Transistor and methods of forming transistors

A transistor comprises a top source/drain region, a bottom source/drain region, and a channel region vertically between the top and bottom source/drain regions. A gate is operatively laterally-adjacent the channel region. The top source/drain region, the bottom source/drain region, and the channel region respectively have crystal grains and grain boundaries between immediately-adjacent of the crystal grains. At least one of the bottom source/drain region and the channel region has an internal interface there-within between the crystal grains that are above the internal interface and the crystal grains that are below the internal interface. At least some of the crystal grains that are immediately-above the internal interface physically contact at least some of the crystal grains that are immediately-below the internal interface. All of the grain boundaries that are between immediately-adjacent of the physically-contacting crystal grains that are immediately-above and that are immediately-below the interface align relative one another. The internal interface comprises at least one of (a) and (b), where (a): conductivity-modifying dopant concentration immediately-above the internal interface is lower than immediately-below the internal interface and (b): a laterally-discontinuous insulative oxide. Other embodiments, including method, are disclosed.

TECHNICAL FIELD

Embodiments disclosed herein pertain to transistors and to methods of forming transistors

BACKGROUND

Memory cells may be volatile, semi-volatile, or non-volatile. Non-volatile memory cells can store data for extended periods of time in the absence of power. Non-volatile memory is conventionally specified to be memory having a retention time of at least about 10 years. Volatile memory dissipates and is therefore refreshed/rewritten to maintain data storage. Volatile memory may have a retention time of milliseconds or less. Regardless, memory cells are configured to retain or store memory in at least two different selectable states. In a binary system, the states are considered as either a “0” or a “1”. In other systems, at least some individual memory cells may be configured to store more than two levels or states of information.

A field effect transistor is one type of electronic component that may be used in a memory cell. These transistors comprise a pair of conductive source/drain regions having a semiconductive channel region there-between. A conductive gate is adjacent the channel region and separated therefrom by a thin gate insulator. Application of a suitable voltage to the gate allows current to flow from one of the source/drain regions to the other through the channel region. When the voltage is removed from the gate, current is largely prevented from flowing through the channel region. Field effect transistors may also include additional structure, for example a reversibly programmable charge-storage region as part of the gate construction between the gate insulator and the conductive gate. Field effect transistors are of course also used in integrated circuitry other than and/or outside of memory circuitry.

DETAILED DESCRIPTION OF EXAMPLE EMBODIMENTS

Embodiments of the invention encompass methods of forming one or more transistors and one or more transistors independent of method of manufacture. Transistors manufactured in accordance with method embodiments may have any of the attributes as described herein in structure embodiments. A first example transistor14in accordance with an embodiment of the invention as part of a construction10is shown inFIG. 1. Construction10comprises a base substrate11having any one or more of conductive/conductor/conducting, semiconductive/semiconductor/semiconducting, or insulative/insulator/insulating (i.e., electrically herein) material(s)12. Various materials have been formed elevationally over base substrate11. Materials may be aside, elevationally inward, or elevationally outward of theFIG. 1—depicted materials. For example, other partially or wholly fabricated components of integrated circuitry may be provided somewhere above, about, or within base substrate11. Only one transistor14is shown, although construction10may comprise multiple of the same or different construction transistors, for example fabricated in an array which includes one or more transistors in accordance with the invention.

Transistor14comprises a top source/drain region16, a bottom source/drain region18, a channel region20vertically between top and bottom source/drain regions16,18, respectively, and a gate22(i.e., conductive material) operatively laterally-adjacent channel region20. A gate insulator24(e.g., silicon dioxide and/or silicon nitride) is between gate22and channel region20. The example depicted components for brevity and clarity are only shown inFIG. 1as a vertical cross-section. The example source/drain regions and channel regions may be, for example, in the form of coextensive longitudinally elongated lines running into and out of the plane of the page upon whichFIG. 1lies. Alternately and by way of example only, such may be circular, rectangular, elliptical, triangular, etc. in horizontal cross-section (not shown). Gate insulator24and/or gate22may peripherally encircle such structures or alternately, by way of example only, be only partially around such structures or only on one lateral-side in vertical cross-section (not shown). Top source/drain region16and channel region20may be considered as having a top interface38and bottom source/drain region18and channel region20may be considered as having a bottom interface40. Interfaces38and/or40are shown as being flat and horizontal, although other oriented interfaces may be used, for example diagonal, a jagged and/or undulating interface, a combination of straight and curved segments, etc, By way of examples only, regions16,18, and20may comprise one or more of elemental-form silicon, elemental-form germanium, a mixture of silicon and germanium, etc.

Top source/drain region16, bottom source/drain region18, and channel region20respectively have crystal grains30and grain boundaries32between immediately-adjacent crystal grains30. Ideally, such regions are each entirely crystalline. In this document, “crystalline” not immediately preceded by a numerical percentage or other quantifying adjective is a material, region, and/or structure that is at least 90% by volume crystalline (i.e., having at least 90% by volume crystal grains), Two or three of regions16,18,20may have the same or different average crystal grain size(s) (i.e., volumetric) relative one another. Regardless, in one embodiment, all of grain boundaries32that are between immediately-adjacent crystal grains30at one of interfaces38and40(at least one and both as shown) align relative one another. Alternately, in another embodiment, all of grain boundaries32that are between immediately-adjacent crystal grains30at one of interfaces38and40(at least one and including both) do not align relative one another (not shown).

At least one of bottom source/drain region18and channel region20(bottom source/drain region18as shown) has an internal interface36there-within (i.e., such interface being between and not comprising part of the respective top or bottom/base of such bottom source/drain region and/or channel region) between crystal grains30that are above internal interface36and crystal grains30that are below internal interface36. At least some of crystal grains30that are immediately-above interface36physically contact at least some of crystal grains30that are immediately-below interface36. In the context of this document as respects “immediately-above” and “immediately-below” and crystal grains, such means no other crystal grain is between the interface and said crystal grain that is immediately-above or immediately-below the interface. All of grain boundaries32that are between immediately-adjacent of the physically-contacting crystal grains30that are immediately-above and that are immediately-below interface36align relative one another. Internal interface36comprises at least one of (a) and (b) where; (a): conductivity-modifying dopant concentration immediately-above the interface is lower than immediately-below the interface, and (b): a laterally-discontinuous insulative oxide (e.g., silicon dioxide). In one embodiment, the conductivity-modifying dopant is immediately-above and immediately-below the interface, and the internal interface comprises both of (a) and (b). In one embodiment, at least one of the bottom source/drain region and the channel region is monocrystalline and in one such embodiment each of the bottom source/drain region and the channel region is monocrystalline. In one embodiment, at least one of the bottom source/drain region and the channel region is polycrystalline, and in one such embodiment each of the bottom source/drain region and the channel region is polycrystalline.

FIG. 1shows an example embodiment wherein internal interface36is within bottom source/drain region18, and comprising (a), wherein conductivity-modifying dopant is immediately-above and immediately-below interface36. By way of example only, internal interface36is shown as being horizontal and half-way between a top and bottom/base of bottom source/drain region18. Such may be otherwise oriented and/or positioned.FIG. 1also shows an example embodiment wherein each of crystal grains30that is immediately-above interface36physically contacts one of crystal grains30that is immediately-below interface36. Any other attribute(s) or aspect(s) as shown and/or described herein with respect to other embodiments may be used.

An alternate embodiment construction is shown inFIG. 2. Like numerals from the above-described embodiments have been used where appropriate, with some construction differences being indicated with the suffix “a”. Construction10ashows a transistor14awherein internal interface36is within channel region20a.FIG. 3shows an alternate example construction10bcomprising a transistor14bwherein each of bottom source/drain region18and channel region20ahas such an internal interface36. Like numerals from the above-described embodiments have been used where appropriate, with some construction differences being indicated with the suffix “b”. Any other attribute(s) or aspect(s) as shown and/or described herein with respect to other embodiments may be used. Any other attribute(s) or aspect(s) as shown and/or described herein with respect to other embodiments may be used.

FIG. 4shows another example construction10ccomprising a transistor14cin accordance with an embodiment of the invention. Like numerals from the above-described embodiments have been used where appropriate, with some construction differences being indicated with the suffix “c” or with different numerals. Transistor14ccomprises (b): a laterally-discontinuous insulative oxide35comprising internal interface36c. Interface36cmay be considered as any of tops, bottoms, or going laterally though laterally-discontinuous insulative oxide35.

FIG. 4shows an example embodiment wherein laterally-discontinuous insulative oxide35occupies less than a majority of interface36c, and in one such embodiment as shown wherein laterally-discontinuous insulative oxide35occupies no more than 25% of such interface.FIG. 5shows an alternate example embodiment construction10dcomprising a transistor14dwherein laterally-discontinuous insulative oxide35occupies a majority of interface36d. Like numerals from the above-described embodiments have been used where appropriate, with some construction differences being indicated with the suffix “d”. Any other attribute(s) or aspect(s) as shown and/or described herein with respect to other embodiments may be used.

Another alternate embodiment construction10ecomprising a transistor14eis shown inFIG. 6. Like numerals from the above-described embodiments have been used where appropriate, with some construction differences being indicated with the suffix “e”. At least one of top interface38and bottom interface40(top interface38as shown) comprises a laterally-discontinuous insulative oxide35.FIG. 7shows an alternate embodiment construction10fcomprising a transistor14fwherein bottom interface40fcomprises laterally-discontinuous insulative oxide35, withFIG. 8showing another alternate construction10gcomprising a transistor14bwherein each of top interface38and bottom interface40comprise a laterally-discontinuous insulative oxide35. Like numerals from the above-described embodiments have been used where appropriate, with some construction differences being indicated with the suffix's “f” and “g”, respectively. In one embodiment wherein each of the top and bottom interfaces comprises the laterally-discontinuous insulative oxide, such are of the same composition relative one another and in another embodiment are of different compositions relative one another. An internal interface36(not shown) may be provided within at least one of bottom source/drain region18and channel region20, for example as described above, and any other attribute(s) or aspect(s) as shown and/or described herein with respect to other embodiments may be used.

Any of the upper source/drain region, the bottom source/drain region, and/or the channel region vertically-therebetween may have a plurality of vertically-elongated crystal grains that individually are directly against both of their respective top or bottom and the immediately-adjacent source/drain region(s) or channel region (e.g., at any of interfaces38,38e,40,40f, and not shown). Alternately and/or additionally, if an internal interface is present, there may be a plurality of vertically-elongated crystal grains that individually are directly against such internal interface and the respective top or bottom of such source/drain region or channel region (not shown). Such may exist above, below, or both above and below such an internal interface.

Embodiments of the invention encompass a method of forming a transistor, for example any of the transistors described above and shown in the figures. An example such method is next described with references toFIGS. 9-12. Like numerals for predecessor constructions have been used where appropriate.

Referring toFIG. 9, a bottom crystalline seed material50has been formed above substrate11as part of a construction10h(which, for example, may be a predecessor to any of constructions10,10a,10b,10c,10d,10e,10f,10g). Bottom crystalline seed material50has bottom-material crystal grains30and bottom-material crystal grain boundaries32between immediately-adjacent bottom-material crystal grains30. By way of examples only, bottom crystalline seed material50may be a layer that comprises that portion of bottom source/drain region18,18c,18dthat is below internal interface36,36c,36dinFIGS. 1-5above (e.g., alone or in combination with channel material). Alternately, and by way of examples only, bottom crystalline seed material50may comprise all of bottom source/drain region18below bottom interface40in any of the above-described embodiments. Regardless, ideally bottom crystalline seed material50is formed at low temperature (e.g., below 600° C. and ideally below 450° C.) using solid phase crystallography or solid phase epitaxy with or without laser-assisted crystallization, including any other existing or future developed method(s).

Referring toFIG. 10, and in one embodiment, amorphous material52has been formed atop and directly against bottom crystalline seed material50, In this document, a material, region, and/or structure is “amorphous” if such is at least 90% by volume amorphous. In some embodiments, material52may be considered as target material52and regardless of whether such material is amorphous, crystalline, or some combination thereof. Regardless, material52may be formed, for example, of a thickness of material of bottom source/drain region18,18c,18dabove internal interface36,36c,36dup to bottom interface40. Alternately, as examples, material52may be formed to a thickness which is greater than such portion of bottom source/drain region18,18c,18dabove internal interface36,36c,36dto include part or all of thickness of channel region20,20a, and including upwardly to include some or all of the thickness of top source/drain region16. Accordingly, and as will be apparent from the continuing discussion, material52may subsequently be transformed to comprise at least some part of a bottom source/drain region, a channel region, and/or an top source/drain region of a vertical transistor. Regardless, all or one or more portions of material52may be doped or undoped at this point in processing. In this document, “undoped” means from zero percent up to no greater than 0.1 molar percent of any and all conductivity-modifying dopant (e.g., phosphorus, arsenic, etc.), with “doped” meaning more than 0.1 molar percent of any and all conductivity-modifying dopant.

Referring toFIG. 11, material52has been laser annealed, (as indicated by example downwardly-directed arrows55) to render material52molten. By way of examples only, laser annealing may use a wavelength between 200 and 700 nanometers, power at 0.1 to 2 J/cm2(ideally, 0.5 to 2 J/cm2), pulse width 5 to 250 nanoseconds, number of laser shots 1 to 100, and substrate temperature from room temperature to 450° C. Laser power for all anneals herein can be varied as selected by the artisan to control surface roughness of interfaces and grain size of the layer(s) being laser annealed. Additionally, substrate temperature may be varied for different laser shots, as may laser power and/or pulse width. Molten material52, regardless of amorphous vs. crystallinity before the laser annealing, will be amorphous the result of melting. In one embodiment, such laser annealing does not melt any of bottom crystalline seed material50there-below. In an alternate embodiment, the laser annealing of material52melts an uppermost portion of bottom crystalline seed material50there-below. Any regions within material52immediately-prior to the laser annealing that may doped to different respective concentrations will have a tendency to diffuse such dopants throughout molten material52, although not-necessarily to result in homogeneity with respect to dopant concentration in previously different concentration regions.

Referring toFIG. 12, formerly molten material52(not shown) has been cooled to form crystalline material54, in some embodiments referred to as target crystalline material54. At least a lower portion of material54can be considered as mid crystalline material that physically contacts and has crystallinity the same as that of bottom crystalline seed material50. Accordingly, mid crystalline material54will have mid-material crystal grains30and mid-material grain boundaries32between immediately-adjacent mid-material crystal grains30. Mid crystalline material54and bottom crystalline seed material50have an interface36(or36c,36d,38e, or40f, and not shown) there-between. At least some of mid-material crystal grains30that are immediately-above such interface physically contact at least some of bottom-material crystal grains30that are immediately-below such interface. All of mid-material grain boundaries32that are between immediately-adjacent mid-material crystal grains30that physically contact bottom-material crystal grains30that are immediately-below such interface align with all of bottom-material grain boundaries32that are between immediately-adjacent bottom-material crystal grains32that physically contact mid-material crystal grains30that are immediately-above such interface36. The interface, again, comprises at least one of (a) and (b), where: (a): conductivity-modifying dopant concentration immediately-above the interface is lower than immediately-below the interface; and (b): a laterally-discontinuous insulative oxide. In one embodiment, the interface is formed to be an internal interface that is within what is or will be bottom source/drain region18,18c,18d. Alternately, the interface is formed to be an internal interface that is within channel region20a. Alternately, the interface is formed to be one of interfaces40,40f,38, or38e. Any other attribute(s) or aspect(s) as shown and/or described herein with respect to other embodiments may be used.

The transistor being formed is ultimately formed to comprise a top source/drain region (e.g.,16), a bottom source/drain region (e.g.,18,18a,18c,18d), and a channel region (e.g.,20,20a) vertically between the top and bottom source/drain regions. At least a portion of the bottom crystalline seed material comprises at least a part of at least one of the top source/drain region, the bottom source/drain region, and the channel region. At least a portion of the mid crystalline material comprises at least a part of at least one of the top source/drain region, the bottom source/drain region, and the channel region. Regardless, a gate insulator (e.g.,24) and a gate (e.g.,22) are ultimately formed laterally-adjacent the channel region, for example to ultimately form any of constructions10,10a,10b,10c,10d,10e,10f,10g. Any other attribute(s) or aspect(s) as shown and/or described herein with respect to other embodiments may be used.

An additional embodiment is next described with references toFIGS. 13-17, Like numerals from the above-described embodiments have been used where appropriate, with some construction differences being indicated with the suffix “k” or with different numerals.FIG. 13shows the same processing as depicted byFIG. 9wherein a crystalline seed material50has been formed, however which in this embodiment that comprises a lower crystalline seed material as another crystalline seed material will be formed immediately-above and there-from such that the bottom crystalline seed material comprises a composite of at least two time-spaced formed materials that may be of the same or different composition(s) relative one another as will be apparent from the continuing discussion.

Referring toFIG. 14, an upper crystalline seed material58has been epitaxially grown from lower crystalline seed material50, forming an interface36(or36c,36d,38e, or40f, and not shown) there-between analogous to the processing described above with respect toFIG. 10, Material58may ultimately form an upper portion of bottom source/drain region18,18c,18d; a lower portion or all of channel region20,20a; or at least an upper portion of upper crystalline seed material58may comprise at least a lower portion of top source/drain region16. Regardless, upper crystalline seed material58may have all or portions thereof doped or undoped with conductivity modifying impurity at this point in processing. Further, ideally upper crystalline seed material58is formed at low temperature (e.g., below 600° C. and ideally below 450° C.) using solid phase crystallography or solid phase epitaxy with or without laser-assisted crystallization, including any other existing or future developed method(s).

Referring toFIG. 15, amorphous and/or target material52has been formed atop and directly against epitaxially-grown upper crystalline seed material58.

Referring toFIGS. 16 and 17, material52has been laser annealed and thereafter cooled to produce a construction as appearing inFIG. 17(e.g., having another an interface36[or36c,36d,38e, or40f, and not shown]). In one embodiment, at least an upper portion of epitaxially-grown upper crystalline seed material58is formed to comprise the channel region. In one such embodiment, at least a lower portion of epitaxially-grown upper crystalline seed material58is formed to comprise the channel region and at least a lower portion of mid crystalline material54is formed to comprise the top source/drain region. In another such embodiment, a lower portion of epitaxially-grown upper crystalline seed material58is formed to comprise the bottom source/drain region. In one embodiment, a lower portion of mid crystalline material54is formed to comprise the channel region and an uppermost portion of mid crystalline material54is formed to comprise the top source/drain region. Any other attribute(s) or aspect(s) as shown and/or described herein with respect to other embodiments may be used.

Provision of an epitaxially-grown upper crystalline seed material58resulting in formation of interfaces36(and/or36c,36d,38e, or40f, and not shown) may result in such being an effective diffusion barrier between materials58and50to preclude unwanted diffusion of conductivity modifying dopant among the depicted three example regions. Regardless, subsequent diffusion doping or ion implantation may be conducted with respect to any of the above-described embodiments. Any other attribute(s) or aspect(s) as shown and/or described herein with respect to other embodiments may be used.

An embodiment of the invention comprises a method used in forming at least a portion of a vertical transistor (e.g.,14,14a,14b,14c,14d,14e,14f,14g), with the portion comprising at least part of a top source/drain region (e.g.,16), at least part of a bottom source/drain region (e.g.,18,18a,18c,18d), or at least part of a channel region (e.g.,20,20a) vertically between the top and bottom source/drain regions. Such a method comprises forming a bottom crystalline seed material (e.g.,50alone or a combination of50and58), for example above a substrate (e.g.,11). A target material (e.g.,52) is formed atop and directly against the bottom crystalline seed material. Laser annealing is conducted of the target material to render it molten. In one embodiment, the target material is amorphous at start of the laser annealing and in another embodiment is crystalline at start of the laser annealing. In one embodiment, the bottom crystalline seed material and the target material are of the same chemical composition at start of the laser annealing, and in one such embodiment such chemical composition comprises silicon and which in one such embodiment is elemental-form silicon. The bottom crystalline seed material is used as a template while cooling the molten target material to epitaxially form target crystalline material physically contacting and having crystallinity the same as that of the bottom crystalline seed material. Any other attribute(s) or aspect(s) as shown and/or described herein with respect to other embodiments may be used.

The above-shown method embodiments ofFIGS. 9-17illustrate an example bottom seed material50or50/58as being formed as a laterally-continuous layer over substrate11. Alternately, the bottom seed material might be formed as a laterally-discontinuous layer. For example,FIG. 18shows an alternate example embodiment construction10mcorresponding to that ofFIG. 9but where bottom seed material50mis laterally-discontinuous. Like numerals from the above-described embodiments have been used where appropriate, with some construction differences being indicated with the suffix “m”. Such may provide some (or more of some) grain boundaries32of individual crystal grains30that are diagonally-oriented and/or laterally-oriented at outermost surfaces of the bottom seed material than otherwise occurs when an outermost surface thereof is laterally-continuous. This may advantageously provide additional diagonal-like and/or lateral crystalline propagation that may accelerate total crystalline propagation from seed material50or50/58. Any other attribute(s) or aspect(s) as shown and/or described herein with respect to other embodiments may be used.

The above processing(s) or construction(s) may be considered as being relative to an array of components formed as or within a single stack or single deck of such components above or as part of an underlying base substrate (albeit, the single stack/deck may have multiple tiers). Control and/or other peripheral circuitry for operating or accessing such components within an array may also be formed anywhere as part of the finished construction, and in some embodiments may be under the array (e.g., CMOS under-array). Regardless, one or more additional such stack(s)/deck(s) may be provided or fabricated above and/or below that shown in the figures or described above. Further, the array(s) of components may be the same or different relative one another in different stacks/decks. Intervening structure may be provided between immediately-vertically-adjacent stacks/decks (e.g., additional circuitry and/or dielectric layers). Also, different stacks/decks may be electrically coupled relative one another. The multiple stacks/decks may be fabricated separately and sequentially (e.g., one atop another), or two or more stacks/decks may be fabricated at essentially the same time.

The assemblies and structures discussed above may be used in integrated circuits/circuitry and may be incorporated into electronic systems. Such electronic systems may be used in, for example, memory modules, device drivers, power modules, communication modems, processor modules, and application-specific modules, and may include multilayer, multichip modules. The electronic systems may be any of a broad range of systems, such as, for example, cameras, wireless devices, displays, chip sets, set top boxes, games, lighting, vehicles, clocks, televisions, cell phones, personal computers, automobiles, industrial control systems, aircraft, etc.

Further, “directly above”, “directly below”, and “directly under” require at least some lateral overlap (i.e., horizontally) of two stated regions/materials/components relative one another. Also, use of “above” not preceded by “directly” only requires that some portion of the stated region/material/component that is above the other be elevationally outward of the other (i.e., independent of whether there is any lateral overlap of the two stated regions/materials/components). Analogously, use of “below” and “under” not preceded by “directly” only requires that some portion of the stated region/material/component that is below/under the other be elevationally inward of the other (i.e., independent of whether there is any lateral overlap of the two stated regions/material s/components).

Any of the materials, regions, and structures described herein may be homogenous or non-homogenous, and regardless may be continuous or discontinuous over any material which such overlie. Where one or more example composition(s) is/are provided for any material, that material may comprise, consist essentially of, or consist of such one or more composition(s). Further, unless otherwise stated, each material may be formed using any suitable existing or future-developed technique, with atomic layer deposition, chemical vapor deposition, physical vapor deposition, epitaxial growth, diffusion doping, and ion implanting being examples.

The composition of any of the conductive/conductor/conducting materials herein may be metal material and/or conductively-doped semiconductive/semiconductor/semiconducting material. “Metal material” is any one or combination of an elemental metal, any mixture or alloy of two or more elemental metals, and any one or more conductive metal compound(s).

Herein, “selective” as to etch, etching, removing, removal, depositing, forming, and/or formation is such an act of one stated material relative to another stated material(s) so acted upon at a rate of at least 2:1 by volume. Further, selectively depositing, selectively growing, or selectively forming is depositing, growing, or forming one material relative to another stated material or materials at a rate of at least 2:1 by volume for at least the first 75 Angstroms of depositing, growing, or forming.

Unless otherwise indicated, use of “or” herein encompasses either and both.

CONCLUSION

In some embodiments, a transistor comprises a top source/drain region, a bottom source/drain region, and a channel region vertically between the top and bottom source/drain regions. A gate is operatively laterally-adjacent the channel region. The top source/drain region, the bottom source/drain region, and the channel region respectively have crystal grains and grain boundaries between immediately-adjacent of the crystal grains. At least one of the bottom source/drain region and the channel region has an internal interface there-within between the crystal grains that are above the internal interface and the crystal grains that are below the internal interface. At least some of the crystal grains that are immediately-above the internal interface physically contact at least some of the crystal grains that are immediately-below the internal interface. All of the grain boundaries that are between immediately-adjacent of the physically-contacting crystal grains that are immediately-above and that are immediately-below the interface align relative one another. The internal interface comprises at least one of (a) and (b), where (a): conductivity-modifying dopant concentration immediately-above the internal interface is lower than immediately-below the internal interface and (b): a laterally-discontinuous insulative oxide.

In some embodiments, a transistor comprises a top source/drain region, a bottom source/drain region, and a channel region vertically between the top and bottom source/drain regions. A gate is operatively laterally-adjacent the channel region. The top source/drain region, the bottom source/drain region, and the channel region respectively have crystal grains and grain boundaries between immediately-adjacent of the crystal grains. The top source/drain region and the channel region have a top interface and the bottom source/drain region and the channel region have a bottom interface. At least one of the top interface and the bottom interface comprise a laterally-discontinuous insulative oxide.

In some embodiments, a method is used in forming at least a portion of a vertical transistor, where the portion comprises at least part of a top source/drain region, at least part of a bottom source/drain region, or at least part of a channel region vertically between the top and bottom source/drain regions. The method comprises forming a bottom crystalline seed material. Target material is formed atop and directly against the bottom crystalline seed material. The target material is laser annealed to render it molten. The bottom crystalline seed material is used as a template while cooling the molten target material to epitaxially form target crystalline material that physically contacts and has crystallinity the same as that of the bottom crystalline seed material.

In some embodiments, a method of forming a transistor comprises forming a bottom crystalline seed material. The bottom crystalline seed material has bottom-material crystal grains and bottom-material grain boundaries between immediately-adjacent of the bottom-material crystal grain. Amorphous material is formed atop and directly against the bottom crystalline seed material. The amorphous material is laser annealed to render it molten. The molten amorphous material is cooled to form mid crystalline material that physically contacts and has crystallinity the same as that as the bottom crystalline seed material. The mid crystalline material has mid-material crystal grains and mid-material grain boundaries between immediately-adjacent of the mid-material crystal grains. The mid crystalline material and the bottom crystalline seed material have an interface there-between. At least some of the mid-material crystal grains that are immediately-above the interface physically contact at least some of the bottom-material crystal grains that are immediately-below the interface. All of the mid-material grain boundaries that are between immediately-adjacent of the mid-material crystal grains that physically contact the bottom-material crystal grains that are immediately-below the interface align with all of the bottom-material grain boundaries that are between immediately-adjacent of the bottom-material crystal grains that physically contact the mid-material crystal grains that are immediately-above the interface. The interface comprises at least one of (a) and (b), where (a): conductivity-modifying dopant concentration immediately-above the interface is lower than immediately-below the interface and (b): a laterally-discontinuous insulative oxide. The transistor is formed to comprise a top source/drain region, a bottom source/drain region, and a channel region vertically between the top and bottom source/drain regions. At least a portion of the bottom crystalline seed material comprises at least a part of at least one of the top source/drain region, the bottom source/drain region, and the channel region. At least a portion of the mid crystalline material comprises at least a part of at least one of the top source/drain region, the bottom source/drain region, and the channel region. A gate insulator and a gate are formed laterally-adjacent the channel region.