Patent Publication Number: US-8970015-B2

Title: Method for protecting a gate structure during contact formation

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation of U.S. application Ser. No. 13/944,335, which was filed on Jul. 17, 2013, now allowed, which is a divisional of U.S. application Ser. No. 13/475,245, filed on May 18, 2012, issued as U.S. Pat. No. 8,497,169, which is a divisional of U.S. application Ser. No. 12/428,011, filed Apr. 22, 2009, issued as U.S. Pat. No. 8,202,776, the entire disclosure of which is incorporated herein by reference. 
    
    
     BACKGROUND 
     The semiconductor integrated circuit (IC) industry has experienced rapid growth. Technological advances in IC materials and design have produced generations of ICs where each generation has smaller and more complex circuits than the previous generation. Conventional IC processing involves forming one or more contacts to various features of an IC. For example, oftentimes, contact openings are simultaneously formed to areas of a substrate (or wafer) (e.g., doped regions) and gate structures disposed thereover. It has been observed that the traditional processes for forming contact openings to the substrate and gate structures may result in etching portions of the gate structure, such as the gate stack (e.g., a polysilicon and/or gate electrode). This over-etching of the gate structure can lead to undesirable contact resistance and degrade device performance. 
     Accordingly, what is needed is a method for manufacturing an integrated circuit device that addresses the above stated issues. 
     SUMMARY 
     A semiconductor device and method for manufacturing a semiconductor device is disclosed. In one embodiment, the method includes providing a substrate and forming at least one gate structure over the substrate and forming a plurality of doped regions in the substrate. The method further comprises forming an etch stop layer over the substrate; removing a first portion of the etch stop layer, wherein a second portion of the etch stop layer remains over the plurality of doped regions; forming a hard mask layer over the substrate; and removing a first portion of the hard mask layer, wherein a second portion of the hard mask layer remains over the at least one gate structure. The method can further comprise forming a first contact through the second portion of the hard mask layer to the at least one gate structure, and a second contact through the second portion of the etch stop layer to the plurality of doped regions. 
     In one embodiment, the method includes providing a substrate and forming at least one gate structure over the substrate, wherein the at least one gate structure comprises a dummy gate. The method further comprises forming an etch stop layer over the substrate, including over the at least one gate structure; forming a first interlevel dielectric (ILD) layer over the etch stop layer; and performing a chemical mechanical polishing (CMP) process on the first ILD and etch stop layer until a top portion of the at least one gate structure is exposed. The method can further comprise replacing the dummy gate of the at least one gate structure; forming a hard mask layer over the top portion of the at least one gate structure; forming a second ILD layer over the first ILD layer, including over the hard mask layer; and forming one or more contact openings to the at least one gate structure and to the substrate. 
     In one embodiment, the semiconductor device includes a substrate having at least one gate structure disposed thereover and a plurality of doped regions disposed therein; a hard mask layer disposed over the at least one gate structure; an etch stop layer disposed over the plurality of doped regions; a dielectric layer disposed over the hard mask layer and etch stop layer; and one or more contacts, wherein at least one contact extends through the dielectric layer and the hard mask layer to the at least one gate structure, and wherein at least one contact extends through the dielectric layer and the etch stop layer to the plurality of doped regions. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The present disclosure is best understood from the following detailed description when read with the accompanying figures. It is emphasized that, in accordance with the standard practice in the industry, various features are not drawn to scale and are used for illustration purposes only. In fact, the dimensions of the various features may be arbitrarily increased or reduced for clarity of discussion. 
         FIG. 1  is a flow chart of a method for fabricating an integrated circuit device according to aspects of the present embodiments; and 
         FIGS. 2A-2N  are various cross-sectional views of embodiments of an integrated circuit device during various fabrication stages according to the method of  FIG. 1 . 
     
    
    
     DETAILED DESCRIPTION 
     The present disclosure relates generally to methods for manufacturing integrated circuit devices, and more particularly, to a method for manufacturing an integrated circuit device with improved device performance. 
     It is understood that the following disclosure provides many different embodiments, or examples, for implementing different features of the invention. 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. 
     With reference to  FIGS. 1 through 2N , a method  100  and a semiconductor device  200  are collectively described below.  FIG. 1  is a flow chart of one embodiment of the method  100  for making the semiconductor device  200 .  FIGS. 2A-2N  are various cross-sectional views of the semiconductor device  200  according to one embodiment, in portion or entirety, during various fabrication stages of the method  100 . The semiconductor device  200  may be an integrated circuit, or portion thereof, that may comprise static random access memory (SRAM), memory cells, and/or logic circuits; passive components such as resistors, capacitors, inductors, and/or fuses; active components, such as P-channel field effect transistors (PFETs), N-channel field effect transistors (NFETs), metal-oxide-semiconductor field effect transistors (MOSFETs), complementary metal-oxide-semiconductor transistors (CMOSs), bipolar transistors, high voltage transistors, and/or high frequency transistors; other suitable components; and/or combinations thereof. It is understood that additional steps can be provided before, during, and after the method  100 , and some of the steps described below can be replaced or eliminated, for additional embodiments of the method  100 . It is further understood that additional features can be added in the semiconductor device  200 , and some of the features described below can be replaced or eliminated, for additional embodiments of the semiconductor device  200 . 
     The semiconductor device  200  may be fabricated in a gate first process, gate last process, or hybrid process including a gate first process and a gate last process. In the gate first process, a metal gate structure may be formed first and may be followed by a CMOS process flow to fabricate the final device. In the gate last process, a dummy poly gate structure may be formed first and may be followed by a normal CMOS process flow until deposition of an interlayer dielectric (ILD), and then the dummy poly gate structure may be removed and replaced with a metal gate structure. In the hybrid gate process, a metal gate structure of one type of device may be formed first and a metal gate structure of another type of device may be formed last. 
     Referring to  FIGS. 1 and 2A , the method  100  begins at step  102  wherein a substrate  210  including at least one isolation region  212  is provided. In the present embodiment, the substrate  210  is a semiconductor substrate. The semiconductor substrate  210  may comprise an elementary semiconductor including silicon or germanium in crystal, polycrystalline, or an amorphous structure; a compound semiconductor including silicon carbide, gallium arsenic, gallium phosphide, indium phosphide, indium arsenide, and/or indium antimonide; an alloy semiconductor including SiGe, GaAsP, AlInAs, AlGaAs, GaInAs, GaInP, and/or GaInAsP; any other suitable material; and/or combinations thereof. In one embodiment, the alloy semiconductor substrate may have a gradient SiGe feature in which the Si and Ge composition change from one ratio at one location to another ratio at another location of the gradient SiGe feature. In another embodiment, the alloy SiGe is formed over a silicon substrate. In another embodiment, a SiGe substrate is strained. Furthermore, the semiconductor substrate may be a semiconductor on insulator, such as a silicon on insulator (SOI), or a thin film transistor (TFT). In some examples, the semiconductor substrate may include a doped epi layer or a buried layer. In other examples, the compound semiconductor substrate may have a multilayer structure, or the silicon substrate may include a multilayer compound semiconductor structure. In some embodiments, the substrate  210  may comprise a non-semiconductor material, such as glass. 
     The substrate  210  may include various doping configurations depending on design requirements as known in the art. In some embodiments, the substrate  210  may include doped regions. The doped regions may be doped with p-type or n-type dopants. For example, the doped regions may be doped with p-type dopants, such as boron or BF 2 ; n-type dopants, such as phosphorus or arsenic; and/or combinations thereof. The doped regions may be formed directly on the semiconductor substrate, in a P-well structure, in a N-well structure, in a dual-well structure, or using a raised structure. The semiconductor substrate  210  may further include various active regions, such as regions configured for an N-type metal-oxide-semiconductor transistor device (referred to as an NMOS) and regions configured for a P-type metal-oxide-semiconductor transistor device (referred to as a PMOS). It is understood that the semiconductor device  200  may be formed by complementary metal-oxide-semiconductor (CMOS) technology processing, and thus some processes are not described in detail herein. 
     The at least one isolation region  212  may be formed on the substrate  210  to isolate various regions, for example, to isolate NMOS and PMOS transistor device regions. The isolation region  212  may utilize isolation technology, such as local oxidation of silicon (LOCOS) or shallow trench isolation (STI), to define and electrically isolate the various regions. In the present embodiment, the isolation region  212  includes a STI. The isolation region  212  may comprise silicon oxide, silicon nitride, silicon oxynitride, fluoride-doped silicate glass (FSG), a low-K dielectric material, other suitable materials, and/or combinations thereof. The isolation region  212 , and in the present embodiment, the STI, may be formed by any suitable process. As one example, the formation of an STI may include patterning the semiconductor substrate by a conventional photolithography process, etching a trench in the substrate (for example, by using a dry etching, wet etching, and/or plasma etching process), and filling the trench (for example, by using a chemical vapor deposition process) with a dielectric material. In some embodiments, the filled trench may have a multi-layer structure such as a thermal oxide liner layer filled with silicon nitride or silicon oxide. 
     Referring to FIGS.  1  and  2 A- 2 B, at step  104 , at least one gate structure  220  is formed over the substrate  210 . The gate structure  220  may be formed by any suitable process. For example, the gate structure  220  may be formed by conventional deposition, photolithography patterning, and etching processes, and/or combinations thereof. The deposition processes may include chemical vapor deposition (CVD), physical vapor deposition (PVD), atomic layer deposition (ALD), high density plasma CVD (HDPCVD), metal organic CVD (MOCVD), remote plasma CVD (RPCVD), plasma enhanced CVD (PECVD), epitaxial growth methods (e.g., selective epitaxy growth), sputtering, plating, spin-on coating, other suitable methods, and/or combinations thereof. The photolithography patterning processes may include photoresist coating (e.g., spin-on coating), soft baking, mask aligning, exposure, post-exposure baking, developing the photoresist, rinsing, drying (e.g., hard baking), other suitable processes, and/or combinations thereof. The photolithography exposing process may also be implemented or replaced by other proper methods such as maskless photolithography, electron-beam writing, ion-beam writing, and/or molecular imprint. The etching processes may include dry etching, wet etching, and/or other etching methods (e.g., reactive ion etching). The etching process may also be either purely chemical (plasma etching), purely physical (ion milling), and/or combinations thereof. It is understood that the at least one gate structure may be formed by any combination of the processes described herein. 
     In the present embodiment, referring to  FIG. 2A , a gate stack comprising a high-k dielectric layer  222  and a dummy gate layer  224  is formed. The high-k dielectric layer  222  is formed over the substrate  210 . The high-k dielectric layer  222  may include hafnium oxide (HfO 2 ), hafnium silicon oxide (HfSiO), hafnium silicon oxynitride (HfSiON), hafnium tantalum oxide (HfTaO), hafnium titanium oxide (HfTiO), hafnium zirconium oxide (HfZrO), metal oxides, metal nitrides, metal silicates, transition metal-oxides, transition metal-nitrides, transition metal-silicates, oxynitrides of metals, metal aluminates, zirconium silicate, zirconium aluminate, silicon oxide, silicon nitride, silicon oxynitride, zirconium oxide, titanium oxide, aluminum oxide, hafnium dioxide-alumina (HfO 2 —Al 2 O 3 ) alloy, other suitable high-k dielectric materials, and/or combinations thereof. 
     In the present embodiment, the dummy gate layer  224  comprises polycrystalline silicon. The gate stack may be formed by any suitable process, including the processes described herein. In one example, the high-k dielectric layer  222  and dummy gate layer  224  are deposited over the substrate  210 . Then, a layer of photoresist is formed over the dummy gate layer  224  by a suitable process, such as spin-on coating, and patterned to form a patterned photoresist feature by a proper lithography patterning method. Antireflective coating layers (e.g., a top antireflective coating layer and/or a bottom antireflective coating layer) may be formed adjacent the layer of photoresist. The pattern of the photoresist can then be transferred by a dry etching process to the underlying layers (i.e., the high-k dielectric layer  222  and the dummy gate layer  224 ) to form the gate stack as shown in  FIG. 2A . The photoresist layer may be stripped thereafter. In another example, a hard mask layer is formed over the dummy gate layer  224 ; a patterned photoresist layer is formed on the hard mask layer; the pattern of the photoresist layer is transferred to the hard mask layer and then transferred to the dummy gate layer  224  and the high-k dielectric layer  222  to form the gate stack of the gate structure  220 . It is understood that the above examples do not limit the processing steps that may be utilized to form the gate stack  220 . It is further understood that the gate stack of the gate structure  220  may comprise additional layers. For example, the gate stack may additionally include an interfacial layer, such as silicon oxide, interposed between the substrate  210  and the high-k dielectric layer  222 . In another embodiment, the gate stack may comprise a capping layer interposed between the dummy gate layer  224  and the high-k dielectric layer  222 . 
     A sealing layer  225  is formed on the sidewalls of the gate stack of the gate structure  220 . In the present embodiment, the sealing layer  225  is formed on the sidewalls of the high-k dielectric layer  222  and dummy gate layer  224 . The sealing layer  225  may include a dielectric material, such as silicon nitride, silicon oxide, silicon oxynitride, other suitable material, and/or combinations thereof. The sealing layer  225  may include a single layer or multiple layer configuration. It should be noted that the sealing layer  225  may protect the gate stack of the gate structure  220  from damage or loss during subsequent processing, and may also prevent oxidation during subsequent processing. The sealing layer  225  is formed by any suitable process to any suitable thickness, including the processes described herein. 
     Referring to  FIG. 2B , lightly doped source/drain (LDD) regions  226  are formed. The LDD regions  226  may be formed in the substrate  210  by one or more implantation processes, such as an ion implantation process. The doping species may depend on the type of device being fabricated, such as an NMOS or PMOS device. For example, the LDD regions  226  may be doped with p-type dopants, such as boron or BF 2 ; n-type dopants, such as phosphorus or arsenic; and/or combinations thereof. The LDD regions  226  may comprise various doping profiles. The LDD regions  226  may be aligned with an outer edge of the sealing layer  225  following the ion implantation process. As previously noted, the sealing layer  225  may provide protection to prevent contamination or damage to the gate stack comprising the high-k dielectric layer  222  and dummy gate layer  224  during subsequent processing. Thus, the integrity of the gate structure  220  may be maintained which may result in better device performance and reliability. Additionally, it should be noted that during a subsequent annealing process (e.g., activation process) the dopants in the LDD regions  226  may diffuse towards the sidewalls of the gate stack comprising the high-k dielectric layer  222  and dummy gate layer  224  such that a portion of each of the LDD regions  226  may extend underneath a portion of the sealing layer  225 . 
     Following formation of the LDD regions  226 , conventional spacer liner  227 , gate spacers  228 , and S/D regions  230  are formed. The spacer liner  227  and gate spacers  228  are formed by any suitable process to any suitable thickness, including the processes described herein. In the present embodiment, the spacer liner  227  comprise an oxide material (e.g., silicon oxide), and the gate spacers  228 , which are positioned on each side of the gate structure  220 , comprise a nitride material (e.g., silicon nitride). The gate spacers  228  may comprise a dielectric material such as silicon nitride, silicon oxide, silicon carbide, silicon oxynitride, other suitable materials, and/or combinations thereof. The spacer liner  227  and/or gate spacers  228  may comprise a multilayer structure. The gate spacers  228  may be used to offset the S/D regions  230  (also referred to as heavily doped source/drain regions). The S/D regions  230  may be formed in the substrate  210  by one or more implantation processes, such as an ion implantation process. The doping species may depend on the type of device being fabricated, such as an NMOS or PMOS device. For example, the S/D regions  230  may doped with p-type dopants, such as boron or BF 2 ; n-type dopants, such as phosphorus or arsenic; and/or combinations thereof. The S/D regions  230  may comprise various doping profiles, and the S/D regions  230  may be aligned with an outer edge of the spacers  228  following the ion implantation process. The S/D regions  230  may further include raised S/D regions in some embodiments. Also, one or more contact features (e.g., silicide regions) may be formed on the S/D regions  230  by a salicidation (or self-aligned silicidation) process. 
     Referring to  FIG. 2C , an etch stop layer (ESL)  232  and interlayer (or inter-level) dielectric (ILD) layer  234  may be formed over the semiconductor device  200 , including over the at least one gate structure, by any suitable process, such as CVD. The ESL  232  may include silicon nitride, silicon oxynitride, amorphous carbon material, silicon carbide and/or other suitable materials. The ESL  232  composition may be selected based upon etching selectivity to one or more additional features of the semiconductor device  200 . In the present embodiment, the ESL  232  is a contact etch stop layer (CESL) comprising silicon nitride. ESL  232  further comprises any suitable thickness. In the present embodiment, ESL  232  comprises a thickness of about 200 Å. 
     The ILD layer  234  comprises a dielectric material. The dielectric material may comprise silicon oxide, silicon nitride, silicon oxynitride, spin-on glass (SOG), fluorinated silica glass (FSG), carbon doped silicon oxide (e.g., SiCOH), Black Diamond® (Applied Materials of Santa Clara, Calif.), Xerogel, Aerogel, amorphous fluorinated carbon, Parylene, BCB (bis-benzocyclobutenes), Flare, SiLK (Dow Chemical, Midland, Mich.), polyimide, non-porous materials, porous materials, and/or combinations thereof. In some embodiments, the ILD layer  234  may include a high density plasma (HDP) dielectric material (e.g., HDP oxide) and/or a high aspect ratio process (HARP) dielectric material (e.g., HARP oxide). The ILD layer  234  comprises any suitable thickness. In the present embodiment, ILD layer  234  comprises a thickness of about 4500 Å. It is understood that the ILD layer  234  may comprise one or more dielectric materials and/or one or more dielectric layers. 
     Subsequently, the ESL  232  and/or ILD layer  234  are planarized by a chemical mechanical polishing (CMP) process until a top portion of the at least one gate structure  220  overlying the semiconductor substrate  210  is exposed as illustrated in  FIG. 2D . The CMP process may have a high selectivity to provide a substantially planar surface for the gate structure  220 , ESL  232 , and ILD layer  234 . The CMP process may also have low dishing and/or metal erosion effect. 
     Referring to  FIG. 2E  and  FIG. 2F , a gate replacement process is performed. The dummy gate layer  224  is removed and replaced by a metal gate. For example, in the present embodiment, the dummy gate layer  224  is replaced by a work function layer  236  and a gate layer  238 . The dummy gate layer  224  is removed to form a trench (or recess) in the gate structure  220  by any suitable process, including the processes described herein. The work function layer  236  and gate layer  238  may then be formed in the trench (or recess) of the gate structure  220 . The work function layer  236  is formed over the high-k dielectric layer  222 . The work function layer  236  is tuned to have a proper work function and comprises any suitable material. For example, if a P-type work function metal (P-metal) for a PMOS device is desired, TiN, WN, or W may be used. On the other hand, if an N-type work function metal (N-metal) for NMOS devices is desired, TiAl, TiAlN, or TaCN, may be used. In some embodiments, the work function layer  236  may include doped-conducting metal oxide materials. The gate layer  238  comprises a conductive material, such as aluminum, copper, tungsten, titanium, tantulum, titanium nitride, tantalum nitride, nickel silicide, cobalt silicide, TaC, TaSiN, TaCN, TiAl, TiAlN, other suitable materials, and/or combinations thereof. Further, the gate layer  238  may be doped polycrystalline silicon with the same or different doping. In the present embodiment, the gate layer  238  comprises aluminum. It is understood that additional layers may be formed above and/or below the work function layer  236  and/or gate layer  238 , including liner layers, interface layers, seed layers, adhesion layers, barrier layers, etc. It is further understood that the work function layer  236  and gate layer  238  may comprise one or more materials and/or one or more layers. The work function layer  236  and gate layer  238  may be formed by any suitable process to any suitable thickness, including the processes described herein. 
     Subsequent to the formation of the work function layer  236  and gate layer  238 , a CMP process may be performed to provide a substantially coplanar surface of the gate layer  238  (e.g., aluminum gate layer) of the gate structure  220 . Conventional processing would continue to form an ILD layer over the semiconductor device  200 , including over the gate structure; etch one or more contact openings to the S/D regions and/or the gate structure; and then, fill the one or more contact openings with a conductive material. It has been observed that formation of the one or more contact openings may undesirably etch portions of the gate stack (e.g., the gate layer). This can result since it takes longer to etch to the S/D regions than the gate stack. Thus, because the gate stack lacks protection, a top portion of the gate stack is exposed prior to a top portion of the S/D regions, which leads to portions of the gate stack being etched away. Such etching-through of the gate stack can lead to higher than desirable contact resistance, which may negatively affect overall device performance. Accordingly, in the present embodiment, a protective layer is formed over the gate structure. The protective layer may prevent the etching-through issue arising from the continued etching utilized to form contact openings to the S/D regions. 
     Referring to  FIGS. 1 and 2G , at step  106 , a hard mask (or protective) layer  240  is formed over the semiconductor device  200 . More specifically, the hard mask layer  240  is formed over the ILD layer  234 , including over the gate structure  220 . In the present embodiment, the hard mask layer  240  comprises silicon nitride. The hard mask layer  240  may include a silicon oxynitride, amorphous carbon material, silicon carbide, other suitable nitrogen-containing materials, other suitable dielectric materials, and/or combinations thereof. The hard mask layer  240  may be formed by any suitable process, such as CVD. The hard mask layer  240  may include a single layer or multiple layers. Further, the hard mask layer  240  comprises any suitable thickness. In some embodiments, the hard mask layer  240  and the ESL  232  comprise substantially a same thickness. For example, in the present embodiment, the hard mask layer  240  comprises a thickness of about 200 Å. 
     At step  108 , one or more portions of the hard mask layer are removed, wherein a portion of the hard mask layer remains over the at least one gate structure. The one or more portions of the hard mask layer  240  are removed by any suitable process, including the processes described herein. In the present embodiment, a photoresist layer  242  is formed over the hard mask layer  240  to any suitable thickness. Then, the photoresist layer  242  is patterned by a conventional photolithography process and/or processes to create one or more first portions  242 A and one or more second portions  242 B as shown in  FIG. 2H . The photolithography patterning processes may include photoresist coating (e.g., spin-on coating), soft baking, mask aligning, exposure, post-exposure baking, developing the photoresist, rinsing, drying (e.g., hard baking), other suitable processes, and/or combinations thereof. The photolithography exposing process may also be implemented or replaced by other proper methods such as maskless photolithography, electron-beam writing, ion-beam writing, and/or molecular imprint. Further, in some embodiments, the photolithography patterning and exposing process may implement krypton fluoride (KrF) excimer lasers, argon fluoride (ArF) excimer lasers, immersion lithography, extreme ultra-violet (EUV) radiation, and/or combinations thereof. It is understood that additional layers may be formed above or below the photoresist layer  242 , such as one or more antireflective coating layers. 
     The patterned photoresist layer  242  comprising first and second portions  242 A,  242 B define unprotected and protected portions of the hard mask layer  240 . The first portions  242 A define unprotected portions of the hard mask layer  240 . The second portions  242 B define protected portions of the hard mask layer  240 . The second portions  242 B pattern and define portions of the hard mask layer  240  that will remain over the at least one gate structure  220 . Referring to  FIG. 21 , the first portions  242 A of the photoresist layer  242  and the unprotected portions of the hard mask layer  240 , which underlie the first portions  242 A, are removed. The first portions  242 A and unprotected portions of the hard mask layer  240  are removed by any suitable process. It is understood that the first portions  242 A and unprotected portions of the hard mask layer  240  may be simultaneously or independently removed. For example, removing such portions may include an etching process. The etching process may include multiple etching steps and etching solutions to remove the first portions  242 A and/or unprotected portions of the hard mask layer  240 . The etching process may comprise one or more dry etching processes, wet etching processes, other suitable etching methods (e.g., reactive ion etching), and/or combinations thereof. 
     Subsequently, the photoresist layer  242  (i.e., second portions  242 B) may be removed by any suitable process, such as a photoresist stripping process. Referring to  FIG. 2J , the protected portions of the hard mask layer  240 , which were underlying second portions  242 B, remain over the substrate  210 . In the present embodiment, the hard mask layer  240  remains extending over the entirety of the gate structure  220 . It is understood that the remaining hard mask layer  240  may extend any suitable distance (for example, the hard mask layer  240  may extend over only the gate stack of the gate structure  220 ). It is further understood that the process utilized to pattern the hard mask layer  240  is not limited to the example described herein. For example, in some embodiments, a photoresist layer  242  may not be deposited over the hard mask layer  240 , and the hard mask layer  240  may be patterned by a conventional lithography process, such as utilizing a mask (e.g., a mask utilized to pattern the gate stack). 
     Referring to  FIGS. 1 and 2K , at step  110 , an ILD layer  244  is formed over the semiconductor device  200 . In the present embodiment, the ILD layer  244  is formed over the hard mask layer  240 . The ILD layer  244  comprises a dielectric material, such as silicon oxide, silicon nitride, silicon oxynitride, SOG, FSG, carbon doped silicon oxide (e.g., SiCOH), Black Diamond® (Applied Materials of Santa Clara, Calif.), Xerogel, Aerogel, amorphous fluorinated carbon, Parylene, BCB, Flare, SiLK (Dow Chemical, Midland, Mich.), polyimide, non-porous materials, porous materials, other suitable dielectric materials, and/or combinations thereof. In some embodiments, the ILD layer  244  may include a HDP oxide and/or a HARP oxide. The ILD layer  244  comprises any suitable thickness. The ILD layer  244  may comprise one or more dielectric materials and/or one or more dielectric layers. Subsequently, the ILD layer  244  may be planarized by a CMP process. 
     Referring to  FIG. 1  and  FIGS. 2L-2N , at step  112 , one or more contacts are formed to the substrate and/or at least one gate structure. In the present embodiment, one or more contacts are formed to the S/D regions  230  and the gate structure  220 . Forming the one or more contacts comprises performing a first etching process and a second etching process. The first etching process is performed on the semiconductor device  200  to remove a portion of the ILD layers  234 ,  244 . In the present embodiment, the first etching process is performed on the ILD layers  234 ,  244  until the ESL layer  232  over the S/D regions  230  and the hard mask layer  240  over the gate structure  220  is reached and/or exposed as illustrated in  FIG. 2L . The removed portions of ILD layers  234 ,  244  form first contact openings and/or trenches  246 A,  248 A to the S/D regions  230  and gate structure  220 . The first (or main) etching process has an etching selectivity between the ESL  232 /hard mask layer  240  and the ILD layers  234 ,  244 . Accordingly, the first etching process may stop at the ESL  232 /hard mask layer  240 . For example, with the ESL  232 /hard mask layer  240  comprising silicon nitride and the ILD layers  234 ,  244  comprising oxide, the first etching process may exhibit a high etching selectivity between silicon nitride and oxide, such that the first etching process removes ILD layers  234 ,  244  without substantially affecting the ESL  232 /hard mask layer  240 . 
     As is evident from  FIG. 2L  and as noted above, in conventional processing, a top portion of the gate structure  220  will be reached before a top portion of the S/D regions  230  when forming contact openings. This often results in the undesirable etching of the gate structure  220 . In the present embodiment, the hard mask layer  240  can protect the gate structure  220 , particularly the gate layer  238  of the gate structure  220 , while the first etching process forms contact openings to the ESL  232 . The hard mask layer  240  may function as an etch stop layer for the first etching process. Thus, etching portions of the gate structure  220 , such as the gate layer  238 , is prevented. Such prevention may provide improved device performance by reducing the contact resistance arising at the gate structure. 
     The second etching process is performed on the semiconductor device  200  to remove a portion of the ESL  232  and hard mask layer  240 . The second etching process is performed on the ESL layer  232  and hard mask layer  240  until a top portion of the S/D regions  230  and a top portion of the gate structure  220  (e.g., gate layer  238 ) is reached and/or exposed as illustrated in  FIG. 2M . The removed portions of ILD layers  234 ,  244  and ESL  232 /hard mask layer  240  form second contact openings and/or trenches  246 B,  248 B to the S/D regions  230  and gate structure  220 . The second etching process has an etching selectivity between the ESL  232 /hard mask layer  240  and the ILD layers  234 ,  244 . For example, with the ESL  232 /hard mask layer  240  comprising silicon nitride and the ILD layers  234 ,  244  comprising oxide, the second etching process may exhibit a high etching selectivity between silicon nitride and oxide, such that the second etching process removes ESL  232 /hard mask layer  240  without substantially affecting the ILD layers  234 ,  244 . In the present embodiment, the second etching process comprises a silicon nitride etching process. 
     The first and second etching processes may comprise one or more dry etching processes, wet etching processes, other suitable processes (e.g., reactive ion etching), and/or combinations thereof. The etching processes may be either purely chemical (plasma etching), purely physical (ion milling), and/or combinations thereof. For example, a dry etching process may be implemented in an etching chamber using process parameters including a radio frequency (RF) source power, a bias power, a pressure, a flow rate, a wafer temperature, other suitable process parameters, and/or combinations thereof. The dry etching process may implement an oxygen-containing gas, fluorine-containing gas (e.g., CF 4 , SF 6 , CH 2 F 2 , CHF 3 , and/or C 2 F 6 ), chlorine-containing gas (e.g., Cl 2 , CHCl 3 , CCl 4 , and/or BCl 3 ), bromine-containing gas (e.g., HBr and/or CHBR 3 ), iodine-containing gas, other suitable gases and/or plasmas, and/or combinations thereof. In some embodiments, the dry etching process utilizes an O 2  plasma treatment and/or an O 2 /N 2  plasma treatment. Further, the dry etching process may be performed for any suitable time. A wet etching process may utilize a hydrofluoric acid (HF) solution for a HF dipping process. The HF solution may have any suitable concentration (e.g., 1:100). In some embodiments, a wet etching process may apply a diluted hydrofluoric acid to the semiconductor device  200 . It is understood that the first and second etching processes may include multiple etching steps and etching solutions. 
     Referring to  FIG. 2N , subsequently, contacts  250 ,  252  may be formed by any suitable process, including the processes described herein. Contacts  250  provide contact to the S/D regions  230  (via silicide regions), and contact  252  provides contact to the gate structure  220  (for example, coupled to a gate electrode of the gate structure  220 ). The contacts  250 ,  252  may be formed by filling second contact openings  246 B,  248 B with a conductive material. The conductive material may comprise aluminum, copper, tungsten, titanium, tantulum, titanium nitride, tantalum nitride, nickel silicide, cobalt silicide, TaC, TaSiN, TaCN, TiAl, TiAlN, other suitable materials, and/or combinations thereof. It is understood that the semiconductor device  200  may undergo further CMOS or MOS technology processing to form various features known in the art. 
     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.