Abstract: A semiconductor element of this invention includes a drift layer of a first conductivity type formed on a semiconductor substrate of the first conductivity type, a well layer of a second conductivity type selectively formed in the surface of the drift layer, a source layer of the first conductivity type selectively formed in the surface of the well layer, a trench formed to reach at least the inside of the drift layer from the surface of the source layer through the well layer, a buried electrode formed in the trench through a first insulating film, and a control electrode formed on the drift layer, the well layer, and the source layer through a second insulating film.

Abstract: Provided is an insulated gate semiconductor device. In the device, source regions are provided in the entire operation area and a first back gate region is provided below the source region between trenches. Moreover, a second back gate region connected to the first back gate region is provided outside of the source regions. Thereafter, a first electrode layer coming into contact with the source regions is provided in the entire operation area, and a second electrode layer coming into contact with the second back gate regions is provided around the first electrode layer. Accordingly, potentials can be individually applied to the first electrode layer and the second electrode layer. Thus, it is possible to perform control for preventing reverse flow caused by a parasitic diode.

Abstract: A nonvolatile semiconductor memory device includes a plurality of pillars protruding upward from a semiconductor substrate and having respective top surfaces and opposing sidewalls, a bit line on the top surfaces of the pillars and connecting a row of the pillars along a first direction, a pair of word lines on the opposing sidewalls of one of the plurality of pillars and crossing beneath the bit line, and a pair of memory layers interposed between respective ones of the pair of word lines and the one of the plurality of pillars. Methods of fabricating a nonvolatile semiconductor memory device include selectively etching a semiconductor substrate to form pluralities of stripes having opposing sidewalls and being arranged along a direction, forming memory layers and word lines along the sidewalls of the stripes selectively etching the stripes to form a plurality of pillars, and forming a bit line connecting the pillars and crossing above the word lines.

Abstract: Self-aligned recessed gate structures and method of formation are disclosed. Field oxide areas for isolation are first formed in a semiconductor substrate. A plurality of columns are defined in an insulating layer formed over the semiconductor substrate subsequent to which a thin sacrificial oxide layer is formed over exposed regions of the semiconductor substrate but not over the field oxide areas. A dielectric material is then provided on sidewalls of each column and over portions of the sacrificial oxide layer and of the field oxide areas. A first etch is conducted to form a first set of trenches within the semiconductor substrate and a plurality of recesses within the field oxide areas. A second etch is conducted to remove dielectric residue remaining on the sidewalls of the columns and to form a second set of trenches. Polysilicon is then deposited within the second set of trenches and within the recesses to form recessed conductive gates.

Abstract: A gate electrode is buried in a trench passing through a second conductivity type first body region formed on a first conductivity type drain region so as to form a recessed portion at the upper part of the trench. An insulating film is formed on the gate electrode so as to occupy the recessed portion partway. A first conductivity type source region is formed in at least a region of the upper part of the first body region which serves as at least the wall part of the trench. A second conductivity type second body region is formed in the other region of the upper part thereof so as to be adjacent to the source region in the direction that the trench extends. A second conductivity type third body region is formed in the respective upper parts of the source region and the second body region.

Abstract: A FET includes a trench in a semiconductor region. The trench has a lower portion with a shield electrode therein, and an upper portion with a gate electrode therein, where the upper portion is wider than the lower portion. The semiconductor region includes a substrate of a first conductivity type and a first silicon region of a second conductivity type over the substrate. The first silicon region has a first portion extending to a depth intermediate top and bottom surfaces of the gate electrode. The first silicon region has a second portion extending to a depth intermediate top and bottom surfaces of the shield electrode. The semiconductor region further includes a second silicon region of the first conductivity type between the lower trench portion and the second portion of the first silicon region that has a laterally-graded doping concentration decreasing in a direction away from the sidewalls of the lower trench portion.

Abstract: A shielded gate field effect transistor includes a trench extending into a semiconductor region. A shield electrode is in a lower portion of the trench, and is insulated from the semiconductor region by a shield dielectric. The shield dielectric comprises first and second dielectric layers, the first dielectric layer extending between the second dielectric layer and the semiconductor region. The second dielectric layer comprises a material which during oxidation process inhibits growth of oxide along surfaces of the semiconductor region covered by the second dielectric layer. An inter-electrode dielectric overlies the shield electrode, and a gate dielectric lines upper trench sidewalls. A gate electrode is in an upper portion of the trench over the inter-electrode dielectric.

Abstract: By forming an implantation mask prior to the definition of the drain and the source areas, an effective decoupling of the gate dopant concentration from that of the drain and source concentrations is achieved. Moreover, after removal of the implantation mask, the lateral dimension of the gate electrode may be defined by well-established sidewall spacer techniques, thereby providing a scaling advantage with respect to conventional approaches based on photolithography and anisotropic etching.

Abstract: According to some embodiments of the invention, transistors have channel regions between channel-portion holes. Methods of forming the same include at least two channel-portion holes disposed in a semiconductor substrate. Line patterns are formed in parallel to be spaced apart from each other on a main surface of the semiconductor substrate to fill the channel-portion holes. A channel region is disposed in the semiconductor substrate below the line patterns. At this time, the channel region is formed between the channel-portion holes and also covers lower portions of the channel-portion holes. Driving current capability and refresh characteristics of DRAMs utilizing the inventive transistors are improved.

Abstract: An accumulation mode FET (ACCUFET) which includes an insulated gate, an adjacently disposed insulated source field electrode, and a source contact that makes Schottky contact with the base region of the ACCUFET.

Abstract: A semiconductor device is provided with a main electrode of main switching elements region, a sensor electrode of sensor switching elements region, and a protective device formed between the main electrode and the sensor electrode. The protective device electrically connects the main electrode and the sensor electrode when a predetermined potential difference is produced between the main electrode and the sensor electrode. The semiconductor device can handle excessive voltage such as ESD generated between the sensor electrode and the gate electrode while simultaneously preventing gate drive loss from increasing.

Abstract: A U-shape Metal-Oxide-Semiconductor (UMOS) device comprises a P-base layer, an N+ source region disposed in the P-base layer where the source region has a first surface coplanar with a first surface of the P-base layer, a dielectric layer extending through the P-base layer and forming a U-shape trench having side walls and floor enclosing a trench interior region, a conducting gate material filling the trench interior region, a first accumulation channel layer disposed along a first side wall of the U-shape trench and in contact with the source region and a first side wall of the U-shape trench, a P-junction gate disposed adjacent to the dielectric layer floor and in proximity to the first accumulation channel layer, and an N-drift region where the P-junction gate is disposed between the dielectric layer and the N-drift region.

Abstract: An access transistor arrangement is provided for a 6F2 stacked capacitor DRAM memory cell layout with shared bit line contacts. The access transistors are arranged in pairs along semiconductor lines. The two transistors of each pair of transistors are arranged laterally reversed opposing the respective common bit line section. Each pair of access transistors is separated from the adjacent pair of access transistors by an isolation transistor which is permanently turned off. The access transistors and the isolation transistors are formed as identical recessed channel transistors with elongated channel and enhanced isolation properties. The same dopant concentration may be provided for both junctions of the access transistors. As identical devices are provided both as access transistor and as isolation transistors, the complexity of lithographic patterning processes is reduced.

Abstract: According to one embodiment of the present invention, a method of forming an apparatus comprises forming a plurality of deep trenches and a plurality of shallow trenches in a first region of a substrate. At least one of the shallow trenches is positioned between two deep trenches. The plurality of shallow trenches and the plurality of deep trenches are parallel to each other. The method further comprises depositing a layer of conductive material over the first region and a second region of the substrate. The method further comprises etching the layer of conductive material to define a plurality of lines separated by a plurality of gaps over the first region of the substrate, and a plurality of active device elements over the second region of the substrate. The method further comprises masking the second region of the substrate.

Abstract: The invention is intended to present an insulated gate type semiconductor device that can be manufactured easily and its manufacturing method while realizing both higher withstand voltage design and lower on-resistance design. The semiconductor device comprises N+ source region 31, N+ drain region 11, P? body region 41, and N? drift region 12. By excavating part of the upper side of the semiconductor device, a gate trench 21 is formed. The gate trench 21 incorporates the gate electrode 22. A P floating region 51 is provided beneath the gate trench 21. A further trench 35 differing in depth from the gate trench 21 may be formed, a P floating region 54 being provided beneath the trench 25.

Abstract: A high withstand voltage transistor includes: a gate electrode provided in a trench formed on a semiconductor substrate; a source and a drain which are respectively formed on a side of the gate electrode and another side of the gate electrode, and which are a predetermined distance away from the gate electrode; first electric field relaxation layers one of which is formed on a wall of the trench on the side of the source and another one of which is formed on a wall of the trench on the side of the drain; and second electric field relaxation layers one of which is formed between the source and the gate electrode, and another one of which is formed between the drain and the gate electrode.

Abstract: A trench transistor structure having a field electrode arrangement formed in trenches is disclosed. In one embodiment, the field electrode arrangement is conductively connected to subvoltage taps of a voltage divider for the purpose of stabilizing the potentials on a longer time scale than dynamic charge reversal processes.

Abstract: A method for fabricating a vertical channel transistor device is provided. An opening is formed in a dielectric stack comprised of a pad nitride layer and a pad oxide layer. A plurality of epitaxial silicon growth and dry etching processes are carried out to form drain, vertical channel and source in the opening. Subsequently, sidewall gate dielectric and sidewall gate electrode are formed on the vertical channel. The present invention is suited for dynamic random access memory (DRAM) devices, particularly suited for very high-density trench-capacitor DRAM devices.

Abstract: A semiconductor device provided with: a channel region formed in a surface of a semiconductor substrate in a predetermined depth range, a trench being formed in the surface as penetrating the channel region in a depthwise direction; a gate insulating film formed on an inside wall of the trench, the gate insulating film being in contact with the channel region; and a gate electrode including: a polysilicon layer opposing the channel region with the gate insulating film interposed therebetween, the polysilicon layer being embedded in an internal space of the trench at least in the predetermined depth range; and a low-resistance layer essentially formed from a metal element and disposed in the trench above the polysilicon layer that opposes the channel region.

Abstract: A top drain MOSgated device has its drain on the top of semiconductor die and its source on the bottom of the die substrate. Parallel spaced trenches extend from the die top surface through a drift region, a channel region and terminate on the substrate region. The bottoms of each trench receive a silicide conductor to short the substrate source to channel regions. The silicide conductors are then insulated at their top surfaces and gate electrodes are placed in the same trenches as those receiving the channel/source short.

Abstract: The present invention provides a semiconductor device comprising: a dual-gate peripheral transistor having a transistor structure of surface channel nMOSFET and a transistor structure of surface channel pMOSFET; and a cell transistor having an nMOSFET structure with a recess channel structure, a gate electrode of the cell transistor having an N-type polysilicon layer which contains of N-type impurities at an approximately constant concentration.

Abstract: An integrated circuit and method of forming an integrated circuit is disclosed. One embodiment includes a FinFET of a first type having a first gate electrode and a FinFET of a second type having a second gate electrode. The first gate electrode is formed in a gate groove that is defined in a semiconductor substrate and a bottom side of a portion of the second gate electrode is disposed above a main surface of the semiconductor substrate.

Abstract: This invention discloses a semiconductor power device that includes a plurality of power transistor cells surrounded by a trench opened in a semiconductor substrate. At least one active cell further includes a trenched source contact opened between the trenches wherein the trenched source contact opened through a source region into a body region for electrically connecting the source region to a source metal disposed on top of an insulation layer wherein a trench bottom surface of the trenched source contact further covered with a conductive material to function as an integrated Schottky barrier diode in said active cell. A shielding structure is disposed at the bottom and insulated from the trenched gate to provide shielding effect for both the trenched gate and the Schottky diode.

Abstract: A method of manufacturing a semiconductor device. In the method, a thin film is formed on an Si substrate having face orientation (100), that part of the thin film, which lies on an element-isolating region, is removed. Then, the Si substrate is subjected to selective etching, making a trench in the substrate to isolate an element, by using the thin film as mask and a mixture solution of hydrofluoric acid and ozone water.

Abstract: The layout density of the through electrodes in the horizontal plane of the substrate is enhanced. Through holes 103 extending through the silicon substrate 101 is provided. An insulating film 105 is buried within the through hole 103. A plurality of columnar through plugs 107 are provided in the insulating film 105.

Abstract: The dense accumulation of hole carriers can be obtained over a wide range of a semiconductor region in a floating state formed within a body region of an IGBT. An n type semiconductor region (52) whose potential is floating is formed within a p? type body region (28). The n type semiconductor region (52) is isolated from an n+ type emitter region (32) and an n? type drift region (26) by the body region (28). Furthermore, a second electrode (62) is formed, so as to oppose to at least a part of the semiconductor region (52) via an insulator film (64). The second electrode (62) does not oppose to the emitter region (32).

Abstract: Disclosed herein are a recess-gate structure in which junctions have a thickness significantly smaller than the thickness of a device isolation layer to thereby prevent shorting of the junctions located at opposite lateral sides of the device isolation layer close thereto, resulting in an improvement in the operational reliability of a resultant device, and a method for forming the same. The recess-gate structure comprises a silicon substrate in which an active region and a device isolation region are defined, a plurality of gates formed on the substrate, gate spacers formed at the side wall of the respective gates, and junctions formed in the substrate at opposite lateral sides of the gates and defining an asymmetrical structure relative to each other. A gate recess is defined in the active region of the substrate to have a stepped profile consisting of a bottom plane, top plane, and vertical plane.

Abstract: A power semiconductor device which includes gate liners extending along gate insulation liners and an insulation block spacing the two gate liners.

Abstract: According to some embodiments, a structure of vertical transistor includes gate electrodes distanced by a predetermined interval in an active region, formed in a vertical shape to have a predetermined depth from a top surface of a semiconductor substrate. A gate insulation layer is formed between one side wall of the gate electrode and the substrate. A gate spacer is formed in another sidewall of the gate electrode, covering the gate electrode. A contact plug is formed between the gate spacer. A plug impurity layer is formed in a lower part of the contact plug, and source and drain are formed opposite to the gate electrode within the active region. Thereby, an area occupied by a gate electrode is substantially reduced, so a unit memory cell has a 4F2 structure, reducing a memory cell size, by forming a vertical-type gate electrode within an active region.

Abstract: A CMOS image sensor includes a first conductive type semiconductor substrate defined by a photodiode area and a transistor area, a trench formed in the semiconductor substrate corresponding to a transfer transistor of the transistor area, a gate electrode of the transfer transistor, formed in the trench, a second conductive type impurity ion area formed in the semiconductor substrate of the photodiode area, and a first conductive type impurity ion area formed on a surface of the second conductive type impurity ion area.

Abstract: A trench FET has source contacts which contact the entire top surface of source regions, and contact a portion of side walls of the source regions. The side walls of the source regions form a portion of the side walls of the trenches in the trench FET.

Abstract: According to one exemplary embodiment, a method includes forming first, second, and third shallow trench isolation regions in a substrate, wherein the second shallow trench isolation region is situated between the first and the third shallow trench isolation regions. The second shallow trench isolation region is removed to form a transistor channel trench. A substantially U-shaped gate is formed in the transistor channel trench. According to another embodiment, a transistor includes a substrate, and first and second shallow trench isolation regions in the substrate. A substantially U-shaped gate is formed in the substrate between said first and second shallow trench isolation regions.

Abstract: In accordance with an embodiment of the present invention, a FET is formed as follows. An exposed surface area of a silicon layer where silicon can be removed is defined. A portion of the silicon layer is removed to form a middle section of a trench extending into the silicon layer from the exposed surface area of the silicon layer. Additional exposed surface areas of the silicon layer where silicon can be removed are defined. Additional portions of the silicon layer are removed to form outer sections of the trench such that the outer sections of the trench extend into the silicon layer from the additional exposed surface areas of the silicon layer. The middle section of the trench extends deeper into the silicon layer than the outer sections of the trench.

Abstract: A field effect transistor is formed as follows. A semiconductor region of a first conductivity type with an epitaxial layer of a second conductivity extending over the semiconductor region is provided. A trench extending through the epitaxial layer and terminating in the semiconductor region is formed. A two-pass angled implant of dopants of the first conductivity type is carried out to thereby form a region of first conductivity type along the trench sidewalls. A threshold voltage adjust implant of dopants of the second conductivity type is carried out to thereby convert a conductivity type of a portion of the region of first conductivity type extending along upper sidewalls of the trench to the second conductivity type. Source regions of the first conductivity type flanking each side of the trench are formed.

Abstract: A method of fabricating an MOS device is described. A substrate doped a first type dopant is provided as a drain. A first type epitaxial layer is formed on the substrate and is patterned with a trench to form several islands. A gate dielectric layer is than formed on the surface of the trench, and a gate is formed in the trench covering the gate dielectric layer. A second type dopant is doped into the islandswith the doping concentration decreasing gradually from the bottom to the top of the islands. Afterwards, a source is formed at the top of the islands. Accordingly, the doping concentration in the islands decreases gradually from the drain to the sourcewith the highest doping concentration near the drain. Therefore, the width of the depletion region can be reduced, and the length of the device channel can be reduced for lowering channel resistance and gate capacitance.

Abstract: A field effect transistor (FET) includes a trench extending into a silicon region of a first conductive type. A shield insulated from the silicon region by a shield dielectric extends in a lower portion of the trench. A gate electrode is in the trench over but insulated from the shield electrode by an inter-poly dielectric (IPD). The IPD comprises a conformal layer of dielectric and a thermal oxide layer.

Abstract: In an embodiment, a 3-dimensional flash memory device includes: a gate extending in a vertical direction on a semiconductor substrate; a charge storing layer surrounding the gate; a silicon layer surrounding the charge storing layer; a channel region vertically formed in the silicon layer; and source/drain regions vertically formed on both sides of the channel region in the silicon layer. Integration can be improved by storing data in a 3-dimensional manner; a 2-bit operation can be performed by providing transistors on both sides of the gate.

Abstract: A plurality of mesas are formed in the substrate. Each pair of mesas forms a trench. A plurality of diffusion areas are formed in the substrate. A mesa diffusion area is formed in each mesa top and a trench diffusion area is formed under each trench. A vertical, non-volatile memory cell is formed on each sidewall of the trench. Each memory cell includes a fixed threshold element located vertically between a pair of non-volatile gate insulator stacks. In one embodiment, each gate insulator stack includes a tunnel insulator formed over the sidewall, a deep trapping layer, and a charge blocking layer. In another embodiment, an injector silicon rich nitride layer is formed between the deep trapping layer and the charge blocking layer.

Abstract: The invention relates to a vertical field-effect transistor in source-down structure, in which the active zones (10, 7, 11) are introduced from trenches (5, 8, 9) into a semiconductor body (1), a source electrode (18) being connected via the filling (6) of a body trench (5) to a highly doped substrate (2) via a conductive connection (15).

Abstract: A low resistance buried back contact for SOI devices. A trench is etched in an insulating layer at minimum lithographic dimension, and sidewalls are deposited in the trench to decrease its width to sublithographic dimension. Conducting material is deposited in the trench, which serves as a low-resistance contact to the back side of the device. In another embodiment, the trench-fill material is separated from the device by an insulating layer, and serves as a back gate structure.

Abstract: Fabrication of recessed channel array transistors (RCAT) with a corner gate device includes forming pockets between a semiconductor fin that includes a gate groove and neighboring shallow trench isolations that extend along longs sides of the semiconductor fin. A protection liner covers the semiconductor fin and the trench isolations in a bottom portion of the gate groove and the pockets. An insulator collar is formed in the exposed upper sections of the gate groove and the pockets, wherein a lower edge of the insulator collar corresponds to a lower edge of source/drain regions formed within the semiconductor fin. The protection liner is removed. The bottom portion of the gate groove and the pockets are covered with a gate dielectric and a buried gate conductor layer. The protection liner avoids residuals of polycrystalline silicon between the active area in the semiconductor fin and the insulator collar.

Abstract: A semiconductor device having high withstand voltage is provided. An active groove 22a includes a long and narrow main groove part 26 and a sub groove part 27 connected to a longitudinal side surface of the main groove part, and a buried region 24 of a second conductivity type whose height is lower than the bottom surface of the base diffusion region 32a of the second conductivity type is provided on the bottom surface of the main groove part 26. An active groove filling region 25 of the second conductivity type in contact with the base diffusion region 32a is provided in the sub groove part 27. The buried region 24 is contacted to the base diffusion region 32a through the active groove filling region 25. Since one gate groove 83 is formed by the part above the buried region 24 in one active groove 22a, the gate electrode plugs 48 are not separated, which allows the electrode pattern to be simplified.

Abstract: A semiconductor apparatus includes a semiconductor substrate of a first conductivity type, a base region of a second conductivity type formed on a principal surface of the semiconductor substrate, a trench formed in a periphery of the base region, and an endless source region of the first conductivity type formed on a surface of the base region along the trench. In this semiconductor apparatus, the principal planes on side surfaces of the trench are composed of planes [100] and [110]. The interior angle of intersection of adjacent side surfaces of the trench is 135°. A minimum distance between the base region and the plane [110] facing each other through the source region is shorter than a minimum distance between the base region and the plane [100] facing each other through the source region.

Abstract: A first main electrode is provided on one surface thereof. On the other surface thereof, a second semiconductor layer of the first conduction type and a third semiconductor layer of the second conduction type are arranged alternately along the surface. A fourth semiconductor layer of the second conduction type and a fifth semiconductor layer of the first conduction type are stacked on the surfaces of the second and third semiconductor layers. The semiconductor device further comprises a control electrode formed in a trench with an insulator interposed therebetween. The trench passes through the fourth and fifth semiconductor layers and reaches the second semiconductor layer. A sixth semiconductor layer of the first conduction type is diffused from the bottom of the trench. A second main electrode is connected to the fourth and fifth semiconductor layers.

Abstract: The invention relates to a vertical transistor and an oxidation process that achieves a substantially curvilinear recess bottom. The recess serves as the gate receptacle that may facilitate a more uniform gate oxide layer. One embodiment relates to a storage cell that is disposed in the recess along with an electrode. Another embodiment relates to a system that includes the vertical transistor or the vertical storage cell.

Abstract: A semiconductor power device includes a substrate of a first conductivity type and an epitaxial layer of the first conductivity type over and in contact with the substrate. A first trench extends into and terminates within the epitaxial layer. A sinker trench extends from the top surface of the epitaxial layer through the epitaxial layer and terminates within the substrate. The sinker trench is laterally spaced from the first trench, and is wider and extends deeper than the first trench. The sinker trench is lined with an insulator only along the sinker trench sidewalls so that a conductive material filling the sinker trench makes electrical contact with the substrate along the bottom of the trench and makes electrical contact with an interconnect layer along the top of the trench.

Abstract: According to some embodiments of the invention, there is provided recessed transistors without semiconductor substrate fences formed on the sidewalls of a device isolation layer and methods of forming the same. The recessed transistors and methods provide a way of removing the fences of the semiconductor substrate from the sidewalls of the device isolation layer to increase the effective width of a channel region. The recessed transistors and methods include forming the device isolation layer on the semiconductor substrate to isolate an active region. Further, a channel-portion hole is formed in the active region so that the sidewall height of the channel-portion hole is greater in a width direction of the active region than in a length direction thereof. A gate pattern may further be formed across the active region such that it fills the channel-portion hole.

Abstract: MOSFET devices suitable for operation at gate lengths less than about 40 nm, and methods of their fabrication is being presented. The MOSFET devices include a ground plane formed of a monocrystalline Si based material. A Si based body layer is epitaxially disposed over the ground plane. The body layer is doped with impurities of opposite type than the ground plane. The gate has a metal with a mid-gap workfunction directly contacting a gate insulator layer. The gate is patterned to a length of less than about 40 nm, and possibly less than 20 nm. The source and the drain of the MOSFET are doped with the same type of dopant as the body layer. In CMOS embodiments of the invention the metal in the gate of the NMOS and the PMOS devices may be the same metal.

Abstract: Vertical channel semiconductor devices include a semiconductor substrate with a pillar having an upper surface. An insulated gate electrode is around a periphery of the pillar. The insulated gate electrode has an upper surface at a vertical level lower than the upper surface of the pillar to vertically space apart the insulated gate electrode from the upper surface of the pillar. A first source/drain region is in the substrate adjacent the pillar. A second source/drain region is disposed in an upper region of the pillar including the upper surface of the pillar. A contact pad contacts the entire upper surface of the pillar to electrically connect to the second source/drain region.

Abstract: A semiconductor device includes a body region, a drift region having a first part and a second part, and a trench gate electrode. The body region is disposed on the drift region. The first and second parts extend in an extending direction so that the second part is adjacent to the first part. The trench gate electrode penetrates the body region and reaches the drift region so that the trench gate electrode faces the body region and the drift region through an insulation layer. The trench gate electrode extends in a direction crossing with the extending direction of the first and second parts. The first part includes a portion near the trench gate electrode, which has an impurity concentration equal to or lower than that of the body region.