Abstract: An integrated circuit containing PMOS transistors may be formed by forming a dual layer hard mask. A first layer of the hard mask is halogen-containing silicon nitride formed using a halogenated silane reagent. A second layer of the hard mask is silicon nitride formed on the first layer using halogen-free reagents. After source/drain cavities are etched in the PMOS transistors, a pre-epitaxial bake with hydrogen is performed. After SiGe epitaxial source/drain regions are formed, the hard mask is removed.

Abstract: A semiconductor device includes a fin structure disposed over a substrate, a gate structure and a source. The fin structure includes an upper layer being exposed from an isolation insulating layer. The gate structure disposed over part of the upper layer of the fin structure. The source includes the upper layer of the fin structure not covered by the gate structure. The upper layer of the fin structure of the source is covered by a crystal semiconductor layer. The crystal semiconductor layer is covered by a silicide layer formed by Si and a first metal element. The silicide layer is covered by a first metal layer. A second metal layer made of the first metal element is disposed between the first metal layer and the isolation insulating layer.

Abstract: A method for fabricating semiconductor device includes the steps of: providing a substrate having at least one fin-shaped structure thereon, wherein the fin-shaped structure comprises a top portion and a bottom portion; removing part of the bottom portion of the fin-shaped structure; forming an epitaxial layer on the substrate to surround the bottom portion of the fin-shaped structure; transforming the bottom portion of the fin-shaped structure into the epitaxial layer; and removing part of the epitaxial layer.

Abstract: A shunt capacitor is connected to a wireless charging resonator to prevent harmonics emitted from a power amplifier from radiating to the outside, and at least one circuit having a high impedance relative to a Near Field Wireless Communication (NFC) frequency band is formed at a front side or a rear side of the shunt capacitor for solving the problems of radiating noise components due to wireless charging and of lowering an NFC signal and a power transmission intensity due to a concurrent interference between a wireless charging resonator and an NFC antenna.

Abstract: A semiconductor device having a stressor is provided. A first trench and a second trench spaced apart from each other are formed in a substrate. A channel area is defined between the first trench and the second trench. A gate dielectric layer is formed on the channel area. A gate electrode is formed on the gate dielectric layer. The stressor includes a plurality of semiconductor layers formed in the first trench and the second trench and a plurality of interlayers formed between the semiconductor layers. Sidewalls of the first trench and the second trench are v-shaped (e.g., have a < or > shape).

Abstract: A method for fabricating a semiconductor device, includes providing a strained silicon on insulator (SSOI) structure, the SSOI structure comprises, a dielectric layer disposed on a substrate, a silicon germanium layer disposed on the dielectric layer, and a strained semiconductor material layer disposed directly on the silicon germanium layer, forming a plurality of fins on the SSOI structure, forming a gate structure over a portion of at least one fin in a nFET region, forming a gate structure over a portion of at least one fin in a pFET region, removing the gate structure over the portion of the at least one fin in the pFET region, removing the silicon germanium layer exposed by the removing, and forming a new gate structure over the portion of the at least one fin in the pFET region, such that the new gate structure surrounds the portion on all four sides.

Abstract: Disclosed are isolation techniques for bulk FinFETs. A semiconductor device includes a semiconductor substrate with a fin structure on the semiconductor substrate. The fin structure is perpendicular to the semiconductor substrate and has an upper portion and a lower portion. Source and drain regions are adjacent to the fin structure. A gate structure surrounds the upper portion of the fin structure. A well contact point is provided in the semiconductor substrate. The lower portion of the fin structure includes a sub-fin between the region surrounded by the gate structure and the semiconductor substrate. The sub-fin directly contacts the semiconductor substrate. The upper portion of the fin structure and an upper portion of the sub-fin are undoped. A lower portion of the sub-fin may be doped. Electrical potential applied from the well contact point to the lower portion of the sub-fin reduces leakage currents from the upper portion of the fin structure.

Abstract: There is provided an electronic device and a method for its manufacture. The device comprises an elongate silicon nanowire less than 0.5 ?m in cross-sectional dimensions and having a hexagonal cross-sectional shape due to annealing-induced energy relaxation.

Abstract: FinFET transistor comprising at least: one fin that forms a channel, a source and a drain, comprising an alternating stack of first portions of silicon-rich SiGe and of second portions of a dielectric or semiconductor material, and third portions of germanium-rich SiGe arranged at least against lateral faces of the first portions, one gate that covers the channel, and wherein each one of the third portions comprises faces with a crystal orientation [111] covered by the gate.

Abstract: One illustrative method disclosed herein includes, among other things, forming a layer of insulating material in the source/drain regions of the device, wherein the layer of insulating material has an upper surface that is substantially planar with an upper surface of a gate cap layer, recessing the layer of insulating material such that its recessed upper surface exposes a surface of the fin, performing another etching process to remove at least a portion of the fin and thereby define a recessed fin trench positioned above the recessed fin, and forming an epitaxial semiconductor material that is at least partially positioned in the recessed fin trench.

Abstract: Provided is a method of fabricating a semiconductor device. The method includes forming a gate pattern on a semiconductor substrate, injecting amorphization elements into the semiconductor substrate to form an amorphous portion at a side of the gate pattern, removing the amorphous portion to form a recess region, and forming a source/drain pattern in the recess region. When the recess region is formed, an etch rate of the amorphous portion is substantially the same in two different directions (e.g., <111> and any other direction) of the semiconductor substrate.

Abstract: In one embodiment, Group III-nitride materials are used to form a semiconductor device. A fin structure is formed in the Group III-nitride material, and a gate structure, source electrodes and drain electrodes are formed in spaced relationship to the fin structure. The fin structure provides both polar and semi-polar 2DEG regions. In one embodiment, the gate structure is configured to control current flow in the polar 2DEG region. Shield conductor layers are included above the gate structure and in spaced relationship with drain regions of the semiconductor device.

Abstract: The present disclosure provides a semiconductor device and a method for manufacturing the same. The semiconductor device comprises: a semiconductor layer; a first fin being formed by patterning the semiconductor layer; and a second fin being formed by patterning the semiconductor layer, wherein: top sides of the first and second fins have the same height; bottom sides of the first and second fins adjoin the semiconductor layer; and the second fin is higher than the first fin. According to the present disclosure, a plurality of semiconductor devices with different dimensions can be integrated on the same wafer. As a result, manufacturing process can be shortened and manufacturing cost can be reduced. Furthermore, devices with different driving capabilities can be provided.

Abstract: A memory device includes a memory cell on a first region of a substrate. An active region is in a second region neighboring the first region of the substrate, and an extension direction of the active region has an acute angle with the <110> direction of the substrate. A transistor serving as a peripheral circuit is on the second region of the substrate. In the memory device, defects or failures due to a crystal defects or a dislocation of the substrate may decrease.

Abstract: Semiconductor device structures having fin structure(s) and fabrication methods thereof are presented. The methods include: providing a first mask above a substrate structure and a second mask above the first mask and the substrate structure; removing portions of the first mask not underlying the second mask and selectively etching the substrate structure using the second mask to form at least one cavity therein; providing a third mask over portions of the substrate structure not underlying the second mask and removing the second mask; and selectively etching the substrate structure using remaining portions of the first mask and the third mask to the form fin structure(s) of the semiconductor device structure, where the fin structure(s) is self-aligned with the at least one cavity in the substrate structure. For example, the semiconductor device structure can be a fin-type transistor structure, and the method can include forming a source/drain region within a cavity.

Abstract: A semiconductor structure is provided that includes a substrate comprising a first semiconductor material having a first crystallographic orientation and a first device region and a second device region. First vertically stacked and suspended nanosheets of semiconductor channel material of the first crystallographic orientation are located above the substrate and within the first device region. Second vertically stacked and suspended nanosheets of semiconductor channel material of a second crystallographic orientation are located above the substrate and within the second device region. In accordance with the present application, the second crystallographic orientation is different from the first crystallographic orientation.

Abstract: A method including forming fin spacers on opposite sidewalls of a semiconductor fin made from a semiconductor substrate, forming a dielectric layer in direct contact with the fin spacers such that a top surface of the fin and a top surface of the fin spacers remain exposed, recessing a portion of the fin between the fin spacers, removing the fin spacers to create an opening, and epitaxially growing an unmerged source drain region in the opening, where lateral growth of the unmerged source drain region is constrained on opposite sides by the dielectric layer.

Abstract: Provided are a method for fabricating a semiconductor device The method for fabricating include providing a substrate including a first region and a second region, the first region including first and second sub-regions, and the second region including third and fourth sub-regions, forming first to fourth fins on the first and second regions to protrude from the substrate, the first fin being formed on the first sub-region, the second fin being formed on the second sub-region, the third fin being formed on the third sub-region, and the fourth fin being formed on the fourth sub-region, forming first to fourth dummy gate structures to intersect the first to fourth fins, the first dummy gate structure being formed on the first fin, the second dummy gate structure being formed on the second fin, the third dummy gate structure being formed on the third fin, and the fourth dummy gate structure being formed on the fourth fin, forming a first doped region in each of the first and second fins and a second doped region

Abstract: In accordance with some embodiments, a device includes first and second p-type transistors. The first transistor includes a first channel region including a first material of a first fin. The first transistor includes first and second epitaxial source/drain regions each in a respective first recess in the first material and on opposite sides of the first channel region. The first transistor includes a first gate stack on the first channel region. The second transistor includes a second channel region including a second material of a second fin. The second material is a different material from the first material. The second transistor includes third and fourth epitaxial source/drain regions each in a respective second recess in the second material and on opposite sides of the second channel region. The second transistor includes a second gate stack on the second channel region.

Abstract: A method of forming an active device on a semiconductor wafer includes the steps of: forming a plurality of semiconductor fins on at least a portion of a semiconductor substrate; forming a dielectric layer on at least a portion of the semiconductor substrate, the dielectric layer filling gaps between adjacent fins; forming a plurality of gate structures on an upper surface of the dielectric layer; forming a channel region on the dielectric layer and under at least a portion of the gate structures, the channel region comprising a first crystalline semiconductor material; forming source and drain epitaxy regions on an upper surface of the dielectric layer and between adjacent gate structures, the source and rain regions being spaced laterally from one another; and replacing the channel region with a second crystalline semiconductor material after high-temperature processing used in fabricating the active device has been completed.

Abstract: A device includes a field effect transistor on an insulating film. A first fin extends vertically from a top side of a horizontal surface of a semiconductor substrate. An epitaxial cap rests on the first fin, with a left vertex on a left side of the epitaxial cap at a first horizontal distance from a reference line that vertically bisects the first fin, and a right vertex on the right side of the epitaxial cap at a second horizontal distance from the reference line, the first horizontal distance being at least twenty percent greater than the second horizontal distance; and a top vertex is at a third horizontal distance to the left of the reference line.

Abstract: A multi-channel self refresh device may include period generation circuit configured to output a self refresh pulse signal having a predetermined time period in response to a refresh enable signal. The multi-channel self refresh device may include a channel region configured to activate a refresh signal in response to the self refresh pulse signal, when a self refresh command signal corresponding to a channel from among a plurality of self refresh command signals is activated.

Abstract: Electrostatic discharge (ESD) devices and methods of manufacture are provided. The method includes forming a plurality of fin structures and a mesa structure from semiconductor material. The method further includes forming an epitaxial material with doped regions on the mesa structure and forming gate material over at least the plurality of fin structures. The method further includes planarizing at least the gate material such that the gate material and the epitaxial material are of a same height. The method further includes forming contacts in electrical connection with respective ones of the doped regions of the epitaxial material.

Abstract: An SRAM array and method of making is disclosed. Each SRAM cell comprises two pull-up (PU), two pass-gate (PG), and two pull-down (PD) FinFETs. The PU transistors are adjacent to each other and include one active fin having a first fin width. Each PG transistor shares at least one active fin with a PD transistor. The active fin shared by a PG and a PD transistor has a second fin width smaller than the first fin width. The method includes patterning a plurality of fins including active fins and dummy fins and patterning and removing at least a portion of the dummy fins. No dummy fin is disposed between PU FinFETs in a memory cell. One dummy fin is disposed between a PU FinFET and the at least one active fin shared by a PG and a PD transistor. At least one dummy fin is disposed between adjacent memory cells.

Abstract: A method for fabricating a fin-type field-effect transistor (FinFET) device includes forming a first fin structure over a substrate, forming a dielectric layer over the first fin structures, forming a trench with a vertical profile in the dielectric layer, depositing conformably a first semiconductor material layer over sidewalls and bottom of the trench, depositing a second semiconductor material layer over the first semiconductor material layer to filling in the remaining trench, recessing the dielectric layer to laterally expose the first semiconductor material layer and etching the exposed first semiconductor material layer to reveal the second semiconductor material layer.

Abstract: A method of manufacturing a semiconductor device is provided. The method includes forming a fin structure on a semiconductor substrate and forming a well region in the semiconductor substrate by ion implantation so as to form transistors. The transistors include a pull-up transistor, a transfer gate transistor, and a pull-down transistor of a SRAM cell. The ion implantation is used to adjust threshold voltages of the transistors. Standard threshold voltage (SVt) ion implantation conditions are used to adjust a threshold voltage of the pull-up transistor and a threshold voltage of the transfer gate transistor, and low threshold voltage (LVt) ion implantation conditions are used to adjust a threshold voltage of the pull-down transistor.

Abstract: The present invention relates generally to semiconductor devices and more particularly, to a structure and method of forming an abrupt junction in the channel regions of high density technologies, such as tight pitch FinFET devices, using recessed source-drain (S-D) regions and annealing techniques. In an embodiment, a faceted buffer layer, deposited before the S-D region is formed, may be used to control the profile and dopant concentration of the junction under the channel. In another embodiment, the profile and dopant concentration of the junction may be controlled via a dopant concentration gradient in the S-D region.

Abstract: One method disclosed includes, among other things, forming a gate structure above an active region of a semiconductor substrate, wherein a first portion of the gate structure is positioned above the active region and second portions of the gate structure are positioned above an isolation region formed in the substrate, forming a sidewall spacer adjacent opposite sides of the first portion of the gate structure so as to define first and second continuous epi formation trenches comprised of the spacer that extend for less than the axial length of the gate structure, and forming an epi semiconductor material on the active region within each of the first and second continuous epi formation trenches.

Abstract: Disclosed are various embodiments of FinFET semiconductor devices. A pair of matched capacitors can be formed that share a common source, drain and/or channel. Accordingly, the capacitance characteristics of each capacitor can be manufactured such that they are similar to one another. A resistor manufactured by employing FinFET techniques is also described. The resistor can be manufactured with an effective length that is greater than a distance traversed along a substrate by the resistor.

Abstract: A transistor device includes a gate structure disposed over a channel region of a semiconductor substrate. A source/drain recess is arranged in the semiconductor substrate alongside the gate structure. A doped silicon-germanium (SiGe) region is disposed within the source/drain recess and has a doping type which is opposite to that of the channel. An un-doped SiGe region is also disposed within the source/drain recess. The un-doped SiGe region underlies the doped SiGe region and comprises different germanium concentrations at different locations within the source/drain recess.

Abstract: A native p-type metal oxide semiconductor (PMOS) device that exhibits a low threshold voltage and a high drive current over a varying range of short channel lengths and a method for fabricating the same is discussed in the present disclosure. The source and drain regions of the native PMOS device, each include a strained region, a heavily doped raised region, and a lightly doped region. The gate region includes a stacked layer of a gate oxide having a high-k dielectric material, a metal, and a contact metal. The high drive current of the native PMOS device is primarily influenced by the increased carrier mobility due to the strained regions, the lower drain resistance due to the raised regions, and the higher gate capacitance due to the high-k gate oxide of the native PMOS device.

Abstract: Field Effect Transistors (FETs), Integrated Circuit (IC) chips including the FETs, and a method of forming the FETs and IC. FET locations and adjacent source/drain regions are defined on a semiconductor wafer, e.g., a silicon on insulator (SOI) wafer. Source/drains are formed in source/drains regions. A stopping layer is formed on source/drains. Contact spacers are formed above gates. Source/drain contacts are formed to the stopping layer, e.g., after converting the stopping layer to silicide. The contact spacers separate source/drain contacts from each other.

Abstract: A semiconductor structure is provided. The semiconductor structure includes a substrate, at least a first N-type germanium (Ge) structure and at least a first P-type Ge structure. The first N-type Ge structure is formed on the substrate and has two end parts and at least a first central part bonded between the two end parts thereof. The first central part is floated over the substrate, and a side surface of the first central part is a {111} Ge crystallographic surface. The first P-type Ge structure is formed on the substrate and has two end parts and at least a second central part bonded between the two end parts thereof. The side surface of the second central part is a {110} Ge crystallographic surface.

Abstract: A semiconductor device includes a base insulating film including silicon, an oxide semiconductor film over the base insulating film, a gate insulating film over the oxide semiconductor film, a gate electrode which is in contact with the gate insulating film and overlaps with at least the oxide semiconductor film, and a source electrode and a drain electrode electrically connected to the oxide semiconductor film. The oxide semiconductor film includes a region in which a concentration of silicon distributed from the interface with the base insulating film toward an inside of the oxide semiconductor film is lower than or equal to 1.0 at. %. A crystal portion is included at least in the region.

Abstract: A complementary metal oxide semiconductor (CMOS) device includes an n-type first transistor on a silicon substrate, the n-type first transistor including a Group III-V compound semiconductor substrate, and a p-type second transistor on the silicon substrate, the p-type second transistor including a germanium based substrate.

Abstract: An embodiment is a FinFET device. The FinFET device comprises a fin, a first source/drain region, a second source/drain region, and a channel region. The fin is raised above a substrate. The first source/drain region and the second source/drain region are in the fin. The channel region is laterally between the first and second source/drain regions. The channel region has facets that are not parallel and not perpendicular to a top surface of the substrate.

Abstract: A method for integrating a set of electronic devices on a wafer (100; 200a; 200b) of semiconductor material having a main surface includes forming a plurality of trenches extending into the wafer from the main surface. At least one layer of electrically insulating material is formed within each trench. At least one layer of electrically conductive material is formed within each trench superimposed on the at least one layer of insulating material. The formation of the plurality of trenches includes forming the trenches partitioned into sub-sets of trenches. The trenches of a first sub-set are oriented along a first common direction that is different from the orientation of the trenches of a second sub-set.

Abstract: Semiconductor devices are formed with a thin layer of fully strain relaxed epitaxial silicon germanium on a substrate. Embodiments include forming a silicon germanium (SiGe) epitaxial layer on a semiconductor substrate, implanting a dopant into the SiGe epitaxial layer, and annealing the implanted SiGe epitaxial layer.

Abstract: A semiconductor device in one embodiment includes a semiconductor substrate, a fin disposed on a surface of the semiconductor substrate, an insulator including a gate insulator disposed on a side surface of the fin, and a gate electrode disposed on the insulator that is disposed on side surfaces of the fin and an upper surface of the fin. The device further includes a plurality of epitaxial stripe shaped layers disposed horizontally on the side surface of the fin at different heights, and an interlayer dielectric disposed on the semiconductor substrate to cover the fin and applying a stress to the fin and the epitaxial layers. Any two adjacent epitaxial layers along the fin height direction determine a gap and the gaps between adjacent layers increase or decrease with increasing distance from the substrate.

Abstract: A semiconductor device includes a trench transistor cell array in a silicon semiconductor body with a first main surface and a second main surface opposite to the first main surface. A main lateral face of the semiconductor body between the first main surface and the second main surface has a first length along a first lateral direction parallel to the first and second main surfaces. The first length is equal or greater than lengths of other lateral faces of the semiconductor body. The trench transistor cell array includes predominantly linear gate trench portions. At least 50% of the linear gate trench portions extend along a second lateral direction or perpendicular to the second lateral direction. An angle between the first and second lateral directions is in a range of 45°±15°.

Abstract: An insulating layer is provided with a projecting structural body, and a channel formation region of an oxide semiconductor layer is provided in contact with the projecting structural body, whereby the channel formation region is extended in a three dimensional direction (a direction perpendicular to a substrate). Thus, it is possible to miniaturize a transistor and to extend an effective channel length of the transistor. Further, an upper end corner portion of the projecting structural body, where a top surface and a side surface of the projecting structural body intersect with each other, is curved, and the oxide semiconductor layer is formed to include a crystal having a c-axis perpendicular to the curved surface.

Abstract: A semiconductor device includes a channel having a first linear surface and a first non-linear surface. The first non-linear surface defines a first external angle of about 80 degrees to about 100 degrees and a second external angle of about 80 degrees to about 100 degrees. The semiconductor device includes a dielectric region covering the channel between a source region and a drain region. The semiconductor device includes a gate electrode covering the dielectric region between the source region and the drain region.

Abstract: A chip includes a dielectric layer having a top surface and a bottom surface, a first semiconductor layer overlying and bonded to the top surface of the dielectric layer, and a first Metal Oxide-Semiconductor (MOS) transistor of a first conductivity type. The first MOS transistor includes a first gate dielectric overlying and contacting the first semiconductor layer, and a first gate electrode overlying the first gate dielectric. A second semiconductor layer is underlying and bonded to the bottom surface of the dielectric layer. A second MOS transistor of a second conductivity type opposite to the first conductivity type includes a second gate dielectric underlying and contacting the second semiconductor layer, and a second gate electrode underlying the second gate dielectric.

Abstract: Provided are semiconductor devices and methods of manufacturing the same. The semiconductor device includes a substrate including a first top surface, a second top surface lower in level than the first top surface, and a first perpendicular surface disposed between the first and second top surfaces, a first source/drain region formed under the first top surface, a first nanowire extended from the first perpendicular surface in one direction and being spaced apart from the second top surface, a second nanowire extended from a side surface of the first nanowire in the one direction, being spaced apart from the second top surface, and including a second source/drain region, a gate electrode on the first nanowire, and a dielectric layer between the first nanowire and the gate electrode.

Abstract: An integrated circuit containing logic transistors and an array of SRAM cells in which the logic transistors are formed in semiconductor material with one crystal orientation and the SRAM cells are formed in a second semiconductor layer with another crystal orientation. A process of forming an integrated circuit containing logic transistors and an array of SRAM cells in which the logic transistors are formed in a top semiconductor layer with one crystal orientation and the SRAM cells are formed in an epitaxial semiconductor layer with another crystal orientation. A process of forming an integrated circuit containing logic transistors and an array of SRAM cells in which the SRAM cells are formed in a top semiconductor layer with one crystal orientation and the logic transistors are formed in an epitaxial semiconductor layer with another crystal orientation.

Abstract: A semiconductor device includes a gate pattern disposed on a semiconductor substrate, a bulk epitaxial pattern disposed in a recess region formed in the semiconductor substrate at a side of the gate pattern, an insert epitaxial pattern disposed on the bulk epitaxial pattern, and a capping epitaxial pattern disposed on the insert epitaxial pattern. The bulk epitaxial pattern has an upper inclined surface that is a {111} crystal plane, and the insert epitaxial pattern includes a specific element that promotes the growth rate of the insert epitaxial pattern on the upper inclined surface.

Abstract: An organic light emitting display and a method of manufacturing the same are disclosed. In one embodiment, the display includes a gate electrode formed over a substrate and an active layer electrically insulated from the gate electrode, wherein the gate electrode is closer to the substrate than the active layer. The display further includes i) a first gate insulating layer and a second gate insulating layer formed between the gate electrode and active layer so as to electrically insulate the active layer from the gate electrode and ii) source and drain electrodes each contacting the active layer.

Abstract: An efficient strain-inducing mechanism may be provided on the basis of a piezoelectric material so that performance of different transistor types may be enhanced by applying a single concept. For example, a piezoelectric material may be provided below the active region of different transistor types and may be appropriately connected to a voltage source so as to obtain a desired type of strain.

Abstract: A semiconductor device includes a trench transistor cell array in a silicon semiconductor body with a first main surface and a second main surface opposite to the first main surface. A main lateral face of the semiconductor body between the first main surface and the second main surface has a first length along a first lateral direction parallel to the first and second main surfaces. The first length is equal or greater than lengths of other lateral faces of the semiconductor body. The trench transistor cell array includes predominantly linear gate trench portions. At least 50% of the linear gate trench portions extend along a second lateral direction or perpendicular to the second lateral direction. An angle between the first and second lateral directions is in a range of 45°±15°.

Abstract: Roughly described, a method for approximating stress-induced mobility enhancement in a channel region in an integrated circuit layout, including approximating the stress at each of a plurality of sample points in the channel, converting the stress approximation at each of the sample points to a respective mobility enhancement value, and averaging the mobility enhancement values at all the sample points. The method enables integrated circuit stress analysis that takes into account stresses contributed by multiple stress generation mechanisms, stresses having vector components other than along the length of the channel, and stress contributions (including mitigations) due to the presence of other structures in the neighborhood of the channel region under study, other than the nearest STI interfaces. The method also enables stress analysis of large layout regions and even full-chip layouts, without incurring the computation costs of a full TCAD simulation.