielectric layer covering a bottom surface and sidewalls of the gate electrode layer. The semiconductor device structure also includes spacer elements in contact with sidewalls of the gate structure and protruding from a top surface of the gate electrode layer. The semiconductor device structure also includes a first protection layer over the gate electrode layer and between the spacer elements. The semiconductor device structure also includes a dielectric layer over the first protection layer and between the spacer elements. A portion of the dielectric layer is between sidewalls of the spacer elements and sidewalls of the first protection layer. 
     In accordance with some embodiments, a semiconductor device structure includes a first protection material layer over a gate structure. The semiconductor device structure also includes a second protection material layer over the first protection material layer. The semiconductor device structure also includes a dielectric material layer over the second protection layer. Sidewalls of the first protection material layer and sidewalls of the second protection material layer are in contact with the dielectric material layer. The semiconductor device structure also includes two adjacent spacer elements in contact with sidewalls of the gate structure and sidewalls of the dielectric material layer. 
     In accordance with some embodiments, a semiconductor device structure includes two adjacent spacer elements. The semiconductor device structure also includes a gate structure including a gate electrode layer and a gate dielectric layer that is between and in contact with the gate electrode layer and the two adjacent spacer elements. The semiconductor device structure also includes a first protection material layer over the gate electrode layer. At least a portion of a top surface of the gate dielectric layer is exposed from the first protection material layer. The semiconductor device structure also includes a second protection material layer covering a top surface and sidewalls the first protection material layer. The second protection material layer has sidewalls between the first protection material layer and the two adjacent spacer elements. 
     The foregoing outlines features of several embodiments so that those skilled in the art may better understand the aspects of the present disclosure. Those skilled in the art should appreciate that they may readily use the present disclosure as a basis for designing or modifying other processes and structures for carrying out the same purposes and/or achieving the same advantages of the embodiments introduced herein. Those skilled in the art should also realize that such equivalent constructions do not depart from the spirit and scope of the present disclosure, and that they may make various changes, substitutions, and alterations herein without departing from the spirit and scope of the present disclosure.