Patent Publication Number: US-2022238383-A1

Title: Non-planar i/o and logic semiconductor devices having different workfunction on common substrate

Description:
CLAIM OF PRIORITY 
     This application is a continuation of U.S. patent application Ser. No. 17/112,959, filed Dec. 4, 2020, which is a continuation of U.S. patent application Ser. No. 15/930,700, filed May 13, 2020, now U.S. Pat. No. 10,892,192, issued Jan. 12, 2021, which is a continuation of U.S. patent application Ser. No. 16/253,760, filed Jan. 22, 2019, now U.S. Pat. No. 10,692,771, issued Jun. 23, 2020, which is a continuation of U.S. patent application Ser. No. 14/914,179, filed Feb. 24, 2016, now U.S. Pat. No. 10,229,853, issued Mar. 12, 2019, which is a U.S. National Phase application under 35 U.S.C. § 371 of International Application No. PCT/US2013/062308, filed Sep. 27, 2013, entitled “NON-PLANAR I/O AND LOGIC SEMICONDUCTOR DEVICES HAVING DIFFERENT WORKFUNCTION ON COMMON SUBSTRATE” the entire contents of which are incorporated herein by reference. 
    
    
     TECHNICAL FIELD 
     Embodiments of the invention are in the field of semiconductor devices and processing and, in particular, non-planar I/O and logic semiconductor devices having different workfunctions on common substrates and methods of fabricating non-planar I/O and logic semiconductor devices having different workfunctions on common substrates. 
     BACKGROUND 
     For the past several decades, the scaling of features in integrated circuits has been a driving force behind an ever-growing semiconductor industry. Scaling to smaller and smaller features enables increased densities of functional units on the limited real estate of semiconductor chips. For example, shrinking transistor size allows for the incorporation of an increased number of memory or logic devices on a chip, lending to the fabrication of products with increased capacity. The drive for ever-more capacity, however, is not without issue. The necessity to optimize the performance of each device becomes increasingly significant. 
     In the manufacture of integrated circuit devices, multi-gate transistors, such as fin field effect transistors (fin-FETs), have become more prevalent as device dimensions continue to scale down. In conventional processes, fin-FETs are generally fabricated on either bulk silicon substrates or silicon-on-insulator substrates. In some instances, bulk silicon substrates are preferred due to their lower cost and compatibility with the existing high-yielding bulk silicon substrate infrastructure. 
     Scaling multi-gate transistors has not been without consequence, however. As the dimensions of these fundamental building blocks of microelectronic circuitry are reduced and as the sheer number of fundamental building blocks fabricated in a given region is increased, the constraints on the semiconductor processes used to fabricate these building blocks have become overwhelming. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1A  illustrates a cross-sectional view of an incomplete portion of a semiconductor structure having an I/O transistor and a logic transistor disposed on a common substrate. 
         FIG. 1B  illustrates a cross-sectional view of an incomplete portion of a semiconductor structure having an I/O transistor and a logic transistor disposed on a common substrate, in accordance with an embodiment of the present invention. 
         FIGS. 2A-2F  illustrate cross-sectional view of various operations in a method of fabricating an I/O transistor and a logic transistor on a common substrate, in accordance with an embodiment of the present invention, where: 
         FIG. 2A  illustrates an incomplete semiconductor structure having a hardmask form in gate electrode regions of a logic transistor, but not in gate electrode regions of an I/O transistor; 
         FIG. 2B  illustrates the structure of  FIG. 2A  having the portion of the workfunction metal layer at gate electrode regions of the I/O transistor removed; 
         FIG. 2C  illustrates the structure of  FIG. 2B  having a second workfunction metal layer and a second hardmask layer formed thereon; 
         FIG. 2D  illustrates the structure of  FIG. 2C  following recessing of the second hardmask layer; 
         FIG. 2E  illustrates the structure of  FIG. 2D  following removal of exposed portions of the second workfunction layer; and 
         FIG. 2F  illustrates the structure of  FIG. 2E  following removal of remaining portions of the hardmask layer and second hardmask layer. 
         FIG. 3A  illustrates a cross-sectional view of a non-planar semiconductor device, in accordance with an embodiment of the present invention. 
         FIG. 3B  illustrates a plan view taken along the a-a′ axis of the semiconductor device of  FIG. 3A , in accordance with an embodiment of the present invention. 
         FIG. 4  illustrates a computing device in accordance with one implementation of the invention. 
     
    
    
     DESCRIPTION OF THE EMBODIMENTS 
     Non-planar I/O and logic semiconductor devices having different workfunctions on common substrates and methods of fabricating non-planar I/O and logic semiconductor devices having different workfunctions on common substrates are described. In the following description, numerous specific details are set forth, such as specific integration and material regimes, in order to provide a thorough understanding of embodiments of the present invention. It will be apparent to one skilled in the art that embodiments of the present invention may be practiced without these specific details. In other instances, well-known features, such as integrated circuit design layouts, are not described in detail in order to not unnecessarily obscure embodiments of the present invention. Furthermore, it is to be understood that the various embodiments shown in the Figures are illustrative representations and are not necessarily drawn to scale. 
     One or more embodiments described herein are directed to approaches to of fabricating multiple workfunctions (WF) for different pitches of semiconductor devices fabricated on a common substrate. Applications may be in the fabrication of metal oxide semiconductor (MOS) and structures having both I/O transistors (e.g., drive transistor) and logic transistors (e.g., computation transistors) fabricated from a shared process scheme on a common substrate. In an example, the I/O transistors are fabricated to have a larger gate length and different workfunction as compared to the corresponding logic transistors. 
     To provide context, presently, the performances of different devices in system on chip (SoC) integrated circuits are controlled by different pitch, critical dimension (CD) and implant tailoring. However, all devices of a same conductivity type (e.g., N-type of P-type) typically have a same work function (WF). By contrast, one or more embodiments described herein provides an approach to patterning different work functions for different devices, enabling independent control performance of each device type. 
     More specifically, one or more embodiments take advantage of an etch rate dependence of a carbon hard mask (CHM) between different structures with different CDs (e.g., a wider CD has faster etch rate than a narrower CD). As such, different workfunction layers (such as metal gate layers) can be patterned for different devices (e.g., I/O versus logic devices). One or more embodiments, then, provide an opportunity to achieve different actual gate workfunctions for like devices (e.g., N-type devices) having differing function, e.g., an I/O device versus a logic device. By differentiating the workfunction between devices, the performance of each device can be independently targeted without use of any additional mask operations. 
     Previous approaches for providing different effective gate workfunctions for like devices (e.g., N-type devices) having differing function, e.g., an I/O device versus a logic device, have involved the use of substrate implant differentiation to control the performance of different devices. As an example,  FIG. 1A  illustrates a cross-sectional view of an incomplete portion of a semiconductor structure  100 A having an I/O transistor  102 A and a logic transistor  104 A disposed on a common substrate  101 A and separated by an inter-layer dielectric region  103 A. Referring to  FIG. 1A , the I/O transistor  102 A is formed over a first fin  106 A, and the logic transistor  104 A is formed over a second fin  108 A. In the particular example shown, the I/O transistor  102 A has three relatively wider gate electrode regions  110 A,  112 A and  114 A (cross-sectional view shows the gate length  111 A as taken between source/drain regions). The underlying fin  106 A can include epitaxial source/drain regions  116 A, as shown. Meanwhile, the logic transistor  104 A has three relatively narrower gate electrode regions  120 A,  122 A and  124 A (cross-sectional view shows the gate length  121 A as taken between source/drain regions). The underlying fin  108 A can also include epitaxial source/drain regions  126 A, as shown. 
     Referring again to  FIG. 1A , at the point of processing depicted, a replacement gate process has been performed where a dummy gate material is replaced with a workfunction metal layer  118 A at gate electrode regions  110 A,  112 A,  114 A,  120 A,  122 A and  124 A. However, the workfunction metal layer  118 A is the same for the gate electrode regions of both the I/O transistor  102 A and the logic transistor  104 A. Therefore, in order to differentiate the effective workfunction of the I/O transistor  102 A and the logic transistor  104 A, approaches such as fin doping differentiation are used. It is to be understood that additional processing can subsequently be performed to complete the devices of  FIG. 1A , such as gate fill, contact formation, and back-end of line (BEOL) interconnect fabrication. 
     In contrast to the arrangement described in association with  FIG. 1A ,  FIG. 1B  illustrates a cross-sectional view of an incomplete portion of a semiconductor structure  100 B having an I/O transistor  102 B and a logic transistor  104 B disposed on a common substrate  101 B and separated by an inter-layer dielectric region  103 B, in accordance with an embodiment of the present invention. Referring to  FIG. 1B , the I/O transistor  102 B is formed over a first fin  106 B, and the logic transistor  104 B is formed over a second fin  108 B. In the particular example shown, the I/O transistor  102 B has three relatively wider gate electrode regions  110 B,  112 B and  114 B (cross-sectional view shows the gate length  111 B as taken between source/drain regions). The underlying fin  106 B can include epitaxial source/drain regions  116 B, as shown. Meanwhile, the logic transistor  104 B has three relatively narrower gate electrode regions  120 B,  122 B and  124 B (cross-sectional view shows the gate length  121 B as taken between source/drain regions). The underlying fin  108 B can also include epitaxial source/drain regions  126 B, as shown. 
     Referring again to  FIG. 1B , at the point of processing depicted, a replacement gate process has been performed where a dummy gate material is replaced with a workfunction metal layer  118 B at gate electrode regions  120 B,  122 B and  124 B of the logic transistor  104 B. However, in an embodiment, the gate electrode regions  110 B,  112 B and  114 B of the I/O transistor  102 B includes a different workfunction metal layer  119 , even for the same conductivity-type device (i.e., in the case where both the I/O transistor  102 B and the logic transistor  104 B are N-type, or both the I/O transistor  102 B and the logic transistor  104 B are P-type). In an embodiment, the workfunction metal layer  119  has an actual workfunction different than the actual workfunction of the workfunction metal layer  118 B. In one such embodiment, the workfunction metal layer  119  has thickness different than the thickness of the workfunction metal layer  118 B (as shown). In another such embodiment, the workfunction metal layer  119  has a total material composition different than the total material composition of the workfunction metal layer  118 B. In yet another embodiment, the workfunction metal layer  119  differs from the workfunction metal layer  118 B in both thickness and total material composition. In a particular embodiment, the I/O transistor  102 B and the logic transistor  104 B are both N-type devices, and the workfunction metal layer  119  is composed of substantially the same material as the workfunction metal layer  118 B but is thicker than the workfunction metal layer  118 B; the actual workfunction of the workfunction metal layer  119 , as compared with the actual workfunction of the workfunction metal layer  118 B, is shifted towards mid-gap from N-type by an amount approximately in the range of 50-80 mVolts. It is to be understood that additional processing can subsequently be performed to complete the devices of  FIG. 1B , such as gate fill, contact formation, and back-end of line (BEOL) interconnect fabrication. It is also to be understood that, although not depicted, a gate dielectric layer can be disposed between the workfunction metal layers  118 B and  119  and the fins  108 B and  106 B, respectively. 
     In an aspect, a semiconductor fabrication scheme can involve fabrication of different workfunction layers for functionally different devices of like conductivity type. As an example,  FIGS. 2A-2F  illustrate cross-sectional view of various operations in a method of fabricating an I/O transistor and a logic transistor on a common substrate, in accordance with an embodiment of the present invention. 
     Referring to  FIG. 2A , an incomplete portion  200  of a semiconductor structure includes an I/O transistor  202  and a logic transistor  204  disposed on a common substrate  201 . The I/O transistor  202  is formed over a first fin  206 , and the logic transistor  204  is formed over a second fin  208 . In the particular example shown, the I/O transistor  202  has three relatively wider gate electrode regions  210 ,  212  and  214  (cross-sectional view shows the gate length  211  as taken between source/drain regions). The underlying fin  206  can include epitaxial source/drain regions  216 , as shown. Meanwhile, the logic transistor  204  has three relatively narrower gate electrode regions  220 ,  222  and  224  (cross-sectional view shows the gate length  221  as taken between source/drain regions). The underlying fin  208  can also include epitaxial source/drain regions  226 , as is also shown. 
     Referring again to  FIG. 2A , at the point of processing depicted, a replacement gate process has been performed where a dummy gate material is replaced with a workfunction metal layer  218  at gate electrode regions  210 ,  212 ,  214 ,  220 ,  222  and  224 . It is to be understood that, at this stage, the actual workfunction of the workfunction metal layer  218  is the same for the gate electrode regions of both the I/O transistor  202  and the logic transistor  204 . In particular, the workfunction metal layer  218  is formed at the same time, and in the same process operation, for both the I/O transistor  202  and the logic transistor  204 . It is also to be understood that, although not depicted, a gate dielectric layer can be disposed between the workfunction metal layer  218  and the fins  208  and  206 B. Also shown in  FIG. 2A  are gate electrode spacers  228  and interlayer dielectric regions  229 . 
     Referring again to  FIG. 2A , a hardmask layer  230  is formed on portions of the incomplete semiconductor structure  200 . In particular the hardmask layer  230  is formed between the I/O transistor  202  and the logic transistor  204  and, most importantly, within the gate electrode locations  220 ,  222  and  224  of the logic transistor  204 . The hardmask layer  230  is however, not formed in (or is removed from) the gate electrode locations  210 ,  212  and  214  of the I/O transistor  202 , as is depicted. In accordance with an embodiment of the present invention, the hardmask layer is first formed globally, i.e., the hardmask layer  230  is first formed between the I/O transistor  202  and the logic transistor  204 , within the gate electrode locations  220 ,  222  and  224  of the logic transistor  204 , and within the gate electrode locations  210 ,  212  and  214  of the I/O transistor  202 . The portions of the hardmask layer  230  within the gate electrode locations  210 ,  212  and  214  of the I/O transistor  202  is then removed. In one such embodiment, the hardmask layer  230  is first formed globally by a spin-on process. The spin-on layer is then etched selective to other present materials and features to reduce the height of the layer. In an example, the etch rates at different feature locations can vary. As such, in one embodiment, the hardmask layer etches faster from the wider features  210 ,  212  and  214  than from the relatively narrower features  220 ,  222 , and  224 . Accordingly, the spin-on layer may be removed entirely from the wider features  210 ,  212  and  214 , while a portion of the spin-on layer is retained in narrower features  220 ,  222 , and  224 , as depicted. It is to be understood that the portion of the spin-on layer between devices  202  and  204  may be removed rather than retained in the etch process. In an embodiment, the hardmask layer  230  is composed substantially of carbon and is referred to as a carbon hardmask (CHM) layer. 
     Referring to  FIG. 2B , the portion of the workfunction metal layer  218  at gate electrode regions  210 ,  212  and  214  (i.e., at the I/O transistor  202 ) is removed. In an embodiment, the portion of the workfunction metal layer  218  at gate electrode regions  210 ,  212  and  214  is removed selective to the hardmask layer  230 . In one such embodiment, at the logic transistor  204 , upper portions of the workfunction metal layer  218  not protected by the hardmask layer  230  are also removed, as is depicted. Furthermore, if a gate dielectric layer is present on fin  206 , it may be removed at this time, or it may be preserved. In an embodiment, the exposed portions of the workfunction metal layer  218  are removed by a selective etch process such as a wet etch process, dry etch process, or a combination thereof. 
     Referring to  FIG. 2C , a second workfunction metal layer  240  is formed on the structure of  FIG. 2B . More particularly, the second workfunction metal layer  240  is formed in the gate electrode locations  210 ,  212  and  214  of the I/O transistor  202 . Additionally, the second workfunction metal layer  240  can be formed on the exposed portions of the workfunction metal layer  218  and the hardmask layer  230  remaining in the gate electrode locations  220 ,  222  and  224  of the logic transistor, as is depicted in  FIG. 2C . In an embodiment, the second workfunction metal layer  240  has an actual workfunction different than the actual workfunction of the workfunction metal layer  218 . In one such embodiment, the second workfunction metal layer  240  has thickness different than the thickness of the workfunction metal layer  218  (as shown). In another such embodiment, the second workfunction metal layer  240  has a total material composition different than the total material composition of the workfunction metal layer  218 . In yet another embodiment, the second workfunction metal layer  240  differs from the workfunction metal layer  218  in both thickness and total material composition. In a particular embodiment, the I/O transistor  202  and the logic transistor  204  are both N-type devices, and the second workfunction metal layer  240  is composed of substantially the same material as the workfunction metal layer  218  but is thicker than the workfunction metal layer  218 ; the actual workfunction of the second workfunction metal layer  240 , as compared with the actual workfunction of the workfunction metal layer  218 , is shifted towards mid-gap from N-type by an amount approximately in the range of 50-80 mVolts. 
     It is to be understood that, in the case that a gate dielectric layer was removed from the I/O transistor of  FIG. 2B , a gate dielectric layer may be formed immediately prior to the formation of the second workfunction metal layer  240 . Referring again to  FIG. 2C , a second hardmask layer  242  is then formed above the second workfunction metal layer  240 . In one such embodiment, the second hardmask layer  242  is composed of the same material or substantially the same material as hardmask layer  230 . For example, in one such embodiment, the second hardmask layer  242  is a carbon hardmask layer. 
     Referring to  FIG. 2D , the second hardmask layer  242  is etched to recess the portions in the gate electrode regions  210 ,  212  and  214  of the I/O transistor  202 . In the case of the logic transistor  204 , the etching removes the second hardmask layer  242  from the gate electrode regions  220 ,  222  and  224  of the logic transistor  204 . Furthermore, the recessing of the second hardmask layer  242  exposes portions of the second workfunction metal layer  240  at both the I/O transistor  202  and the logic transistor  204 . In an embodiment, the second hardmask layer  242  is recessed by a selective etch process such as an ash process, wet etch process, dry etch process, or a combination thereof. 
     Referring to  FIG. 2E , portions of the second workfunction metal layer  240  exposed upon recessing the second hardmask layer  242  are removed from both the I/O transistor  202  and the logic transistor  204 . In an embodiment, the exposed portions of the second workfunction metal layer  242  are removed by a selective etch process such as a wet etch process, dry etch process, or a combination thereof. 
     Referring to  FIG. 2F , remaining portions of the hardmask layer  230  and the second hardmask layer  242  are removed. The removal exposes the formed and patterned second workfunction metal layer  240  in the gate electrode regions  210 ,  212 , and  214  of the I/O transistor  202  and also exposes the formed and patterned workfunction metal layer  218  in the gate electrode regions  220 ,  222  and  224  of the logic transistor  204 . In an embodiment, the remaining portions of the hardmask layer  230  and the second hardmask layer  242  are removed by a selective etch process such as an ash process, wet etch process, dry etch process, or a combination thereof. Referring again to  FIG. 2F , a dielectric region  230 ′ is shown between the transistors. Although the region  230 ′ may be a region of preserved hardmask, this regions may also be removed and subsequently replaced with an inter-layer dielectric material. It is also to be understood that additional processing can subsequently be performed to complete the devices of  FIG. 2F , such as gate fill, contact formation, and back-end of line (BEOL) interconnect fabrication. 
     In general, referring again to  FIGS. 2A-2F , in an embodiment, the approach described can be used for N-type (e.g., NMOS) or P-type (e.g., PMOS), or both, device fabrication. It is to be understood that the structures resulting from the above exemplary processing scheme, e.g., the structures from  FIG. 2F , may be used in a same or similar form for subsequent processing operations to complete device fabrication, such as PMOS and NMOS device fabrication. As an example of a completed device,  FIGS. 3A and 3B  illustrate a cross-sectional view and a plan view (taken along the a-a′ axis of the cross-sectional view), respectively, of a non-planar semiconductor device such as completed versions of the I/O device  202  or the logic device  204 , in accordance with an embodiment of the present invention. It is to be noted that the cross-sectional view of  FIG. 3A  is taken orthogonal to the cross-sectional view of  FIG. 2F , as taken along any one of the gate lines  210 ,  212 ,  214 ,  220 ,  222  or  224 . Furthermore, in the example, illustrated in  FIGS. 3A and 3B , the gate lines cover three distinct semiconductor fins. 
     Referring to  FIG. 3A , a semiconductor structure or device  300 , such as completed versions of the I/O transistor  202  or the logic transistor  204 , includes a non-planar active region (e.g., a fin structure including a protruding fin portion  304  and a sub-fin region  305 ) formed from a substrate  302 , and within an isolation region  306 . 
     Referring again to  FIG. 3A , a gate line  308  is disposed over the protruding portions  304  of the non-planar active region as well as over a portion of the isolation region  306 . As shown, gate line  308  includes a gate electrode  350  and a gate dielectric layer  352 . In one embodiment, gate line  308  may also include a dielectric cap layer  354 . A gate contact  314 , and overlying gate contact via  316  are also seen from this perspective, along with an overlying metal interconnect  360 , all of which are disposed in inter-layer dielectric stacks or layers  370 . Also seen from the perspective of  FIG. 3A , the gate contact  314  is, in one embodiment, disposed over isolation region  306 , but not over the non-planar active regions. As shown, the fins  304  are considered to be bulk fins since they extend from the underlying substrate  302 . In other embodiments, the fins are formed from a silicon-on insulator (SOI) type substrate and are thus disposed on a global insulator layer. 
     Referring to  FIG. 3B , the gate line  308  is shown as disposed over the protruding fin portions  304 . Source and drain regions  304 A and  304 B of the protruding fin portions  304  can be seen from this perspective. In one embodiment, the source and drain regions  304 A and  304 B are doped portions of original material of the protruding fin portions  304 . In another embodiment, the material of the protruding fin portions  304  is removed and replaced with another semiconductor material, e.g., by epitaxial deposition. In either case, the source and drain regions  304 A and  304 B may extend below the height of dielectric layer  306 , i.e., into the sub-fin region  305 , in the case of bulk type devices. Alternatively, the source and drain regions  304 A and  304 B do not extend below the height of dielectric layer  306 , and are either above or co-planar with the height of dielectric layer  306 . 
     In an embodiment, the semiconductor structure or device  300  is a non-planar device such as, but not limited to, a fin-FET or a tri-gate or similar device. In such an embodiment, a corresponding semiconducting channel region is composed of or is formed in a three-dimensional body. In one such embodiment, the gate electrode stacks of gate lines  308  surround at least a top surface and a pair of sidewalls of the three-dimensional body, as depicted in  FIG. 3A . 
     Substrates  201  and  302  described in association with  FIGS. 2A-2F and 3A , respectively, may be composed of a semiconductor material that can withstand a manufacturing process and in which charge can migrate. In an embodiment, substrate  201  or  302  is a bulk substrate composed of a crystalline silicon, silicon/germanium or germanium layer doped with a charge carrier, such as but not limited to phosphorus, arsenic, boron or a combination thereof. In one embodiment, the concentration of silicon atoms in bulk substrate  201  or  302  is greater than 97%. In another embodiment, bulk substrate  201  or  302  is composed of an epitaxial layer grown atop a distinct crystalline substrate, e.g. a silicon epitaxial layer grown atop a boron-doped bulk silicon mono-crystalline substrate. Bulk substrate  201  or  302  may alternatively be composed of a group III-V material. In an embodiment, bulk substrate  201  or  302  is composed of a III-V material such as, but not limited to, gallium nitride, gallium phosphide, gallium arsenide, indium phosphide, indium antimonide, indium gallium arsenide, aluminum gallium arsenide, indium gallium phosphide, or a combination thereof. In one embodiment, bulk substrate  201  or  302  is composed of a III-V material and the charge-carrier dopant impurity atoms are ones such as, but not limited to, carbon, silicon, germanium, oxygen, sulfur, selenium or tellurium. Alternatively, in place of a bulk substrate, a silicon-on-insulator (SOI) substrate may be used. In such a case, the region  201  depicted in  FIGS. 2A-2F  is a global isolation layer. 
     Isolation region  306  may be composed of a material suitable to ultimately electrically isolate, or contribute to the isolation of, portions of a permanent gate structure from an underlying bulk substrate or isolate active regions formed within an underlying bulk substrate, such as isolating fin active regions. For example, in one embodiment, the isolation region  306  is composed of a dielectric material such as, but not limited to, silicon dioxide, silicon oxy-nitride, silicon nitride, or carbon-doped silicon nitride. 
     Gate line  308  may be composed of a gate electrode stack which includes a gate dielectric layer  352  and a gate electrode layer  350  (such as workfunction metal layer  218  or  240 ). In an embodiment, the gate electrode of the gate electrode stack is composed of a metal gate and the gate dielectric layer is composed of a high-K material. For example, in one embodiment, the gate dielectric layer is composed of a material such as, but not limited to, hafnium oxide, hafnium oxy-nitride, hafnium silicate, lanthanum oxide, zirconium oxide, zirconium silicate, tantalum oxide, barium strontium titanate, barium titanate, strontium titanate, yttrium oxide, aluminum oxide, lead scandium tantalum oxide, lead zinc niobate, or a combination thereof. Furthermore, a portion of gate dielectric layer may include a layer of native oxide formed from the top few layers of the substrate  302 . In an embodiment, the gate dielectric layer is composed of a top high-k portion and a lower portion composed of an oxide of a semiconductor material. In one embodiment, the gate dielectric layer is composed of a top portion of hafnium oxide and a bottom portion of silicon dioxide or silicon oxy-nitride. 
     In one embodiment, the gate electrode layer  350  (such as workfunction metal layer  218  or  240 ) is composed of a metal layer such as, but not limited to, metal nitrides, metal carbides, metal silicides, metal aluminides, hafnium, zirconium, titanium, tantalum, aluminum, ruthenium, palladium, platinum, cobalt, nickel or conductive metal oxides. In a specific embodiment, the gate electrode is composed of a non-workfunction-setting fill material formed above a metal workfunction-setting layer. 
     Spacers associated with the gate electrode stacks (shown as  228  in  FIGS. 2A-2F ) may be composed of a material suitable to ultimately electrically isolate, or contribute to the isolation of, a permanent gate structure from adjacent conductive contacts, such as self-aligned contacts. For example, in one embodiment, the spacers are composed of a dielectric material such as, but not limited to, silicon dioxide, silicon oxy-nitride, silicon nitride, or carbon-doped silicon nitride. 
     Gate contact  314  and overlying gate contact via  316  may be composed of a conductive material. In an embodiment, one or more of the contacts or vias are composed of a metal species. The metal species may be a pure metal, such as tungsten, nickel, or cobalt, or may be an alloy such as a metal-metal alloy or a metal-semiconductor alloy (e.g., such as a silicide material). 
     In an embodiment, the gate line  308  (or lines  210 ,  212 ,  214 ,  220 ,  222  and  224 ) are first formed by poly gate patterning involving poly lithography to define the poly gate by etch of an SiN hardmask and poly subsequently. In one embodiment, a mask is formed on the hardmask layer, the mask composed of a topographic masking portion and an anti-reflective coating (ARC) layer. In a particular such embodiment, the topographic masking portion is a carbon hardmask (CHM) layer and the anti-reflective coating layer is a silicon ARC layer. The topographic masking portion and the ARC layer may be patterned with conventional lithography and etching process techniques. In one embodiment, the mask also includes and uppermost photo-resist layer, as is known in the art, and may be patterned by conventional lithography and development processes. In a particular embodiment, the portions of the photo-resist layer exposed to the light source are removed upon developing the photo-resist layer. Thus, patterned photo-resist layer is composed of a positive photo-resist material. In a specific embodiment, the photo-resist layer is composed of a positive photo-resist material such as, but not limited to, a 248 nm resist, a 193 nm resist, a 157 nm resist, an extreme ultra violet (EUV) resist, an e-beam imprint layer, or a phenolic resin matrix with a diazonaphthoquinone sensitizer. In another particular embodiment, the portions of the photo-resist layer exposed to the light source are retained upon developing the photo-resist layer. Thus, the photo-resist layer is composed of a negative photo-resist material. In a specific embodiment, the photo-resist layer is composed of a negative photo-resist material such as, but not limited to, consisting of poly-cis-isoprene or poly-vinyl-cinnamate. 
     Furthermore, as mentioned briefly in association with  FIG. 2A , the gate stack structure  308  (and gates electrode locations  210 ,  212 ,  214 ,  220 ,  222  and  224 ) may be fabricated by a replacement gate process. In such a scheme, dummy gate material such as polysilicon or silicon nitride pillar material, may be removed and replaced with permanent gate electrode material. In one such embodiment, a permanent gate dielectric layer is also formed in this process, as opposed to being carried through from earlier processing. In an embodiment, dummy gates are removed by a dry etch or wet etch process. In one embodiment, dummy gates are composed of polycrystalline silicon or amorphous silicon and are removed with a dry etch process including use of SF 6 . In another embodiment, dummy gates are composed of polycrystalline silicon or amorphous silicon and are removed with a wet etch process including use of aqueous NH 4 OH or tetramethylammonium hydroxide. In one embodiment, dummy gates are composed of silicon nitride and are removed with a wet etch including aqueous phosphoric acid. 
     In an embodiment, one or more approaches described herein contemplate essentially a dummy and replacement gate process in combination with a dummy and replacement contact process. In one such embodiment, the replacement contact process is performed after the replacement gate process to allow high temperature anneal of at least a portion of the permanent gate stack. For example, in a specific such embodiment, an anneal of at least a portion of the permanent gate structures, e.g., after a gate dielectric layer is formed, is performed at a temperature greater than approximately 600 degrees Celsius. 
     Referring again to  FIG. 3A , the arrangement of semiconductor structure or device  300  places the gate contact over isolation regions. Such an arrangement may be viewed as inefficient use of layout space. In another embodiment, however, a semiconductor device has contact structures that contact portions of a gate electrode formed over an active region. In general, prior to (e.g., in addition to) forming a gate contact structure (such as a via) over an active portion of a gate and in a same layer as a trench contact via, one or more embodiments of the present invention include first using a gate aligned trench contact process. Such a process may be implemented to form trench contact structures for semiconductor structure fabrication, e.g., for integrated circuit fabrication. In an embodiment, a trench contact pattern is formed as aligned to an existing gate pattern. By contrast, conventional approaches typically involve an additional lithography process with tight registration of a lithographic contact pattern to an existing gate pattern in combination with selective contact etches. For example, a conventional process may include patterning of a poly (gate) grid with separate patterning of contact features. 
     It is to be understood that not all aspects of the processes described above need be practiced to fall within the spirit and scope of embodiments of the present invention. For example, in one embodiment, dummy gates need not ever be formed prior to fabricating gate contacts over active portions of the gate stacks. The gate stacks described above may actually be permanent gate stacks as initially formed. Also, the processes described herein may be used to fabricate one or a plurality of semiconductor devices. The semiconductor devices may be transistors or like devices. For example, in an embodiment, the semiconductor devices are a metal-oxide semiconductor field effect transistors (MOS) transistors for logic or memory, or are bipolar transistors. Also, in an embodiment, the semiconductor devices have a three-dimensional architecture, such as a fin-FET device, a trigate device, or an independently accessed double gate device. One or more embodiments may be particularly useful for devices included in a system-on-chip (SoC) product. Additionally, it is to be understood that the processing scheme described in association with  FIGS. 2A-2F  could also be applicable to planar device fabrication. 
     Overall, embodiments described herein provide approaches to fabricate different workfunctions for different devices. One or more embodiments enhances the ability to target the performance of each device independently without the extra cost of additional mask operations. 
       FIG. 4  illustrates a computing device  400  in accordance with one implementation of the invention. The computing device  400  houses a board  402 . The board  402  may include a number of components, including but not limited to a processor  404  and at least one communication chip  406 . The processor  404  is physically and electrically coupled to the board  402 . In some implementations the at least one communication chip  406  is also physically and electrically coupled to the board  402 . In further implementations, the communication chip  406  is part of the processor  404 . 
     Depending on its applications, computing device  400  may include other components that may or may not be physically and electrically coupled to the board  402 . These other components include, but are not limited to, volatile memory (e.g., DRAM), non-volatile memory (e.g., ROM), flash memory, a graphics processor, a digital signal processor, a crypto processor, a chipset, an antenna, a display, a touchscreen display, a touchscreen controller, a battery, an audio codec, a video codec, a power amplifier, a global positioning system (GPS) device, a compass, an accelerometer, a gyroscope, a speaker, a camera, and a mass storage device (such as hard disk drive, compact disk (CD), digital versatile disk (DVD), and so forth). 
     The communication chip  406  enables wireless communications for the transfer of data to and from the computing device  400 . The term “wireless” and its derivatives may be used to describe circuits, devices, systems, methods, techniques, communications channels, etc., that may communicate data through the use of modulated electromagnetic radiation through a non-solid medium. The term does not imply that the associated devices do not contain any wires, although in some embodiments they might not. The communication chip  406  may implement any of a number of wireless standards or protocols, including but not limited to Wi-Fi (IEEE 802.11 family), WiMAX (IEEE 802.16 family), IEEE 802.20, long term evolution (LTE), Ev-DO, HSPA+, HSDPA+, HSUPA+, EDGE, GSM, GPRS, CDMA, TDMA, DECT, Bluetooth, derivatives thereof, as well as any other wireless protocols that are designated as 3G, 4G, 5G, and beyond. The computing device  400  may include a plurality of communication chips  406 . For instance, a first communication chip  406  may be dedicated to shorter range wireless communications such as Wi-Fi and Bluetooth and a second communication chip  406  may be dedicated to longer range wireless communications such as GPS, EDGE, GPRS, CDMA, WiMAX, LTE, Ev-DO, and others. 
     The processor  404  of the computing device  400  includes an integrated circuit die packaged within the processor  404 . In some implementations of embodiments of the invention, the integrated circuit die of the processor includes one or more devices, such as MOS-FET transistors built in accordance with implementations of the invention. The term “processor” may refer to any device or portion of a device that processes electronic data from registers and/or memory to transform that electronic data into other electronic data that may be stored in registers and/or memory. 
     The communication chip  406  also includes an integrated circuit die packaged within the communication chip  406 . In accordance with another implementation of the invention, the integrated circuit die of the communication chip includes one or more devices, such as MOS-FET transistors built in accordance with implementations of the invention. 
     In further implementations, another component housed within the computing device  400  may contain an integrated circuit die that includes one or more devices, such as MOS-FET transistors built in accordance with implementations of embodiments of the invention. 
     In various embodiments, the computing device  400  may be a laptop, a netbook, a notebook, an ultrabook, a smartphone, a tablet, a personal digital assistant (PDA), an ultra mobile PC, a mobile phone, a desktop computer, a server, a printer, a scanner, a monitor, a set-top box, an entertainment control unit, a digital camera, a portable music player, or a digital video recorder. In further implementations, the computing device  400  may be any other electronic device that processes data. 
     Thus, embodiments of the present invention include non-planar I/O and logic semiconductor devices having different workfunctions on common substrates and methods of fabricating non-planar I/O and logic semiconductor devices having different workfunctions on common substrates. 
     In an embodiment, a semiconductor structure includes a first semiconductor device disposed above a substrate. The first semiconductor device has a conductivity type and includes a gate electrode having a first workfunction. The semiconductor structure also includes a second semiconductor device disposed above the substrate. The second semiconductor device has the conductivity type and includes a gate electrode having a second, different, workfunction. 
     In one embodiment, the first semiconductor device is an I/O transistor, and the second semiconductor device is a logic transistor. 
     In one embodiment, the gate electrode having the first workfunction includes a first workfunction metal layer having a thickness, the gate electrode having the second workfunction includes a second workfunction metal layer having a thickness, and the thickness of the first workfunction metal layer is different than the thickness of the second workfunction metal layer. 
     In one embodiment, the gate electrode having the first workfunction includes a first workfunction metal layer having a total material composition, the gate electrode having the second workfunction includes a second workfunction metal layer having a total material composition, and the total material composition of the first workfunction metal layer is different than the total material composition of the second workfunction metal layer. 
     In one embodiment, the gate electrode having the first workfunction includes a first workfunction metal layer having a total material composition and a thickness, the gate electrode having the second workfunction includes a second workfunction metal layer having a total material composition and a thickness, and both the total material composition and the thickness of the first workfunction metal layer are different than the total material composition and the thickness of the second workfunction metal layer. 
     In one embodiment, the conductivity type is N-type. 
     In one embodiment, the gate electrode having the first workfunction includes a first workfunction metal layer having a thickness, the gate electrode having the second workfunction includes a second workfunction metal layer having a thickness. The thickness of the first workfunction metal layer is greater than the thickness of the second workfunction metal layer, and the first workfunction is closer to mid-gap than the second workfunction by an amount approximately in the range of 50-80 mVolts. 
     In one embodiment, the gate electrode of the first semiconductor device has a gate length different than a gate length of the gate electrode of the second semiconductor device. 
     In one embodiment, both the first and second semiconductor devices are fin-FET or tri-gate devices. 
     In an embodiment, a system-on-chip (SoC) integrated circuit includes an N-type I/O transistor disposed above a substrate, the N-type I/O transistor including a gate electrode having a first workfunction and a first gate length. An N-type logic transistor is disposed above the substrate, the N-type logic transistor including a gate electrode having a second, lower, workfunction and having a second gate length less than the first gate length. 
     In one embodiment, the gate electrode having the first workfunction includes a first workfunction metal layer having a thickness, the gate electrode having the second workfunction includes a second workfunction metal layer having a thickness, and the thickness of the first workfunction metal layer is greater than the thickness of the second workfunction metal layer. 
     In one embodiment, the gate electrode having the first workfunction includes a first workfunction metal layer having a total material composition, the gate electrode having the second workfunction includes a second workfunction metal layer having a total material composition, and the total material composition of the first workfunction metal layer is different than the total material composition of the second workfunction metal layer. 
     In one embodiment, the gate electrode having the first workfunction includes a first workfunction metal layer having a total material composition and a thickness, the gate electrode having the second workfunction includes a second workfunction metal layer having a total material composition and a thickness, and both the total material composition and the thickness of the first workfunction metal layer are different than the total material composition and the thickness of the second workfunction metal layer. 
     In one embodiment, the first workfunction is closer to mid-gap than the second workfunction by an amount approximately in the range of 50-80 mVolts. 
     In one embodiment, both the first and second semiconductor devices are fin-FET or tri-gate devices. 
     In an embodiment, a method of fabricating a semiconductor structure involves forming a first semiconductor fin and a second semiconductor fin above a substrate. The method also involves forming a first plurality of gate lines having a first pitch over the first semiconductor fin and forming a second plurality of gate lines having a second, narrower, pitch over the second semiconductor fin, both of the first and second pluralities of gate lines including a first workfunction metal layer of a conductivity type. The method also involves replacing the first workfunction metal layer of the conductivity type with a second workfunction metal layer of the conductivity type in the first plurality of gate lines but not in the second plurality of gate lines. 
     In one embodiment, forming the first plurality of gate lines and the second plurality of gate lines involves using a replacement gate technique. 
     In one embodiment, replacing the first workfunction metal layer of the conductivity type with the second workfunction metal layer of the conductivity type involves masking a portion of the first workfunction metal layer of the conductivity type in the second plurality of gate lines, but not in the first plurality of gate lines. 
     In one embodiment, masking the portion of the first workfunction metal layer of the conductivity type in the second plurality of gate lines involves forming and etching a carbon hardmask. The etch rate of the carbon hardmask in the second plurality of gate lines is slower than the etch rate of the carbon hardmask in the first plurality of gate lines. 
     In one embodiment, replacing the first workfunction metal layer of the conductivity type with the second workfunction metal layer of the conductivity type involves etching the first workfunction metal layer of the conductivity type and forming the second workfunction metal layer of the conductivity type with a thickness greater than a thickness of the first workfunction metal layer of the conductivity type. 
     In one embodiment, the method further involves forming an I/O transistor from the first semiconductor fin and the first plurality of gate lines. The method also involves forming a logic transistor from the second semiconductor fin and the second plurality of gate lines. 
     In one embodiment, forming the I/O transistor involves forming an N-type I/O transistor, and forming the logic transistor involves forming an N-type logic transistor.