Abstract: The present disclosure relates to a transistor device having a strained source/drain region. In some embodiments, the transistor device has a gate structure arranged over a semiconductor substrate. The transistor device also has a strained source/drain region arranged within the semiconductor substrate along a side of the gate structure. The strained source/drain region includes a first layer and a second layer over the first layer. The first layer has a strain inducing component with a first concentration profile that decreases as a distance from the second layer decreases, and the second layer has the strain inducing component with a second non-zero concentration profile that is discontinuous with the first concentration profile.

Abstract: Methods comprising forming a cobalt formation on an active feature of a semiconductor device, wherein the semiconductor device comprises an inactive feature above the cobalt formation; forming a cap on the cobalt formation; removing at least a portion of the inactive feature, wherein the cobalt formation is substantially not removed; forming a dielectric material above the cap; and forming a first contact to the cobalt formation. Systems configured to implement the methods. Semiconductor devices produced by the methods.

Abstract: An embodiment is a semiconductor structure. The semiconductor structure includes a fin on a substrate. A gate structure is over the fin. A source/drain is in the fin proximate the gate structure. The source/drain includes a bottom layer, a supportive layer over the bottom layer, and a top layer over the supportive layer. The supportive layer has a different property than the bottom layer and the top layer, such as a different material, a different natural lattice constant, a different dopant concentration, and/or a different alloy percent content.

Abstract: A semiconductor device includes a base substrate; a plurality of doped regions formed in the base substrate; and a target capping layer formed on surfaces of the doped regions. The target capping layer includes a silicide region and a non-silicide region surrounding the silicide region, and the silicide region has a reduced thickness compared with a thickness of the non-silicide region. The semiconductor device further includes a metal silicide layer formed in the silicide region of the target capping layer and having the reduced thickness; a dielectric layer formed on the target capping layer and the base substrate; and a plurality of vias formed in the dielectric layer and connected to the metal silicide layer.

Abstract: An apparatus includes at least one first device having a first contacted poly pitch (CPP) and a first contact. The first contact has a first contact size. The apparatus also includes at least one second device having a second CPP, a second contact, and a contact liner. The second CPP is larger than the first CPP. The second contact size is constrained by the contact liner, such that the contact liner reduces a contact opening for the second contact.

Abstract: The disclosed technology generally relates to semiconductor devices, and more specifically to electrical contacts to a transistor device, and a method of making such electrical contacts. In one aspect, a method of forming one or more self-aligned gate contacts in a semiconductor device includes providing a substrate having formed thereon at least one gate stack, where the gate stack includes a gate dielectric and a gate electrode formed over an active region in or on the substrate, and where the substrate further has formed thereon a spacer material coating lateral sides of the at least one gate stack. The method additionally includes selectively recessing the gate electrode of the at least one gate stack against the spacer material, thereby creating a first set of recess cavities. The method additionally includes filling the first set of recess cavities with a dielectric material gate cap.

Abstract: Structures and static random access memory bit cells including complementary field effect transistors and methods of forming such structures and bit cells. A buried cross-couple interconnect is arranged in a vertical direction beneath a first field-effect transistor and a second field-effect transistor. The buried cross-couple interconnect is coupled with a gate electrode of the first field-effect transistor, and the buried cross-couple interconnect is also coupled with a source/drain region of the second field-effect transistor.

Abstract: A fin field effect transistor (FinFET) device structure and method for forming FinFET device structure are provided. The FinFET structure includes a substrate and an isolation structure formed on the substrate. The FinFET structure also includes a fin structure extending above the substrate, and the fin structure is embedded in the isolation structure. The FinFET structure further includes an epitaxial structure formed on the fin structure, the epitaxial structure has a pentagon-like shape, and an interface between the epitaxial structure and the fin structure is lower than a top surface of the isolation structure.

Abstract: There is provided a semiconductor device comprising: a semiconductor substrate; an emitter region of a first conductivity type provided inside the semiconductor substrate; a base region of a second conductivity type provided below the emitter region inside the semiconductor substrate; an accumulation region of the first conductivity type provided below the base region inside the semiconductor substrate, and containing hydrogen as an impurity; and a trench portion provided to pass through the emitter region, the base region and the accumulation region from an upper surface of the semiconductor substrate.

Abstract: A semiconductor structure is disclosed including a semiconductor substrate having two or more fins. The semiconductor structure includes a recessed gate structure having opposing sidewalls located over one of the fins. The semiconductor structure includes a gate spacer disposed on the opposing sidewalls of the recessed gate structure. The semiconductor structure includes a source/drain region disposed between adjacent gate spacers. The semiconductor structure includes a first conductive material disposed on the source/drain region and an interlevel dielectric layer disposed on a top surface of the semiconductor structure defining an opening therein to an exposed top surface of the first conductive material. A width of an upper portion of the opening is greater than the width of the lower portion of the opening. The lower portion of opening is aligned with the first conductive material. The semiconductor structure includes a second conductive material disposed in the opening.

Abstract: First and second p-type semiconductor regions (electric-field relaxation layers) are formed by ion implantation using a dummy gate and side wall films on both sides of the dummy gate as a mask. In this manner, it is possible to reduce a distance between the first p-type semiconductor region and a trench and a distance between the second p-type semiconductor region and the trench, and symmetry of the first and second p-type semiconductor regions with respect to the trench can be enhanced. As a result, semiconductor elements can be miniaturized, and on-resistance and an electric-field relaxation effect, which are in a trade-off relationship, can be balanced, so that characteristics of the semiconductor elements can be improved.

Abstract: Techniques for reducing work function metal variability along the channel of VFET devices are provided. In one aspect, a method of forming a VTFET device includes: patterning fins in a wafer; forming bottom source/drains at a base of the fins and bottom spacers on the bottom source/drains; forming gate stacks over the fins including a gate conductor having a combination of work function metals including an outer layer and at least one inner layer of the work function metals; isotropically etching the work function metals which recesses the gate stacks with an outwardly downward sloping profile; isotropically etching the at least one inner layer while covering the outer layer of the work function metals to eliminate the outwardly downward sloping profile of the gate stacks; forming top spacers above the gate stacks; and forming top source and drains at tops of the fins. A VTFET device is also provided.

Abstract: Semiconductor devices and methods are provided. A method according to the present disclosure includes receiving a substrate that includes a first semiconductor layer, a second semiconductor layer, and a third semiconductor layer; forming a plurality of fins over the third semiconductor layer; forming a trench between two of the plurality of fins; depositing a dummy material in the trench; forming a gate structure over channel regions of the plurality of the fins; forming source/drain features over source/drain regions of the plurality of the fins; bonding the substrate on a carrier wafer; removing the first and second semiconductor layers to expose the dummy material; removing the dummy material in the trench; depositing a conductive material in the trench; and bonding the substrate to a silicon substrate such that the conductive material is in contact with the silicon substrate. The trench extends through the third semiconductor layer and has a bottom surface on the second semiconductor layer.

Abstract: A method of reducing the distance between co-linear vertical fin field effect devices is provided. The method includes forming a first vertical fin on a substrate, forming a second vertical fin on the substrate, and depositing a masking block in the gap between the first vertical fin and second vertical fin. The method further includes depositing a spacer layer on the substrate, masking block, first vertical fin, and second vertical fin, depositing a protective liner on the spacer layer, and removing a portion of the protective liner from the spacer layer on the masking block and substrate adjacent to the first vertical fin. The method further includes removing a portion of the spacer layer from a portion the masking block and a portion of the substrate adjacent to the first vertical fin, and growing a first source/drain layer on an exposed portion of the substrate and first vertical fin.

Abstract: Structures for field effect-transistors and methods of forming field-effect transistors. A gate structure includes a gate electrode and a gate dielectric layer that are arranged between a first sidewall spacer and a second sidewall spacer. The gate structure has a top surface that is recessed relative to the first and second sidewall spacers. A gate cap is arranged over a section of the gate structure and over the first and sidewall spacers. The gate cap has a first section of a first width arranged over the section of the gate structure and a second section of a second width arranged over the section of the gate cap, the first sidewall spacer, and the second sidewall spacer. A dielectric liner is arranged between the gate cap and the gate structure, between the gate cap and the first sidewall spacer, and between the gate cap and the second sidewall spacer.

Abstract: A method, apparatus, and manufacturing system are disclosed for a fin field effect transistor having a reduced parasitic capacitance between a gate and a source/drain contact. In one embodiment, we disclose a semiconductor device including first and second fins; an isolation structure between the fins; first and second metal gates; a first dielectric body under the first metal gate and on the substrate between the first fin and the second fin, wherein a top of the first dielectric body is below a top of the first metal gate; and a second dielectric body in the second metal gate and on the substrate between the first fin and the second fin, wherein a top of the second dielectric body is at or above a top of the second metal gate.

Abstract: One illustrative method disclosed herein may include forming a first straight sidewall spacer adjacent a gate structure of a transistor, forming a recessed layer of sacrificial material adjacent the first straight sidewall spacer and forming a second straight sidewall spacer on a portion of the outer surface of the first straight sidewall spacer and above the recessed layer of sacrificial material. The method may also include removing the recessed layer of sacrificial material so as to expose a first vertical portion of the outer surface of the first straight sidewall spacer and forming an epi material on and above the substrate, wherein an edge of the epi material engages the first straight sidewall spacer.

Abstract: A semiconductor device structure is provided. The semiconductor device structure includes a gate stack over a semiconductor substrate and a source/drain structure adjacent to the gate stack. The semiconductor device structure also includes a cap element over the source/drain structure. The cap element has a first top plane and the source/drain structure has a second top plane. The first top plane of the cap element is wider than the second top plane of the source/drain structure. A surface orientation of the first top plane of the cap element and a surface orientation of a side surface of the cap element are different from each other.

Abstract: A vertical transport field effect transistor (VTFET) is provided that includes a vertical semiconductor channel material structure (i.e., fin or pillar) having a V-shaped groove located in the topmost surface thereof. A top source/drain structure is formed in contact with the V-shaped groove present in the topmost surface of the vertical semiconductor channel material structure. No drive-in anneal is needed to form the top source/drain structure. The presence of the V-shaped groove at the top junction region provides a VTFET that has improved device performance.

Abstract: A back-illuminated solid-state imaging device includes a semiconductor substrate, a shift register, and a light-shielding film. The semiconductor substrate includes a light incident surface on the back side and a light receiving portion generating a charge in accordance with light incidence. The shift register is disposed on the side of a light-detective surface opposite to the light incident surface of the semiconductor substrate. The light-shielding film is disposed on the side of the light-detective surface of the semiconductor substrate. The light-shielding film includes an uneven surface opposing the light-detective surface.

Abstract: A structure and a formation method of a semiconductor device are provided. The semiconductor device includes a semiconductor substrate and a first gate electrode over the semiconductor substrate. The semiconductor device also includes a first gate dielectric layer between the first gate electrode and the semiconductor substrate. The semiconductor device further includes a second gate electrode over the semiconductor substrate. The second gate electrode has an upper portion and a lower portion between the upper portion and the semiconductor substrate, and the upper portion is wider than the lower portion. In addition, the semiconductor device includes a second gate dielectric layer between the second gate electrode and the semiconductor substrate.

Abstract: Techniques are disclosed for transistor gate trench engineering to decrease capacitance and resistance. Sidewall spacers, sometimes referred to as gate spacers, or more generally, spacers, may be formed on either side of a transistor gate to help lower the gate-source/drain capacitance. Such spacers can define a gate trench after dummy gate materials are removed from between the spacers to form the gate trench region during a replacement gate process, for example. In some cases, to reduce resistance inside the gate trench region, techniques can be performed to form a multilayer gate or gate electrode, where the multilayer gate includes a first metal and a second metal above the first metal, where the second metal includes lower electrical resistivity properties than the first metal. In some cases, to reduce capacitance inside a transistor gate trench, techniques can be performed to form low-k dielectric material on the gate trench sidewalls.

Abstract: A semiconductor device includes a first insulating interlayer on a first region of a substrate and a second insulating interlayer on a second region of the substrate, a plurality of first wiring structures on the first insulating interlayer, the first wiring structures being spaced apart from each other, a plurality of second wiring structures filling a plurality of trenches on the second insulating interlayer, respectively, an insulation capping structure selectively on a surface of the first insulating interlayer between the first wiring structures and on a sidewall and an upper surface of each of the first wiring structures, the insulation capping structure including an insulating material, a third insulating interlayer on the first and second wiring structures, and an air gap among the first wiring structures under the third insulating interlayer.

Abstract: A method for fabricating semiconductor device includes the steps of: forming a gate structure on a substrate; forming a spacer around the gate structure; forming a first contact etch stop layer (CESL) around the spacer; forming a mask layer on the first CESL; removing part of the mask layer; removing part of the first CESL; forming a second CESL on the mask layer and the gate structure; and removing part of the second CESL.

Abstract: Embodiments disclosed herein relate generally to capping processes and structures formed thereby. In an embodiment, a conductive feature, formed in a dielectric layer, has a metallic surface, and the dielectric layer has a dielectric surface. The dielectric surface is modified to be hydrophobic by performing a surface modification treatment. After modifying the dielectric surface, a capping layer is formed on the metallic surface by performing a selective deposition process. In another embodiment, a surface of a gate structure is exposed through a dielectric layer. A capping layer is formed on the surface of the gate structure by performing a selective deposition process.

Abstract: A semiconductor device includes a substrate having an active pattern therein, a gate electrode extending across the active pattern and a source/drain region on the active pattern laterally adjacent the gate electrode. The device further includes a contact structure including a first contact on the source/drain region, a second contact on the first contact and a spacer on sidewalls of the first and second contacts.

Abstract: Present disclosure provides a hybrid semiconductor transistor structure, including a substrate, a first transistor on the substrate, a channel of the first transistor including a fin and having a first channel height, a second transistor adjacent to the first transistor, a channel of the second transistor including a nanowire, and a separation laterally spacing the fin from the nanowire. The first channel height is greater than the separation. Present disclosure also provides a method for manufacturing the hybrid semiconductor transistor structure.

Abstract: A semiconductor device includes an active pattern protruding from a substrate, a gate structure crossing over the active pattern, and source/drain regions disposed on the active pattern at opposite sides of the gate structure. Each of the source/drain regions includes a first epitaxial pattern contacting the active pattern and a second epitaxial pattern on the first epitaxial pattern. The first epitaxial pattern comprises a material having a lattice constant which is the same as that of the substrate, and the second epitaxial pattern comprises a material having a lattice constant greater than that of the first epitaxial pattern.

Abstract: A synthetic quartz glass lid is provided comprising a synthetic quartz glass and an adhesive formed on a periphery of a main surface of the window member. Further, an optical device package is provided comprising a box-shaped receptacle having an open upper end, an optical device received in the receptacle, and a window member of synthetic quartz glass bonded to the upper end of the receptacle with an adhesive. The adhesive is a low-melting metallic glass consisting of Te, Ag and at least one element selected from W, V, P, Ba, and Zr.

Abstract: In a method for manufacturing a semiconductor device, a gate structure is formed over a channel layer and an isolation insulating layer. A first sidewall spacer layer is formed on a side surface of the gate structure. A sacrificial layer is formed so that an upper portion of the gate structure with the first sidewall spacer layer is exposed from the sacrificial layer and a bottom portion of the gate structure with the first sidewall spacer layer is embedded in the first sacrificial layer. A space is formed between the bottom portion of the gate structure and the sacrificial layer by removing at least part of the first sidewall spacer layer. After the first sidewall spacer layer is removed, an air gap is formed between the bottom portion of the gate structure and the sacrificial layer by forming a second sidewall spacer layer over the gate structure.

Abstract: In a method for manufacturing a semiconductor device, a gate structure is formed over a channel layer and an isolation insulating layer. A first sidewall spacer layer is formed on a side surface of the gate structure. A sacrificial layer is formed so that an upper portion of the gate structure with the first sidewall spacer layer is exposed from the sacrificial layer and a bottom portion of the gate structure with the first sidewall spacer layer is embedded in the first sacrificial layer. A space is formed between the bottom portion of the gate structure and the sacrificial layer by removing at least part of the first sidewall spacer layer. After the first sidewall spacer layer is removed, an air gap is formed between the bottom portion of the gate structure and the sacrificial layer by forming a second sidewall spacer layer over the gate structure.

Abstract: A method for making a lithium-sulfur battery separator includes providing a separator substrate comprising a first surface and a second surface opposite to the first surface; and forming a functional layer on at least one of the first surface and the second surface. A method of forming the functional layer includes providing a carbon nanotube layer comprising a plurality of carbon nanotubes; etching the carbon nanotube layer to form defects on surfaces of the plurality of carbon nanotubes; and forming a hafnium oxide layer on the defects to form a carbon nanotube/hafnium oxide composite layer.

Abstract: A method and structure for providing uniform, large-area graphene by way of a transfer-free, direct-growth process. In some embodiments, a SAM is used as a carbon source for direct graphene synthesis on a substrate. For example, a SAM is formed on an insulating surface, and a metal layer is formed over the SAM. The metal layer may serve as a catalytic metal, whereby the SAM is converted to graphene following an annealing process. The SAM is deposited using a VPD process (e.g., an ALD process and/or an MLD process). In some embodiments, a CNT having a controlled diameter may be formed on the surface of a nanorod by appropriately tuning the geometry of the nanorod. Additionally, in some embodiments, a curved graphene transistor may be formed over a curved oxide surface, thereby providing a band gap in a channel region of the graphene transistor.

Abstract: The present disclosure relates to semiconductor structures and, more particularly, to a spacer with laminate liner and methods of manufacture. The structure includes: a replacement metal gate structure; a laminate low-k liner on the replacement metal gate structure; and a spacer on the laminate low-k liner.

Abstract: A stacked nanosheet semiconductor device and method of forming are provided. In an illustrative embodiment, a gate all around (GAA) stacked nanosheet field effect transistor (FET) includes a plurality of stacked semiconductor channel nanosheet layers and a dummy nanosheet layer formed above a top one of the stacked semiconductor channel nanosheet layers, the dummy nanosheet formed from a dielectric material. The GAA stacked nanosheet FET also includes a high dielectric constant (high-k) material formed around each of the plurality of stacked semiconductor channel nanosheet layers and around the dummy nanosheet layer and a first work function (WF) metal formed around the plurality of stacked semiconductor channel nanosheet layers and the dummy nanosheet layer.

Abstract: A semiconductor structure includes a gate structure over a substrate. The semiconductor structure includes an inter-layer dielectric (ILD) over the substrate, wherein an upper portion of the ILD has a higher concentration of silicon atoms than a bottom portion of the ILD.

Abstract: Methods for forming semiconductor structures are provided. The method includes forming a fin structure over a substrate and forming a gate structure across the fin structure. The method further includes recessing the fin structure to form a recess and implanting dopants from the recess to form a doped region. The method further includes diffusing the dopants in the doped region to form an expanded doped region and forming a source/drain structure over the expanded doped region.

Abstract: Methods and apparatus to form films on sensitive substrates while preventing damage to the sensitive substrate are provided herein. In certain embodiments, methods involve forming a bilayer film on a sensitive substrate that both protects the underlying substrate from damage and possesses desired electrical properties. Also provided are methods and apparatus for evaluating and optimizing the films, including methods to evaluate the amount of substrate damage resulting from a particular deposition process and methods to determine the minimum thickness of a protective layer. The methods and apparatus described herein may be used to deposit films on a variety of sensitive materials such as silicon, cobalt, germanium-antimony-tellerium, silicon-germanium, silicon nitride, silicon carbide, tungsten, titanium, tantalum, chromium, nickel, palladium, ruthenium, or silicon oxide.

Abstract: This disclosure is directed to an integrated circuit (IC) structure. The IC structure may include a semiconductor substrate having a first fin and a second fin spaced from the first fin; a first source/drain region in the first fin, the first source/drain region encompassing a top surface and two opposing lateral sides of the first fin; a second source/drain region in the second fin, the second source/drain encompassing a top surface and two opposing lateral sides of the second fin; and a metal contact extending over the first source/drain region and the second source/drain region and surrounding the top surface and at least a portion of the two opposing lateral sides of each of the first and the second source/drain regions.

Abstract: A vertical transport field-effect transistor includes gate metal protected by a conformal encapsulation layer. Techniques for fabricating the transistor include depositing the conformal encapsulation layer over the gate metal prior to depositing an additional encapsulation layer such as a nitride layer. The conformal encapsulation layer protects the gate metal during deposition of the additional encapsulation layer, thereby avoiding oxidation or nitridation of the gate metal. The conformal encapsulation layer may be an amorphous silicon layer deposited at relatively low temperature.

Abstract: A method includes forming a semiconductor fin over a substrate; forming a helmet stack on a top surface of the semiconductor fin; forming a spacer layer over the helmet stack and on opposite sidewalls of the semiconductor fin; and etching the helmet layer and the spacer layer to expose the top surface and the sidewalls of the semiconductor fin.

Abstract: Semiconductor devices are described that have a metal interconnect extending vertically through a portion of the device to the back side of a semiconductor substrate. A top region of the metal interconnect is located vertically below a horizontal plane containing a metal routing layer. Method of fabricating the semiconductor device can include etching a via into a semiconductor substrate, filling the via with a metal material, forming a metal routing layer subsequent to filling the via, and removing a portion of a bottom of the semiconductor substrate to expose a bottom region of the metal filled via.

Abstract: Structures and formation methods of a semiconductor device structure are provided. The semiconductor device structure includes a semiconductor substrate and a first gate stack over the semiconductor substrate. The first gate stack includes a metal electrode. The semiconductor device structure also includes a second gate stack over the semiconductor substrate, and the second gate stack includes a polysilicon element.

Abstract: Embodiments of the disclosure are in the field of advanced integrated circuit structure fabrication and, in particular, 10 nanometer node and smaller integrated circuit structure fabrication and the resulting structures. In an example, an integrated circuit structure includes a first isolation structure over a first end of a fin. A gate structure is over the fin and is spaced apart from the first isolation structure along the direction. A second isolation structure is over a second end of the fin, the second end opposite the first end. The second isolation structure is spaced apart from the gate structure. The first isolation structure and the second isolation structure both comprise a first dielectric material laterally surrounding a recessed second dielectric material distinct from the first dielectric material. The recessed second dielectric material laterally surrounds at least a portion of a third dielectric material different from the first and second dielectric materials.

Abstract: A complimentary metal-oxide-semiconductor (CMOS) circuit including: a substrate; and a plurality of field-effect transistors on the substrate. Each of the field-effect transistors includes: a plurality of contacts; a source connected to one of the contacts; a drain connected to another one of the contacts; a gate; and a spacer between the gate and the contacts. The spacer of one of the field-effect transistors has a larger airgap than the spacer of another one of the field-effect transistors.

Abstract: Methods of forming a structure that includes a field-effect transistor and structures that include a field effect-transistor. A cut is formed that extends through a gate structure of the field-effect transistor such that a gate electrode of the gate structure is divided into a first section having a first surface and a second section having a second surface spaced across the cut from the first surface. After forming the cut, a first section of a conductive layer is selectively deposited on the first surface of the first section of the gate electrode and a second section of the conductive layer is selectively deposited on the second surface of the second section of the gate electrode to shorten the cut. A dielectric material is deposited in the cut between the first and second sections of the conductive layer on the first and second surfaces of the gate electrode to form a dielectric pillar.

Abstract: A method of fabricating semiconductor devices is provided. The method includes forming a fin protruding from a substrate, and forming a disposable mandrel fin on the fin. The method also includes epitaxially growing channel fins on sidewalls of the disposable mandrel fin. The method further includes removing the disposable mandrel fin to form a space between the channel fins, and forming a gate structure to fill the space between the channel fins and to wrap the channel fins. In addition, the method includes forming source and drain structures on opposite sides of the gate structure.

Abstract: A method of manufacturing a field effect transistor is provided, including supplying a substrate surmounted by first, second, and third structures, the second structure arranged between the first and the third structures and including at least one first nano-object located away from the substrate, a part of the first nano-object being configured to form a channel area of the transistor; forming electrodes of the transistor including epitaxial growth of a first material to obtain a first continuity of matter made of the first material between the second structure and the first structure, and to obtain a second continuity of matter made of the first material between the second structure and the third structure; and epitaxial growth of a second material, starting from the first material, the second material having a lattice parameter different from a lattice parameter of the first material of the first and the second continuities.

Abstract: A semiconductor device is provided. The semiconductor device includes a substrate, a semiconductor fin, a first gate stack, and a first metal element-containing dielectric mask. The semiconductor fin protrudes from the substrate. The first gate stack is over the semiconductor fin. The first metal element-containing dielectric mask is over the first gate stack.

Abstract: Embodiments of the invention are directed to a semiconductor device that includes a substrate formed from a first type of semiconductor material, along with a fin formed on the substrate. The fin includes a fin channel region configured to include a bottom region, a central region, and a top active region. The central region includes a dielectric material and couples the bottom region to the top active region. The top active region includes a second type of semiconductor material, and the bottom region includes a third type of semiconductor material.