Abstract: An integrated semiconductor device and method of manufacturing the same includes leaving one part of a semiconductor layer so that an inclined surface is formed on a trench when forming the trench on a SOI wafer. A thick silicon oxide film (second insulation film) is formed along this incline surface. This thick silicon oxide film prevents oxygen entering a boundary surface between an insulation layer and the semiconductor layer of the SOI wafer within the trench.

Abstract: Disclosed are methods and devices, among which is a device that includes a first semiconductor fin having a first gate, a second semiconductor fin adjacent the first semiconductor fin and having a second gate, and a third gate extending between the first semiconductor fin and the second semiconductor fin. In some embodiments, the third gate may not be electrically connected to the first gate or the second gate.

Abstract: A method of forming a series of spaced trenches into a substrate includes forming a plurality of spaced lines over a substrate. Anisotropically etched sidewall spacers are formed on opposing sides of the spaced lines. Individual of the lines have greater maximum width than minimum width of space between immediately adjacent of the spacers between immediately adjacent of the lines. The spaced lines are removed to form a series of alternating first and second mask openings between the spacers. The first mask openings are located where the spaced lines were located and are wider than the second mask openings. Alternating first and second trenches are simultaneously etched into the substrate through the alternating first and second mask openings, respectively, to form the first trenches to be wider and deeper within the substrate than are the second trenches. Other implementations and embodiments are disclosed.

Abstract: A process for forming a zeolite beta dielectric layer onto a substrate such as a silicon wafer has been developed. The zeolite beta is characterized in that it has an aluminum concentration from about 0.1 to about 2.0 wt. %, and has crystallites from about 5 to about 40 nanometers. The process involves first dealuminating a starting zeolite beta, then preparing a slurry of the dealuminated zeolite beta followed by coating a substrate, e.g. silicon wafer with the slurry, heating to form a zeolite beta film and treating the zeolite beta with a silylating agent.

Abstract: A method for manufacturing a semiconductor device includes forming a semiconductor substrate to have a SOI structure by an epitaxial process for forming a gate while forming an insulating film pattern in a bottom where a device isolation trench is formed. The method thereby increases the process margin for forming a device isolation film and prevents the punch-through phenomenon to improve electrical characteristics of semiconductor devices and increase product yield.

Abstract: A method of forming an integrated circuit structure includes providing a semiconductor substrate; forming a first isolation region in the semiconductor substrate; after the step of forming the first isolation region, forming a metal-oxide-semiconductor (MOS) device at a surface of the semiconductor substrate, wherein the step of forming the MOS device comprises forming a source/drain region; and after the step of forming the MOS device, forming a second isolation region in the semiconductor substrate.

Abstract: Methods of forming isolation structures are disclosed. A method of forming isolation structures for an image sensor array of one aspect may include forming a dielectric layer over a semiconductor substrate. Narrow, tall dielectric isolation structures may be formed from the dielectric layer. The narrow, tall dielectric isolation structures may have a width that is no more than 0.3 micrometers and a height that is at least 1.5 micrometers. A semiconductor material may be epitaxially grown around the narrow, tall dielectric isolation structures. Other methods and apparatus are also disclosed.

Abstract: This invention is to provide a semiconductor device having a reduced variation in the transistor characteristics. The semiconductor device has a SOI substrate, a first element isolation insulating layer, first and second conductivity type transistors, and first and second back gate contacts. The SOI substrate has a semiconductor substrate having first and second conductivity type layers, an insulating layer, and a semiconductor layer. The first element isolation insulating layer is buried in the SOI substrate, has a lower end reaching the first conductivity type layer, and isolates a first element region from a second element region. The first and second conductivity type transistors are located in the first and second element regions, respectively, and have respective channel regions formed in the semiconductor layer. The first and second back gate contacts are coupled to the second conductivity type layers in the first and second element regions, respectively.

Abstract: A system and method for forming an isolation trench is provided. An embodiment comprises forming a trench and then lining the trench with a dielectric liner. Prior to etching the dielectric liner, an outgassing process is utilized to remove any residual precursor material that may be left over from the deposition of the dielectric liner. After the outgassing process, the dielectric liner may be etched, and the trench may be filled with a dielectric material.

Abstract: A semiconductor device includes: a SOI substrate including a support layer, a first insulation film and a SOI layer; a first circuit; a second circuit; and a trench separation element. The SOI substrate further includes a first region and a second region. The first region has the support layer, the first insulation film and the SOI layer, which are stacked in this order, and the second region has only the support layer. The trench separation element penetrates the support layer, the first insulation film and the SOI layer. The trench separation element separates the first region and the second region. The first circuit is disposed in the SOI layer of the first region. The second circuit is disposed in the support layer of the second region.

Abstract: The formation of a gap-filling silicon oxide layer with reduced volume fraction of voids is described. The deposition involves the formation of an oxygen-rich less-flowable liner layer before an oxygen-poor more-flowable gapfill layer. However, the liner layer is deposited within the same chamber as the gapfill layer. The liner layer and the gapfill layer may both be formed by combining a radical component with an unexcited silicon-containing precursor (i.e. not directly excited by application of plasma power). The liner layer has more oxygen content than the gapfill layer and deposits more conformally. The deposition rate of the gapfill layer may be increased by the presence of the liner layer. The gapfill layer may contain silicon, oxygen and nitrogen and be converted at elevated temperature to contain more oxygen and less nitrogen. The presence of the gapfill liner provides a source of oxygen underneath the gapfill layer to augment the gas phase oxygen introduced during the conversion.

Abstract: A semiconductor structure is provided, comprising: a Si substrate; a porous structure layer formed on the Si substrate, in which the porous structure layer has a flat surface and comprises a Si1-xGex layer with low Ge content; and a Ge-containing layer formed on the porous structure layer, in which the Ge-containing layer comprises a Ge layer or a Si1-yGey layer with high Ge content and x?y. Further, a method for forming the semiconductor structure is also provided.

Abstract: A method for fabricating a nonvolatile memory device includes forming a substrate structure having a tunnel dielectric layer and a floating-gate conductive layer formed over an active region defined by a first isolation layer forming a first inter-gate dielectric layer and a first control-gate conductive layer over the substrate structure, forming a trench by etching the first control-gate conductive layer, the first inter-gate dielectric layer, the floating-gate conductive layer, the tunnel dielectric layer, and the active region to a given depth, forming a second isolation layer to fill the trench; and forming a second control-gate conductive layer over the resultant structure having the second isolation layer formed therein.

Abstract: A semiconductor device and a method for forming the same are disclosed. In a method for forming the semiconductor substrate including a cell region and a peripheral region, a guard pattern defined by an epitaxial growth layer located at the edge part between the cell region and the peripheral region is formed. As the guard pattern is not damaged by an oxidation process, a bias leakage path between an N-well bias and a P-well bias of the peripheral region is prevented from occurring Reliability of a gate oxide film may be increased, resulting in an increased production yield of the semiconductor device and implementation of stable voltage and current characteristics.

Abstract: A vertically arranged laterally diffused metal-oxide-semiconductor (LDMOS) device comprises a trench extending into a semiconductor body toward a semiconductor substrate. The trench includes sidewalls, a bottom portion connecting the sidewalls, a dielectric material lining the trench and a diffusion agent layer lining the dielectric material. A lightly doped drain region adjoins the trench and extends laterally around the sidewalls from the diffusion agent layer into the semiconductor body. In one embodiment, a method for fabricating a vertically arranged LDMOS device comprises forming a trench extending into a semiconductor body toward a semiconductor substrate, the trench including sidewalls, a bottom portion connecting the sidewalls, a dielectric material lining the trench and a diffusion agent layer lining the dielectric material.

Abstract: A semiconductor structure and method of manufacturing the semiconductor structure, and more particularly to a semiconductor structure having reduced metal line resistance and a method of manufacturing the same in back end of line (BEOL) processes. The method includes forming a first trench extending to a lower metal layer Mx+1 and forming a second trench remote from the first trench. The method further includes filling the first trench and the second trench with conductive material. The conductive material in the second trench forms a vertical wiring line extending orthogonally and in electrical contact with an upper wiring layer and electrically isolated from lower metal layers including the lower metal layer Mx+1. The vertical wiring line decreases a resistance of a structure.

Abstract: A method and circuits for implementing a temporary disable function at indeterminate times of circuitry to be protected in a semiconductor chip, such as in an integrated circuit or a system on a chip (SOC) by modulating threshold voltage shifts of a timing sensitive circuit, and a design structure on which the subject circuit resides are provided. The timing sensitive circuit is designed to be sensitive to threshold-voltage shifts and is placed over an independently voltage controlled silicon region. Upon startup, the independently voltage controlled silicon region is grounded, and then is left floating. Each time a hack attempt or predefined functional oddity is detected, charge is applied onto the independently voltage controlled silicon region. After a defined charge has accumulated, the device threshold voltages in the timing sensitive circuit above the independently voltage controlled silicon region are modulated causing the timing-sensitive circuit to fail.

Abstract: A semiconductor chip has an independently voltage controlled silicon region that is a circuit element useful for controlling capacitor values of eDRAM trench capacitors and threshold voltages of field effect transistors overlying the independently voltage controlled silicon region. A bottom, or floor, of the independently voltage controlled silicon region is a deep implant of opposite doping to a doping of a substrate of the independently voltage controlled silicon region. A top, or ceiling, of the independently voltage controlled silicon region is a buried oxide implant in the substrate. Sides of the independently voltage controlled silicon region are deep trench isolation. Voltage of the independently voltage controlled silicon region is applied through a contact structure formed through the buried oxide.

Abstract: System and method for reducing contact resistance and improving barrier properties is provided. An embodiment includes a dielectric layer and contacts extending through the dielectric layer to connect to conductive regions. A contact barrier layer is formed between the conductive regions and the contacts by electroless plating the conductive regions after openings have been formed through the dielectric layer for the contact. The contact barrier layer is then treated to fill the grain boundary of the contact barrier layer, thereby improving the contact resistance. In another embodiment, the contact barrier layer is formed on the conductive regions by electroless plating prior to the formation of the dielectric layer.

Abstract: A field effect transistor (FET) that includes a drain formed in a first plane, a source formed in the first plane, a channel formed in the first plane and between the drain and the source and a gate formed in the first plane. The gate is separated from at least a portion of the body by an air gap. The air gap is also in the first plane.

Abstract: A method of unifying device performance within an integrated circuit die includes providing a layout of an integrated circuit die with multiple functional circuit blocks; filling a field between the multiple functional circuit blocks with dummy diffusion patterns; and filling the field between the multiple functional circuit blocks with dummy gate patterns such that the dummy gate patterns and the dummy diffusion patterns are completely overlapped.

Abstract: A semiconductor device including a first conduction type semiconductor layer; a second conduction type element forming region formed above the first conduction type semiconductor layer and formed with at least one semiconductor element formed on a surface region of the second conduction type element forming region; a first conduction type element-isolation region insulating and segregating the second conduction type element forming region from the exterior; and a second conduction type buried region formed at the interface of the first conduction type semiconductor layer and the second conduction type element forming region, formed separated from the first conduction type element-isolation region. In the semiconductor device a second conduction type high concentration region is buried in the surface of the second conduction type element forming region and formed to surround the semiconductor element and separated from the first conduction type element-isolation region.

Abstract: A method for producing an encapsulation module and/or for encapsulating a micromechanical arrangement, wherein electronic connection provisions are formed from a blank of electrically conductive semiconductor material, by one or more structuring processes and/or etching processes, wherein, in the course of forming the electronic connection provisions, a pedestal of the semiconductor material arises, on which the electronic connection provisions are arranged, wherein the latter are subsequently embedded with an embedding material and the embedding material and/or the semiconductor pedestal are removed after the embedding to an extent such that a defined number of the electronic connection provisions have electrical contacts on at least one of the outer surfaces of the encapsulation module thus produced, wherein upon forming the electronic connection provisions, on the pedestal of the semiconductor material, an insular material hump is formed, on which a plated-through hole is arranged in each case, and which e

Abstract: A suite of novel structures and methods is provided to reduce power consumption in a wide array of electronic devices and systems. Some of these structures and methods can be implemented largely by reusing existing bulk CMOS process flows and manufacturing technology, allowing the semiconductor industry as well as the broader electronics industry to avoid a costly and risky switch to alternative technologies. As will be discussed, some of the structures and methods relate to a Deeply Depleted Channel (DDC) design, allowing CMOS based devices to have a reduced ?VT compared to conventional bulk CMOS and can allow the threshold voltage VT of FETs having dopants in the channel region to be set much more precisely. The DDC design also can have a strong body effect compared to conventional bulk CMOS transistors, which can allow for significant dynamic control of power consumption in DDC transistors.

Abstract: Various systems and methods related to semiconductor devices having a plurality of layers and having a first conductive trace on a first layer electrically connected to a second conductive trace on a second layer and electrically isolated from a third electrical trace on the second layer are provided. A semiconductor structure can include first, second and third layers. The first conducting layer may be etched to form a first trench for the first conductive trace. A layer of material on the second layer in the first trench can define a patch area, wherein the patch area is disposed in a location where the first trench crosses over the third electrical trace. A second trench may be etched in an area defined by the first trench and the patch area to remove material in the second layer exposed by the first trench, leaving material of the layer under the patch area.

Abstract: Disclosed is a semiconductor structure for producing a handle wafer contact in trench insulated SOI discs which may be used as a deep contact (7, 6, 30?) to the handle wafer (1) of a thick SOI disc as well as for a trench insulation (40). Therein, the same method steps are used for both structures which are used as deep contact to the handle wafer of the thick SOI disc as well as trench insulation.

Abstract: A method for forming a semiconductor device includes forming a nanotube region using a thin epitaxial layer formed on the sidewall of a trench in the semiconductor body. The thin epitaxial layer has uniform doping concentration. In another embodiment, a first thin epitaxial layer of the same conductivity type as the semiconductor body is formed on the sidewall of a trench in the semiconductor body and a second thin epitaxial layer of the opposite conductivity type is formed on the first epitaxial layer. The first and second epitaxial layers have uniform doping concentration. The thickness and doping concentrations of the first and second epitaxial layers and the semiconductor body are selected to achieve charge balance. In one embodiment, the semiconductor body is a lightly doped P-type substrate. A vertical trench MOSFET, an IGBT, a Schottky diode and a P-N junction diode can be formed using the same N-Epi/P-Epi nanotube structure.

Abstract: The invention relates to a semiconductor structures and methods of manufacture and, more particularly, to a dual contact trench resistor in shallow trench isolation (STI) and methods of manufacture. In a first aspect of the invention, a method comprises forming a trench in a substrate; forming a first insulator layer within the trench; forming a first electrode within the trench, on the first insulator layer, and isolated from the substrate by the first insulator layer; forming a second insulator layer within the trench and on the first electrode; and forming a second electrode within the trench, on the second insulator layer, and isolated from the substrate by the first insulator layer and the second insulator layer.

Abstract: When forming sophisticated high-k metal gate electrode structures on the basis of a replacement gate approach, superior process uniformity may be achieved by implementing at least one planarization process after the deposition of the placeholder material, such as the polysilicon material, and prior to actually patterning the gate electrode structures.

Abstract: The embodiments described provide mechanisms for doping oxide in the STIs with carbon to make etch rate in the narrow and wide structures equal and also to make corners of wide STIs strong. Such carbon doping can be performed by ion beam (ion implant) or by plasma doping. The hard mask layer can be used to protect the silicon underneath from doping. By using the doping mechanism, the even surface topography of silicon and STI enables patterning of gate structures and ILD0 gapfill for advanced processing technology.

Abstract: A semiconductor integrated circuit device includes a semiconductor substrate; a dummy pattern extending in one direction on the semiconductor substrate; a junction region electrically connecting the dummy pattern to the semiconductor substrate; and a voltage applying unit that is configured to apply a bias voltage to the dummy pattern.

Abstract: A semiconductor device and a method for manufacturing the same are disclosed. The semiconductor device includes a substrate having a first conductor-type, a buried layer of a second conductor-type on the substrate, a drain, and a first guard-ring on one side of the drain, a second guard-ring on one side of the first guard-ring, and a third guard-ring on one side of the second guard-ring.

Abstract: A superjunction semiconductor device is provided having at least one column of a first conductivity type and at least one column of a second conductivity type extending from a first main surface of a semiconductor substrate toward a second main surface of the semiconductor substrate opposed to the first main surface. The at least one column of the second conductivity type has a first sidewall surface proximate the at least one column of the first conductivity type and a second sidewall surface opposed to the first sidewall surface. A termination structure is proximate the second sidewall surface of the at least one column of the second conductivity type. The termination structure includes a layer of dielectric of an effective thickness and consumes about 0% of the surface area of the first main surface. Methods for manufacturing superjunction semiconductor devices and for preventing surface breakdown are also provided.

Abstract: A high power amplifier used for a front end module of a cellular telephone is a silicon-based CMOS integrated circuit. The output stage of the amplifier includes an LDMOSFET portion in which many LDMOSFET cells are integrated. In the LDMOSFET cell, to reduce the resistance between a backside source electrode and a surface source region, a polysilicon plug doped with boron in a high concentration is embedded into a semiconductor substrate. The polysilicon plug contracts due to solid phase epitaxial growth caused by a heat treatment to generate strain in the silicon substrate. The manufacturing method of a semiconductor device such as an LDMOSFET includes forming a hole passing through an epitaxial layer from the surface of a substrate and embedding a polysilicon plug. A polysilicon member is deposited out in a state where a thin silicon oxide film exists on the inner surface of the hole.

Abstract: A semiconductor device includes a first well formed in a predetermined region of a semiconductor substrate, a second well formed in a predetermined region in the first well, and a third well formed in the first well with the third well being spaced apart from the second well at a predetermined distance. A multiple well of the semiconductor substrate, the first well, the second well, the first well, and the third well, which are sequentially disposed, is formed. Accordingly, a breakdown voltage can be increased and a leakage current can be reduced. It is therefore possible to prevent the drop of an erase voltage and to reduce the error of an erase operation.

Abstract: A method of manufacturing an electronic device, comprising a layer of semiconductive material and at least one insulative feature arranged to interrupt the layer of semiconductive material, comprises: providing a layer of semiconductive material, and a layer of compressible material supporting the layer of semiconductive material; and forming the or each insulative feature by a method comprising displacing a respective selected portion of the layer of semiconductive material towards the compressible material so as to compress compressible material under the or each displaced portion and separate at least partly the or each displaced portion from undisplaced semiconductive material.

Abstract: A silicon-on-insulator (SOI) structure is provided for forming through vias in a silicon wafer carrier structure without backside lithography. The SOI structure includes the silicon wafer carrier structure bonded to a silicon substrate structure with a layer of buried oxide and a layer of nitride separating these silicon structures. Vias are formed in the silicon carrier structure and through the oxide layer to the nitride layer and the walls of the via are passivated. The vias are filled with a filler material of either polysilicon or a conductive material. The substrate structure is then etched back to the nitride layer and the nitride layer is etched back to the filler material. Where the filler material is polysilicon, the polysilicon is etched away forming an open via to the top surface of the carrier wafer structure. The via is then backfilled with conductive material.

Abstract: A device may comprise a flexure formed of a first semiconductor material. A first trench may be formed in the flexure. The first trench may separate the first semiconductor material into a first portion and a second portion thereof. An oxide layer may be formed in the first trench. The oxide layer may extend over a top portion of the first semiconductor material. A second semiconductor material may be formed on the oxide layer. The first trench and the oxide layer may cooperate to electrically isolate the first portion and the second portion from one another.

Abstract: An electronic device may have a MEMS device formed of a first conductive material. A trench may be formed in the MEMS device. A layer of non-conductive material may be formed in the trench. A second conductive material may be formed upon the non-conductive material.

Abstract: A method of forming shallow trench isolation (STI) structures using a multi-step etch process is disclosed. The first etch step is performed by selectively etching the substrate at a substantially higher etching rate than the mask layer to form preliminary openings having steep taper angles. The second etch step is performed by non-selectively etching the substrate to deepen the preliminary openings to form STI gaps with substantially flat bottoms.

Abstract: A semiconductor component with straight insulation trenches formed in a semiconductor material providing semiconductor areas laterally insulated from each other. Each insulation trench has a uniform width along its longitudinal direction represented by a central line. The semiconductor component has an intersecting area into which at least three of the straight insulation trenches lead. A center of the intersecting area is defined as a point of intersection of the continuations of the center lines. A central semiconductor area disposed in the intersecting area is connected with one of the semiconductor areas and contains the center of the intersecting area.

Abstract: A semiconductor device, and method of manufacturing the device, having a p type diffusion layer; a V-groove including a bottom surface parallel to the rear surface and exposing the p type diffusion layer and a tapered side surface rising from the bottom surface; a p type semiconductor layer on the rear surface surrounded by the tapered side surface of the V-groove; and a p type isolation layer formed on the side surface and electrically connecting the p type diffusion layer on the front surface and the p type semiconductor layer on the rear surface. The V-groove has a chamfered configuration around the intersection between a corner part of the side surface and the bottom surface of the V-groove. An object is to prevent performance degradation due to stress concentration at the corner part of a recessed part caused by thermal history in soldering.

Abstract: A semiconductor device including reentrant isolation structures and a method for making such a device. A preferred embodiment comprises a substrate of semiconductor material forming at least one isolation structure having a reentrant profile and isolating one or more adjacent operational components. The reentrant profile of the at least one isolation structure is formed of substrate material and is created by ion implantation, preferably using oxygen ions applied at a number of different angles and energy levels. In another embodiment the present invention is a method of forming an isolation structure for a semiconductor device performing at least one oxygen ion implantation.

Abstract: The present invention discloses an LDMOS device structure, including a MOS transistor cell, wherein an isolation region is formed on each outer side of both a source region and a drain region of the MOS transistor cell; each isolation region includes a plurality of isolation trenches and isolates the MOS transistor cell from its surroundings; the height of the isolation region is smaller than that of a gate of the MOS transistor cell. The present invention also discloses a manufacturing method of the LDMOS device structure, including forming isolation trenches by lithography and etching processes, then forming isolation regions of SiO2 by depleting silicon between isolation trenches through high-temperature drive-in. The present invention can reduce parasitic capacitance, surface unevenness and difficulty of subsequent process and realize the production of small-size gate devices by forming a thicker field oxide layer and a gap structure of isolation trenches.

Abstract: A fabrication method for a semiconductor device structure is provided. The device structure has a layer of silicon and a layer of silicon dioxide overlying the layer of silicon, and the method begins by forming an isolation recess by removing a portion of the silicon dioxide and a portion of the silicon. The isolation recess is filled with stress-inducing silicon nitride and, thereafter, the silicon dioxide is removed such that the stress-inducing silicon nitride protrudes above the silicon. Next, the exposed silicon is thermally oxidized to form silicon dioxide hardmask material overlying the silicon. Thereafter, a first portion of the silicon dioxide hardmask material is removed to reveal an accessible surface of the silicon, while leaving a second portion of the silicon dioxide hardmask material intact. Next, silicon germanium is epitaxially grown from the accessible surface of the silicon.

Abstract: A method for manufacturing a semiconductor device comprises: etching a semiconductor substrate to form a trench that defines an active region of a line type; burying an insulating film in the trench; and removing a portion of the active region of a line type to form a separated active region. The method improves the process for forming an active region using a Spacer patterning Technology (SPT), thereby preventing characteristic defects of the device and improving the operating characteristic.

Abstract: A multiple gate field effect transistor and a planar field effect transistor formed in the same substrate each have a top planar surface underneath each corresponding gate that are co-planar with one another and also co-planar with a top surface of a shallow trench isolation region located therebetween. The relatively older planar FET fabrication technology has added to it the relatively newer MUGFET fabrication technology without disruption to the planar fabrication technology and with relatively little added cost.

Abstract: A silicon-on-insulator device has a localized biasing structure formed in the insulator layer of the SOI. The localized biasing structure includes a patterned conductor that provides a biasing signal to distinct regions of the silicon layer of the SOI. The conductor is recessed into the insulator layer to provide a substantially planar interface with the silicon layer. The conductor is connected to a bias voltage source. In an embodiment, a plurality of conductor is provided that respectively connected to a plurality of voltage sources. Thus, different regions of the silicon layer are biased by different bias signals.

Abstract: A semiconductor device includes groove-like regions that are formed between two adjacent bit lines among a plurality of bit lines each having upper and side surfaces covered with a cap insulating film and a side-wall insulating film, respectively, a SiON film that contains more O (oxygen) than N (nitrogen) and continuously covers inner surfaces of the groove-like regions, and a silicon dioxide film formed by reforming polysilazane and filled in the groove-like regions with the SiON film interposed therebetween.

Abstract: A method for fabricating a device isolation structure of a semiconductor device includes the steps of forming a pad oxide layer and a pad nitride layer over a semiconductor substrate including a cell region and a dummy region, etching a portion of the pad nitride layer, the pad oxide layer and the semiconductor substrate to form a trench, forming a sidewall oxide layer over the sidewalls of the trench; removing the sidewall oxide layer in the dummy region, forming a silicon nitride layer over the sidewalls of the sidewall oxide layer both in the cell region and in the dummy region, filling the trench with an insulating layer, polishing the insulating layer to expose the pad nitride layer, and removing the pad nitride layer.