Abstract: A gate structure in a semiconductor device includes: a gate stack formed on a substrate with three sections: a bottom portion, a top portion, and a sacrificial cap layer over the top portion; gate spacers; source and drain regions; a nitride encapsulation over top and sidewalls of the gate stack after removal of the sacrificial cap layer; an organic planarizing layer over the nitride encapsulation, planarizing the encapsulation; and silicidation performed over the source and drain regions and the bottom portion after removal of the nitride encapsulation, the organic planarizing layer, and the top portion of the gate stack.

Abstract: A method of manufacturing a transistor by which sufficient stress can be applied to a channel region within allowable ranges of concentrations of Ge and C in a mixed crystal layer. A semiconductor device is also provided.

Abstract: Systems and methods are provided for fabricating a semiconductor device structure. An example semiconductor device structure includes a channel layer formed of a Germanium compound having a Germanium concentration B formed on a semiconductor substrate having a Germanium concentration of A, the Germanium concentration of the substrate A being less than the Germanium concentration of the channel layer B. The structure further includes a capping layer formed to separate the channel layer from a metal gate, the capping layer having a Germanium concentration of C, the Germanium concentration of the channel layer B being greater than the Germanium concentration of the capping layer C.

Abstract: The present invention provides a MOS transistor, including a substrate, a gate oxide, a gate, a source/drain region and a silicide layer. The gate oxide is disposed on the substrate and the gate is disposed on the gate oxide. The source/drain region is disposed in the substrate at two sides of the gate. The silicide layer is disposed on the source/drain region, wherein the silicide layer includes a curved bottom surface and a curved top surface, both the curved top surface and the curved bottom surface bend toward the substrate and the curved top surface is sunken from two sides thereof, two ends of the silicide layer point tips raised up over the source/drain region and the silicide layer in the middle is thicker than the silicide layer in the peripheral, thereby forming a crescent structure. The present invention further provides a manufacturing method of the MOS transistor.

Abstract: One or more embodiments of techniques or systems for forming a semiconductor structure are provided herein. In some embodiments, a semiconductor structure includes a substrate, a first lightly doped drain (LDD), a second LDD, an interface layer (IL), a high-k stack, a gate region, a dummy poly region, a first hard mask (HM) region, a second HM region, and a seal spacer region. The HK stack has a HK stack width and the gate region has a gate region width that is less than or substantially equal to the HK stack width. Because of the increased width of the HK stack, some of the HK stack likely overlaps some of the first LDD or the second LDD. In this manner, a saturation current and a threshold voltage associated with the semiconductor structure are improved. The increased width of the HK stack also protects more of the IL during LDD implanting.

Abstract: A gate structure is provided on a channel portion of a semiconductor substrate. The gate structure may include an electrically conducting layer present on a gate dielectric layer, a semiconductor-containing layer present on the electrically conducting layer, a metal semiconductor alloy layer present on the semiconductor-containing layer, and a dielectric capping layer overlaying the metal semiconductor alloy layer. In some embodiments, carbon and/or nitrogen can be present within the semiconductor-containing layer, the metal semiconductor alloy layer or both the semiconductor-containing layer and the metal semiconductor alloy layer. The presence of carbon and/or nitrogen within the semiconductor-containing layer and/or the metal semiconductor alloy layer provides stability to the gate structure. In another embodiment, a layer of carbon and/or nitrogen can be formed between the semiconductor-containing layer and the metal semiconductor alloy layer.

Abstract: Embodiments of the present invention provide an improved structure and method for forming high aspect ratio contacts. A horizontally formed contact etch stop layer is deposited in a narrow area where a contact is to be formed. A gas cluster ion beam (GCIB) process is used in the deposition of the horizontally formed contact etch stop layer.

Abstract: A field device and method of operating high voltage semiconductor device applied with the same are provided. The field device includes a first well having a second conductive type and second well having a first conductive type both formed in the substrate (having the first conductive type) and extending down from a surface of the substrate, the second well adjacent to one side of the first well and the substrate is at the other side of the first well; a first doping region having the first conductive type and formed in the second well, the first doping region spaced apart from the first well; a conductive line electrically connected to the first doping region and across the first well region; and a conductive body insulatively positioned between the conductive line and the first well, and the conductive body correspondingly across the first well region.

Abstract: The embodiments of mechanisms for doping lightly doped drain (LDD) regions by driving dopants from highly doped source and drain regions by annealing for finFET devices are provided. The mechanisms overcome the limitation by shadowing effects of ion implantation for advanced finFET devices. The highly doped source and drain regions are formed by epitaxial growing one or more doped silicon-containing materials from recesses formed in the fins. The dopants are then driven into the LDD regions by advanced annealing process, which can achieve targeted dopant levels and profiles in the LDD regions.

Abstract: A method of forming a semiconductor device is provided. At least one gate structure including a dummy gate is formed on a substrate. A contact etch stop layer and a dielectric layer are formed to cover the gate structure. A portion of the contact etch stop layer and a portion of the dielectric layer are removed to expose the top of the gate structure. A dry etching process is performed to remove a portion of the dummy gate of the gate structure. A hydrogenation treatment is performed to the surface of the remaining dummy gate. A wet etching process is performed to remove the remaining dummy gate and thereby form a gate trench.

Abstract: A portion of a top semiconductor layer of a semiconductor-on-insulator (SOI) substrate is patterned into a semiconductor fin having substantially vertical sidewalls. A portion of a body region of the semiconductor fin is exposed on a top surface of the semiconductor fin between two source regions having a doping of a conductivity type opposite to the body region of the semiconductor fin. A metal semiconductor alloy portion is formed directly on the two source regions and the top surface of the exposed body region between the two source regions. The doping concentration of the exposed top portion of the body region may be increased by ion implantation to provide a low-resistance contact to the body region, or a recombination region having a high-density of crystalline defects may be formed. A hybrid surface semiconductor-on-insulator (HSSOI) metal-oxide-semiconductor-field-effect-transistor (MOSFET) thus formed has a body region that is electrically tied to the source region.

Abstract: The present invention discloses a method for manufacturing a semiconductor device, comprising the steps of: forming a dummy gate stack structure on a substrate, wherein the dummy gate stack structure contains carbon-based materials; forming source/drain region in the substrate on both sides of the dummy gate stack structure; performing etching to remove the dummy gate stack structure until the substrate is exposed, resulting in a gate trench; and forming a gate stack structure in the gate trench. In accordance with the method for manufacturing a semiconductor device of the present invention, the dummy gate made of carbon-based materials is used to substitute the dummy gate made of silicon-based materials, then no oxide liner and/or etch blocking layer needs be added while the dummy gate is removed by etching in the gate last process, thus the reliability of device is ensured while the process is simplified and the cost is reduced.

Abstract: A method for fabricating a semiconductor device is provided, which includes forming a screen layer on a substrate, the screen layer including a first portion doped with a first type impurity, forming a first undoped semiconductor layer on the screen layer, forming a gate structure on the first semiconductor layer, forming a first amorphous region on both sides of the gate structure in the first semiconductor layer, and re-crystallizing the first amorphous region through performing a first heat treatment of the first amorphous region.

Abstract: Embodiments of the present invention generally relate to methods of forming epitaxial layers and devices having epitaxial layers. The methods generally include forming a first epitaxial layer including phosphorus and carbon on a substrate, and then forming a second epitaxial layer including phosphorus and carbon on the first epitaxial layer. The second epitaxial layer has a lower phosphorus concentration than the first epitaxial layer, which allows for selective etching of the second epitaxial layer and undesired amorphous silicon or polysilicon deposited during the depositions. The substrate is then exposed to an etchant to remove the second epitaxial layer and undesired amorphous silicon or polysilicon. The carbon present in the first and second epitaxial layers reduces phosphorus diffusion, which allows for higher phosphorus doping concentrations. The increased phosphorus concentrations reduce the resistivity of the final device.

Abstract: A semiconductor device and its manufacturing method are disclosed. The semiconductor device comprises a gate, and source and drain regions on opposite sides of the gate, wherein a portion of a gate dielectric layer located above the channel region is thinner than a portion of the gate dielectric layer located at the overlap region of the drain and the gate. The thicker first thickness portion may ensure that the device can endure a higher voltage at the drain to gate region, while the thinner second thickness portion may ensure excellent performance of the device.

Abstract: A semiconductor structure includes a first gate and a second gate, a first spacer and a second spacer, two first epitaxial structures and two second epitaxial structures. The first gate and the second gate are located on a substrate. The first spacer and the second spacer are respectively located on the substrate beside the first gate and the second gate. The first epitaxial structures and the second epitaxial structures are respectively located in the substrate beside the first spacer and the second spacer, wherein the first spacer and the second spacer have different thicknesses, and the spacing between the first epitaxial structures is different from the spacing between the second epitaxial structures. Moreover, the present invention also provides a semiconductor process forming said semiconductor structure.

Abstract: A self-align method of preparing semiconductor gates for formation of a silicide, such as a cobalt silicide (CoSi) layer, is disclosed. Deposition of silicon nitride (SiN) and low-temperature oxide (LTO) liner types, the SiN liner having an overhang structure, prevent damage to the gates while forming a self-aligned source. The undamaged gates are suitable for CoSi deposition.

Abstract: A method includes forming a first gate stack and a second gate stack over a first portion and a second portion, respectively, of a semiconductor substrate, masking the first portion of the semiconductor substrate, and with the first portion of the semiconductor substrate being masked, implanting the second portion of the semiconductor substrate with an etch-tuning element. The first portion and the second portion of the semiconductor substrate are etched simultaneously to form a first opening and a second opening, respectively, in the semiconductor substrate. The method further includes epitaxially growing a first semiconductor region in the first opening, and epitaxially growing a second semiconductor region in the second opening.

Abstract: A method of forming a metal silicide layer includes the following steps. At first, at least a gate structure, at least a source/drain region and a first dielectric layer are formed on a substrate, and the gate structure is aligned with the first dielectric layer. Subsequently, a cap layer covering the gate structure is formed, and the cap layer does not overlap the first dielectric layer and the source/drain region. Afterwards, the first dielectric layer is removed to expose the source/drain region, and a metal silicide layer totally covering the source/drain region is formed.

Abstract: A method includes forming a stressed Si layer in a trench formed in a stress layer deposited on a substrate. The stressed Si layer forms an active channel region of a device. The method further includes forming a gate structure in the active channel region formed from the stressed Si layer.

Abstract: An integrated circuit device and method for manufacturing the integrated circuit device are disclosed. In an example, the method includes forming a gate structure over a substrate; forming a doped region in the substrate; performing a first etching process to remove the doped region and form a trench in the substrate; and performing a second etching process that modifies the trench by removing portions of the substrate.

Abstract: Erbium silicide layers can be used in CMOS transistors in which the work function of the erbium silicide layers can be tuned for use in PMOS and NMOS devices. A nano-laminate sputtering approach can be used in which silicon and erbium layers are alternatingly deposited to determine optimum layer properties, composition profiles, and erbium to silicon ratios for a particular gate stack.

Abstract: Semiconductor devices and methods of forming semiconductor devices are provided herein. In an embodiment, a semiconductor device includes a semiconductor substrate. A source region and a drain region are disposed in the semiconductor substrate. A channel region is defined in the semiconductor substrate between the source region and the drain region. A gate dielectric layer overlies the channel region of the semiconductor substrate, and a gate electrode overlies the gate dielectric layer. The channel region includes a first carbon-containing layer, a doped layer overlying the first carbon-containing layer, a second carbon-containing layer overlying the doped layer, and an intrinsic semiconductor layer overlying the second carbon-containing layer. The doped layer includes a dopant that is different than carbon.

Abstract: A method of fabrication a transistor device with a non-uniform stress layer including the following processes. First, a semiconductor substrate having a first transistor region is provided. A low temperature deposition process is carried out to form a first tensile stress layer on a transistor within the first transistor region, wherein a temperature of the low temperature deposition process is lower than 300 degree Celsius (° C.) . Then, a high temperature annealing process is performed, wherein a temperature of the high temperature annealing process is at least 150° C. higher than a temperature of the low temperature deposition process. Finally, a second tensile stress layer is formed on the first tensile stress layer, wherein the first tensile stress layer has a tensile stress lower than a tensile stress of the second tensile stress layer.

Abstract: A carbon-based semiconductor structure includes a substrate and a gate stack. The gate stack includes a carbon-based gate electrode formed on the substrate. The gate stack also includes a gate dielectric formed on the carbon-based gate electrode. The gate stack further includes a carbon-based channel formed on the gate dielectric.

Abstract: The present disclosure provides a method for making an integrated circuit in one embodiment. The method includes providing a semiconductor substrate having an active region and a first gate stack disposed on the semiconductor substrate in the active region; forming in-situ phosphorous-doped silicon carbide (SiCP) features on the semiconductor substrate and disposed on sides of the first gate stack; replacing the first gate stack with a second gate stack having a high k dielectric material layer; and thereafter performing a millisecond annealing (MSA) process with a thermal profile having a first thermal wavelet and a second thermal wavelet.

Abstract: The present invention relates to a method for manufacturing a heterojunction semiconductor device including an AlGaN layer, the method including the steps of (a) forming a dummy electrode in a region where a gate electrode is arranged on the AlGaN layer, (b) depositing a dielectric film on the AlGaN layer by exposing side surfaces of the dummy electrode, using a device having anisotropy, (c) forming an opening in the dielectric film by removing the dummy electrode, and (d) forming the gate electrode that extends from inside the opening onto the dielectric film in a vicinity of the opening.

Abstract: Provided are methods of forming field effect transistors. The method includes preparing a substrate with a first region and a second region, forming fin portions on the first and second regions, each of the fin portions protruding from the substrate and having a first width, forming a first mask pattern to expose the fin portions on the first region and cover the fin portions on the second region, and changing widths of the fin portions provided on the first region.

Abstract: The present description relates to the field of fabricating microelectronic devices having non-planar transistors. Embodiments of the present description relate to the formation of source/drain contacts within non-planar transistors, wherein a titanium-containing contact interface may be used in the formation of the source/drain contact with a discreet titanium silicide formed between the titanium-containing interface and a silicon-containing source/drain structure.

Abstract: A method of trimming spacers includes etching a silicon oxide spacer when forming an outmost spacer, so that a silicon carbon nitride spacer contacting the gate electrode exposes an area. The exposure area of the silicon carbon nitride spacer can then be partly removed by phosphate acid. At the end of the semiconductor process, at least part of the top surface of the silicon carbon nitride spacer will be lower than the top surface of a gate electrode.

Abstract: A disposable gate structure straddling a semiconductor fin is formed. A source region and a drain region are formed employing the disposable gate structure as an implantation mask. A planarization dielectric layer is formed such that a top surface of the planarization dielectric layer is coplanar with the disposable gate structure. A gate cavity is formed by removing the disposable gate structure. An epitaxial cap layer is deposited on physically exposed semiconductor surfaces of the semiconductor fin by selective epitaxy. A gate dielectric layer is formed on the epitaxial cap layer, and a gate electrode can be formed by filling the gate cavity. The epitaxial cap layer can include a material that reduces the density of interfacial defects at an interface with the gate dielectric layer.

Abstract: A semiconductor device comprising a substrate having a transistor that includes a metal gate structure; a first oxide layer formed over the substrate; a silane layer formed on the first oxide layer; and a non-conductive metal oxide layer grown on the metal gate structure, wherein the silane layer inhibits nucleation and growth of the non-conductive metal oxide layer.

Abstract: A method for forming semiconductor devices using damascene techniques provides self-aligned conductive lines that have an end-to-end spacing less than 60 nm without shorting. The method includes using at least one sacrificial hardmask layer to produce a mandrel and forming a void in the mandrel. The sacrificial hardmask layers are formed over a base material which is advantageously an insulating material. Another hardmask layer is also disposed over the base material and under the mandrel in some embodiments. Spacer material is formed alongside the mandrel and filling the void. The spacer material serves as a mask and at least one etching procedure is carried out to translate the pattern of the spacer material into the base material. The patterned base material includes trenches and raised portions. Conductive features are formed in the trenches using damascene techniques.

Abstract: A method of forming metal silicide-comprising material includes forming a substrate which includes a first stack having second metal over first metal over silicon and a second stack having second metal over silicon. The first and second metals are of different compositions. The substrate is subjected to conditions which react the second metal with the silicon in the second stack to form metal silicide-comprising material from the second stack. The first metal between the second metal and the silicon in the first stack precludes formation of a silicide comprising the second metal and silicon from the first stack. After forming the metal silicide-comprising material, the first metal, the second metal and the metal silicide-comprising material are subjected to an etching chemistry that etches at least some remaining of the first and second metals from the substrate selectively relative to the metal silicide-comprising material.

Abstract: A method for forming a trench includes etching an oxide layer to form a trench therein, conformally forming a first reaction layer along a surface of the trench, the first reaction layer including a first region on an upper portion of the trench and a second region on a lower portion of the trench, forming a barrier layer by reacting a first amount of etching gas with the first region of the first reaction layer, and etching the oxide layer on a lower portion of the second region by reacting a second amount of etching gas with the second region of the first reaction layer, the second amount of etching gas being greater than the first amount of etching gas.

Abstract: A method for manufacturing a semiconductor device comprises growing a source/drain epitaxy region over a plurality of gates on a substrate, wherein a top surface of the source/drain epitaxy region is at a height above a top surface of each of the plurality of gates, forming at least one opening in the source/drain epitaxy region over a top surface of at least one gate, forming a silicide layer on the source/drain epitaxy region, wherein the silicide layer lines lateral sides of the at least one opening, depositing a dielectric layer on the silicide layer, wherein the dielectric layer is deposited in the at least one opening between the silicide layer on lateral sides of the at least one opening, etching the dielectric layer to form a contact area, and depositing a conductor in the contact area.

Abstract: Embodiments of present invention provide a method of forming a semiconductor device. The method includes depositing a layer of metal over one or more channel regions of respective one or more transistors in a substrate, the layer of metal having a first region and a second region; lowering height of the first region of the layer of metal; forming an insulating layer over the first region of lowered height, the insulating layer being formed to have a top surface coplanar with the second region of the layer of metal; and forming at least one contact to a source/drain region of the one or more transistors. Structure of the semiconductor device formed thereby is also provided.

Abstract: Gate to contact shorts are reduced by forming dielectric caps in replaced gate structures. Embodiments include forming a replaced gate structure on a substrate, the replaced gate structure including an ILD having a cavity, a first metal on a top surface of the ILD and lining the cavity, and a second metal on the first metal and filling the cavity, planarizing the first and second metals, forming an oxide on the second metal, removing the oxide, recessing the first and second metals in the cavity, forming a recess, and filling the recess with a dielectric material. Embodiments further include dielectric caps having vertical sidewalls, a trapezoidal shape, a T-shape, or a Y-shape.

Abstract: A semiconductor device with improved roll-off resistivity and reliability are provided. The semiconductor device includes a gate dielectric overlying a semiconductor substrate, a gate electrode overlying the gate dielectric, a gate silicide region on the gate electrode, a source/drain region adjacent the gate dielectric, and a source/drain silicide region on the source/drain region, wherein the source/drain silicide region and the gate silicide region have different metal compositions.

Abstract: A semiconductor device is provided that includes a gate structure on a channel region of a substrate. A source region and a drain region are present on opposing sides of the channel region. A first metal semiconductor alloy is present on an upper surface of at least one of the source and drain regions. The first metal semiconductor alloy extends to a sidewall of the gate structure. A dielectric layer is present over the gate structure and the first metal semiconductor alloy. An opening is present through the dielectric layer to a portion of the first metal semiconductor alloy that is separated from the gate structure. A second metal semiconductor alloy is present in the opening, is in direct contact with the first metal semiconductor alloy, and has an upper surface that is vertically offset and is located above the upper surface of the first metal semiconductor alloy.

Abstract: This disclosure relates to a semiconductor device and a manufacturing method thereof. The semiconductor device comprises: a patterned stacked structure formed on a semiconductor substrate, the stacked structure comprising a silicon-containing semiconductor layer overlaying the semiconductor substrate, a gate dielectric layer overlaying the silicon-containing semiconductor layer and a gate layer overlaying the gate dielectric layer; and a doped epitaxial semiconductor layer on opposing sides of the silicon-containing semiconductor layer forming raised source/drain extension regions. Optionally, the silicon-containing semiconductor layer may be used as a channel region. According to this disclosure, the source/drain extension regions can be advantageously made to have a shallow junction depth (or a small thickness) and a high doping concentration.

Abstract: An example embodiment relates to a semiconductor device including a semiconductor element. The semiconductor element may include a plurality of unit layers spaced apart from each other in a vertical direction. Each unit layer may include a patterned graphene layer. The patterned graphene layer may be a layer patterned in a nanoscale. The patterned graphene layer may have a nanomesh or nanoribbon structure. The semiconductor device may be a transistor or a diode. An example embodiment relates to a method of making a semiconductor device including a semiconductor element.

Abstract: A method for manufacturing a semiconductor device includes providing a substrate, forming a pseudo-gate stack and sidewalls on the substrate, forming an S/D region on both sides of the pseudo-gate stack, and forming a stop layer and a first interlayer dielectric layer covering the entire semiconductor device; removing part of the stop layer to expose the pseudo-gate stack, and further removing the pseudo-gate stack to expose the channel region; etching the channel region to form a groove structure; forming a new channel region to flush with the upper surface of the substrate, wherein the new channel region includes a buffer layer, a Ge layer, and a Si cap layer; forming a gate stack. Accordingly, the present application also discloses a semiconductor device. The present application can effectively improve the carrier mobility and the performance of the semiconductor device by replacing Si with Ge to form a new channel region.

Abstract: Embodiments of the present disclosure include a method for forming a semiconductor device, a method for forming a MISFET device, and a MISFET device. An embodiment is a method for forming a semiconductor device, the method including forming a source/drain over a substrate, forming a first etch stop layer on the source/drain, and forming a gate dielectric layer on the first etch stop layer and along the substrate. The method further includes forming a gate electrode on the gate dielectric layer, forming a second etch stop layer on the gate electrode, and removing the gate dielectric layer from over the source/drain.

Abstract: A semiconductor transistor is formed as follows. A gate electrode is formed over but is insulated from a semiconductor body region. A first layer of insulating material is formed over the gate electrode and the semiconductor body region. A second layer of insulating material different from the first layer of insulating material is formed over the first layer of insulating material. Only the second layer of insulating material is etched to form spacers along the side-walls of the gate electrode. Impurities are implanted through the first layer of insulating material to form a source region and a drain region in the body region. A substantial portion of those portions of the first layer of insulting material extending over the source and drain regions is removed.

Abstract: A junctionless accumulation-mode (JAM) semiconductive device is isolated from a semiconductive substrate by a reverse-bias band below a prominent feature of a JAM semiconductive body. Processes of making the JAM device include implantation and epitaxy.

Abstract: A method is provided for fabricating a PMOS transistor. The method includes providing a semiconductor substrate; and forming gate structures on a surface of the semiconductor substrate. The method also includes forming sidewall spacers around the gate structures; and forming a protection layer on the sidewall spacers. Further, the method includes forming sigma shape trenches in the semiconductor substrate at sides of the gate structures; and forming SiGe structures with a surface protruding from the surface of the semiconductor substrate in the sigma shape trenches. Further, the method also includes removing the sidewall spacers and a portion of the protection layer; and forming lightly doped drain regions in the semiconductor substrate at both sides of the gate structures.

Abstract: Embodiments of the invention provide approaches for forming gate and source/drain (S/D) contacts. Specifically, the semiconductor device includes a gate transistor formed over a substrate, a S/D contact formed over a trench-silicide (TS) layer and positioned adjacent the gate transistor, and a gate contact formed over the gate transistor, wherein at least a portion of the gate contact is aligned over the TS layer. This structure enables contact with the TS layer, thereby decreasing the distance between the gate contact and the source/drain, which is desirable for ultra-area-scaling.

Abstract: A tunneling device may include a tunnel barrier layer, a first material layer including a first conductivity type two-dimensional material on a first surface of the tunnel barrier layer and a second material layer including a second conductivity type two-dimensional material on a second surface of the tunnel barrier layer. The tunneling device may use a tunneling current through the tunnel barrier layer between the first material layer and the second material layer.

Abstract: A method for manufacturing a PMOSFET including defining an active region for the PMOSFET on a semiconductor substrate; forming an interfacial oxide layer on a surface of the substrate; forming a high-K gate dielectric layer on the interfacial oxide layer; forming a metal gate layer on the dielectric layer; implanting dopant ions into the metal gate layer; forming a Poly-Si layer on the metal gate layer; patterning the Poly-Si layer, the metal gate layer, the dielectric layer and the interfacial oxide layer to form a gate stack; forming a gate spacer surrounding the gate stack; and forming S/D regions. During annealing to form the S/D regions, dopant ions implanted in the metal gate layer may accumulate at upper and bottom interfaces of the dielectric, and electric dipoles with appropriate polarities are generated by interface reaction at the bottom interface, so that the metal gate has its effective work function adjusted.