Abstract: A semiconductor device which solves the following problem of a super junction structure: due to a relatively high concentration in the body cell region (active region), in peripheral areas (peripheral regions or junction end regions), it is difficult to achieve a breakdown voltage equivalent to or higher than in the cell region through a conventional junction edge terminal structure or resurf structure. The semiconductor device includes a power MOSFET having a super junction structure formed in the cell region by a trench fill technique. Also, super junction structures having orientations parallel to the sides of the cell region are provided in a drift region around the cell region.

Abstract: A semiconductor device includes a doped layer which contains a first dopant of a first conductivity type. In the doped layer, a counter-doped zone is formed in an edge area that surrounds an element area of the semiconductor device. The counter-doped zone contains at least the first dopant and a second dopant of a second conductivity type, which is the opposite of the first conductivity type. A concentration of the second dopant is at least 20% and at most 100% of a concentration of the first dopant. The dopants in the counter-doped zone decrease charge carrier mobility and minority carrier lifetime such that the dynamic robustness of the semiconductor device is increased.

Abstract: A super-junction semiconductor substrate is configured in such a manner that an n-type semiconductor layer of a parallel pn structure is opposed to a boundary region between an active area and a peripheral breakdown-resistant structure area. A high-concentration region is formed at the center between p-type semiconductor layers that are located on both sides of the above n-type semiconductor layer. A region where a source electrode is in contact with a channel layer is formed over the n-type semiconductor layer. A portion where the high-concentration region is in contact with the channel layer functions as a diode. The breakdown voltage of the diode is set lower than that of the device.

Abstract: Provided is a semiconductor device in which on-resistance is largely reduced based on a new principle of operation. In the semiconductor device, if an embedded electrode is at negative potential, a depletion layer is formed from a trench to a neighboring trench so that a channel is turned off. If the embedded electrode is at a positive potential, the depletion layer is not formed in every region between the neighboring trenches so that the channel is turned on.

Abstract: A shielded gate transistor device may include one or more shield electrodes formed in a semiconductor substrate at a first level and one or more gate electrodes formed in the semiconductor substrate at a second level that is different from the first level. One or more portions of the one or more gate electrodes overlap one or more portions of the one or more shield electrodes. At least a portion of the gate electrodes is oriented non-parallel to the one or more shield electrodes. The shield electrodes are electrically insulated from the semiconductor substrate and the one or more gate electrodes are electrically insulated from the substrate and shield electrodes.

Abstract: Disclosed is a semiconductor device whose breakdown voltage is made high by controlling local concentration of an electric field. A source region faces a second plane, one of side faces of a groove part, and a part thereof extends in a direction in parallel to a nodal line of first and second planes. A drift region faces a third plane being the other side face of the groove part opposite to the second plane with a part thereof extending in a direction parallel to the nodal line of the first plane and the third plane, and is formed at a lower concentration than the source region. The drain region is provided so as to be placed on the other side of the drift region opposite to the groove part and so as to touch the drift region, and is formed at a higher concentration than the drift region.

Abstract: A switching element is provided having a semiconductor substrate. A trench gate electrode is formed in the upper surface of the semiconductor substrate. An n-type first semiconductor region, a p-type second semiconductor region, and an n-type third semiconductor region are formed in a region in contact with a gate insulating film in the semiconductor substrate. At a position below the second semiconductor region, there is formed a p-type fourth semiconductor region connected to the second semiconductor region and opposing the gate insulating film via the third semiconductor region and containing boron. A high-concentration-carbon containing region having a carbon concentration higher than that of a semiconductor region exposed on the lower surface of the semiconductor substrate is formed in at least a part of the portion of the third semiconductor region, positioned between the fourth semiconductor region and the gate insulating film, that is in contact with the fourth semiconductor region.

Abstract: A power semiconductor device that realizes high-speed turnoff and soft switching at the same time has an n-type main semiconductor layer that includes lightly doped n-type semiconductor layers and extremely lightly doped n-type semiconductor layers arranged alternately and repeatedly between a p-type channel layer and an n+-type field stop layer, in a direction parallel to the first major surface of the n-type main semiconductor layer. A substrate used for manufacturing the semiconductor device is fabricated by forming trenches in an n-type main semiconductor layer 1 and performing ion implantation and subsequent heat treatment to form an n+-type field stop layer in the bottom of the trenches. The trenches are then filled with a semiconductor doped more lightly than the n-type main semiconductor layer for forming extremely lightly doped n-type semiconductor layers. The manufacturing method is applicable with variations to various power semiconductor devices such as IGBT's, MOSFET's and PIN diodes.

Abstract: In one embodiment, a vertical HVFET includes a pillar of semiconductor material a pillar of semiconductor material arranged in a loop layout having at least two substantially parallel and substantially linear fillet sections each having a first width, and at least two rounded sections, the rounded sections having a second width narrower than the first width, a source region of a first conductivity type being disposed at or near a top surface of the pillar, and a body region of a second conductivity type being disposed in the pillar beneath the source region. First and second dielectric regions are respectively disposed on opposite sides of the pillar, the first dielectric region being laterally surrounded by the pillar, and the second dielectric region laterally surrounding the pillar. First and second field plates are respectively disposed in the first and second dielectric regions.

Abstract: A power semiconductor device of the present invention has an active region and an electric field reduction region and includes: an emitter region of a first conductivity type; a base region of a second conductivity type in contact with the emitter region; an electrical strength providing region of the first conductivity type in contact with the base region; a collector region of the second conductivity type in contact with the electrical strength providing region; and a collector electrode in contact with the collector region; wherein the collector region is disposed on both a active region and a electric field reduction region each containing a dopant of the second conductivity type, and the collector region disposed on the electric field reduction region includes a region having a lower density of carriers of the second conductivity type than the collector region disposed on the active region.

Abstract: A field effect transistor includes a plurality of trenches extending into a semiconductor region of a first conductivity type. The plurality of trenches includes a plurality of gated trenches and a plurality of non-gated trenches. A body region of a second conductivity extends in the semiconductor region between adjacent trenches. A dielectric material fills a bottom portion of each of the gated and non-gated trenches. A gate electrode is disposed in each gated trench. A conductive material of the second conductivity type is disposed in each non-gated trench such that the conductive material and contacts corresponding body regions along sidewalls of the non-gated trench.

Abstract: A superjunction semiconductor device is disclosed which has, in the active section, a first alternating-conductivity-type layer which makes a current flow in the ON-state of the device and sustains a bias voltage in the OFF-state of the device. There is a second alternating-conductivity-type layer in a edge-termination section surrounding the active section. The width of a region of a second conductivity type in the second alternating-conductivity-type layer becomes narrower at a predetermined rate from the edge on the active section side toward the edge of the edge termination section. The superjunction semiconductor device facilitates manufacturing the edge-termination section which exhibits a high breakdown voltage and a high reliability for breakdown voltage through a process that exhibits a high mass-productivity.

Abstract: Power devices which include trench Schottky barrier diodes and also (preferably) trench-gate transistors. Isolation trenches flank both the gate regions and the diode mesas, and have an additional diffusion below the bottom of the isolation trenches. The additional diffusion helps to reduce the electric field (and leakage), when the device is in the OFF state, at both the Schottky barrier and at the body diode.

Abstract: Vertical capacitive depletion field effect transistors (VCDFETs) and methods for fabricating VCDFETs are disclosed. An example VCDFET includes one or more interleaved drift and gate regions. The gate region(s) may be configured to capacitively deplete the drift region(s) though one or more insulators that separate the gate region(s) from the drift region(s). The drift region(s) may have graded/non-uniform doping profiles. In addition, one or more ohmic and/or Schottky contacts may be configured to couple one or more source electrodes to the drift region(s).

Abstract: A semiconductor device has a semiconductor substrate having an upper main surface and a lower main surface. The semiconductor substrate includes a drain layer, a main base region, an underpad base region and a source region. The semiconductor device includes a first main electrode connected to the main base regions and the source region and not connected to the underpad base region, a gate electrode opposed to a channel region in the main base region interposed between the drain layer and the source region with a gate insulating film provided therebetween, a conductive gate pad opposed to an exposed surface of the underpad base region in the upper main surface with an insulating layer interposed therebetween and the conductive gate pad is connected to the gate electrode, and a second main electrode connected to the lower main surface.

Abstract: Recessed access transistor devices used with semiconductor devices may include gate electrodes having materials with multiple work functions, materials that are electrically isolated from each other and supplied with two or more voltage supplies, or materials that create a diode junction within the gate electrode.

Abstract: Methods for fabricating an electronic device and electronic devices therefrom are provided. A method includes forming one or more masking layers on a semiconducting surface of a substrate and forming a plurality of dielectric isolation features and a plurality of fin-type projections using the masking layer. The method also includes processing the masking layers and the plurality of fin-type projections to provide an inverted T-shaped cross-section for the plurality of fin-type projections that includes a distal extension portion and a proximal base portion. The method further includes forming a plurality of bottom gate layers on the distal extension portion and forming a plurality of control gate layers on the plurality of dielectric isolation features and the plurality of bottom gate layers.

Abstract: Power devices, and related process, where both gate and field plate trenches have multiple stepped widths, using self-aligned process steps.

Abstract: According to one embodiment, a power semiconductor device includes a second semiconductor layer of a first conductivity type and a third semiconductor layer of a second conductivity type periodically disposed repeatedly along a surface of the first semiconductor layer on a first semiconductor layer of the first conductivity type. A first main electrode is provided to electrically connect to the first semiconductor layer. A fourth semiconductor layer of the second conductivity type is provided to connect to the third semiconductor layer. Fifth semiconductor layers of the first conductivity type are selectively provided in the fourth semiconductor layer surface. A second main electrode is provided on a surface of the fourth and fifth semiconductor layers. A control electrode is provided on a surface of the fourth, fifth, and second semiconductor layers via a gate insulating film. First insulating films are provided by filling a trench made in the second semiconductor layer.

Abstract: A trench MOSFET comprising source regions having a doping profile of a Gaussian-distribution along the top surface of epitaxial layer and floating dummy cells formed between edge trench and active area is disclosed. A SBR of n region existing at cell corners renders the parasitic bipolar transistor difficult to turn on, and the floating dummy cells having no parasitic bipolar transistor act as buffer cells to absorb avalanche energy when gate bias is increasing for turning on channel, therefore, the UIS failure issue is avoided and the avalanche capability of the trench MOSFET is enhanced.

Abstract: A Vertical Multiple Implanted Silicon Carbide Power MOSFET (VMIMOSFET) includes a first conductivity semiconductor substrate, a first conductivity semiconductor drift layer on the top of the substrate, a multitude of second conductivity layers implanted in the drift layer. The body layer is where the channel is formed. A first conductivity source layer is interspaced appropriately inside of the second conductivity layers. A gate oxide of a certain thickness and another oxide of a different thickness, a greater thickness than the gate oxide, placed in between the body layers but in such way that its shape does not distort the gate oxide in the channel. A charge compensated body layer of the second conductivity formed outside of the channel region and only at specific high electric field locations in the structure. The device and the manufacturing method deliver a power SiC MOSFET with increased frequency of operation and reduced switching losses.

Abstract: Semiconductor device structures and related fabrication methods are provided. An exemplary semiconductor device structure includes a first vertical drift region of semiconductor material, a second vertical drift region of semiconductor material, and a buried lateral drift region of semiconductor material that abuts the vertical drift regions. In one or more embodiments, the vertical drift regions and buried lateral drift region have the same conductivity type, wherein a body region of the opposite conductivity type overlies the buried lateral drift region between the vertical drift regions.

Abstract: A gate trench 13 is formed in a semiconductor substrate 10. The gate trench 13 is provided with a gate electrode 16 formed over a gate insulating film 14. A portion of the gate electrode 16 protrudes from the semiconductor substrate 10, and a sidewall 24 is formed over a side wall portion of the protruding portion. A body trench 25 is formed in alignment with an adjacent gate electrode 16. A cobalt silicide film 28 is formed over a surface of the gate electrode 16 and over a surface of the body trench 25. A plug 34 is formed using an SAC technique.

Abstract: A semiconductor component having a semiconductor body is disclosed. In one embodiment, the semiconductor component includes a drift zone of a first conductivity type, a drift control zone composed of a semiconductor material which is arranged adjacent to the drift zone at least in places, a dielectric which is arranged between the drift zone and the drift control zone at least in places. A quotient of the net dopant charge of the drift control zone, in an area adjacent to the accumulation dielectric and the drift zone, divided by the area of the dielectric arranged between the drift control zone and the drift zone is less than the breakdown charge of the semiconductor material in the drift control zone.

Abstract: In various embodiments, a semiconductor device is provided. The semiconductor device may include a first source/drain region, a second source/drain region, an active region electrically coupled between the first source/drain region and the second source/drain region, a trench disposed between the second source/drain region and at least a portion of the active region, a first isolation layer disposed over the bottom and the sidewalls of the trench, electrically conductive material disposed over the isolation layer in the trench, a second isolation layer disposed over the active region, and a gate region disposed over the second isolation layer. The electrically conductive material may be coupled to an electrical contact.

Abstract: A method of forming a device is disclosed. A substrate defined with a device region is provided. A gate having an upper and a lower portion is formed in a trench in the substrate in the device region. The upper portion forms a gate electrode and the lower portion forms a gate field plate. First and second surface doped regions are formed adjacent to the gate. The gate field plate introduces vertical reduced surface (RESURF) effect in a drift region of the device.

Abstract: A circuit is proposed for limiting maximum switching FET drain-source voltage (VDS) of a transformer-coupled push pull power converter with maximum DC supply voltage VIN—MAX. Maximum VDS is accentuated by leakage inductances of the push pull transformer and the power converter circuit traces. The limiting circuit bridges the drains of the switching FETs and it includes two serially connected opposing Zener diodes each having a Zener voltage Vzx. The invention is applicable to both N-channel and P-channel FETs. In a specific embodiment, Vzx is selected to be slightly ?2*VIN—MAX with the maximum VDS clamped to about VIN—MAX+½Vzx. In another embodiment, a proposed power switching device with integrated VDS-clamping includes a switching FET; and a Zener diode having a first terminal and a second terminal, the second terminal of the Zener diode is connected to the drain terminal of the switching FET.

Abstract: A MOSFET power chip includes a first vertical MOSFET and a second vertical MOSFET. The first vertical MOSFET includes a semiconductor body having a first surface defining a source and a second surface defining a drain and a gate structure formed in the semiconductor body near the second surface. A via is formed within the semiconductor body and is substantially perpendicular to the first surface and the second surface. The via has a first end electrically coupled to the first surface and a second end electrically coupled to the gate structure. The second vertical MOSFET includes a semiconductor body having a first surface defining a source, a second surface defining a drain and a gate structure formed in the semiconductor body near the first surface.

Abstract: A semiconductor device is provided. The semiconductor device includes a semiconductor body and a source metallization which is arranged on the semiconductor body. The semiconductor body includes in a cross-section a drift region of a first conductivity type, a first body region of a second conductivity type which adjoins the drift region, a first compensation region of the second conductivity type which adjoins the first body region, has a lower maximum doping concentration than the first body region and forms a first pn-junction with the drift region, and a first charge trap. The first charge trap adjoins the first compensation region and includes a field plate and an insulating region which adjoins the drift region and partly surrounds the field plate. The source metallization is arranged in resistive electric connection with the first body region. Further, a method for producing a semiconductor device is provided.

Abstract: A method of manufacturing a semiconductor device includes providing a semiconductor layer of a first conductivity type and forming a semiconductor layer of a second conductivity type thereon. The method also includes forming an insulator layer on the semiconductor layer of the second conductivity type, etching a trench into at least the semiconductor layer of the second conductivity type, and forming a thermal oxide layer in the trench and on the semiconductor layer of the second conductivity type. The method further includes implanting ions into the thermal oxide layer, forming a second insulator layer, removing the second insulator layer from a portion of the trench, and forming an oxide layer in the trench and on the epitaxial layer. Moreover, the method includes forming a material in the trench, forming a second gate oxide layer over the material, and patterning the second gate oxide layer.

Abstract: According to one embodiment, a power semiconductor device includes a first semiconductor layer of a first conductivity type, a second semiconductor layer of the first conductivity type and a third semiconductor layer of a second conductivity type, a fourth semiconductor layer, a fifth semiconductor layer, a first and second main electrode, a first and second insulating film and a control electrode. The second and third layers are provided periodically on the first layer. The fourth layer is provided on the third layer. The fifth layer is selectively provided on the fourth layer. The first film is provided on sidewalls of a trench that reaches from a surface of the fifth layer to the second layer. The second film is provided closer to a bottom side of the trench than the first film and has a higher permittivity than the first film. The control electrode is embedded in the trench.

Abstract: A field effect transistor includes a plurality of trenches extending into a semiconductor region of a first conductivity type. The plurality of trenches includes a plurality of gated trenches and a plurality of non-gated trenches. A body region of a second conductivity extends in the semiconductor region between adjacent trenches. A dielectric material fills a bottom portion of each of the gated and non-gated trenches. A gate electrode is disposed in each gated trench. A conductive material of the second conductivity type is disposed in each non-gated trench such that the conductive material and contacts corresponding body regions along sidewalls of the non-gated trench.

Abstract: A capacitor structure for a pumping circuit includes a substrate, a U-shaped bottom electrode in the substrate, a T-shaped top electrode in the substrate and a dielectric layer disposed between the U-shaped bottom and T-shaped top electrode. The contact area of the capacitor structure between the U-shaped bottom and T-shaped top electrode is extended by means of the cubic engagement of the U-shaped bottom electrode and the T-shaped top electrode.

Abstract: A super-junction trench MOSFET is disclosed for high voltage device by applying a first doped column region of first conductivity type between a pair of second doped column regions of second conductivity type adjacent to sidewalls of a pair of deep trenches with buried voids in each unit cell for super-junction. Meanwhile, at least one trenched gate and multiple trenched source-body contacts are formed in each unit cell between the pair of deep trenches.

Abstract: This invention discloses a semiconductor power device formed in a semiconductor substrate comprises a highly doped region near a top surface of the semiconductor substrate on top of a lightly doped region. The semiconductor power device further comprises a body region, a source region and a gate disposed near the top surface of the semiconductor substrate and a drain disposed at a bottom surface of the semiconductor substrate. The semiconductor power device further comprises source trenches opened into the highly doped region filled with a conductive trench filling material in electrical contact with the source region near the top surface. The semiconductor power device further comprises a buried field ring regions disposed below the source trenches and doped with dopants of opposite conductivity from the highly doped region.

Abstract: Exemplary power semiconductor devices with features providing increased breakdown voltage and other benefits are disclosed.

Abstract: A power semiconductor device that includes a buried source electrode disposed at the bottom of a trench below a respective gate electrode, and a source connector including a finger electrically connecting the buried source to the source contact of the device, and a process for fabricating the device.

Abstract: A super-junction trench MOSEET is disclosed for high voltage device by applying a first doped column region of first conductivity type between a pair of second doped column regions of second conductivity type adjacent to sidewalls of a pair of deep trenches in each unit cell for super-junction. Meanwhile, at least one trenched gate and multiple trenched source-body contacts are formed in each unit cell between the pair of deep trenches.

Abstract: The present invention discloses a high voltage device and a manufacturing method thereof. The high voltage device is formed in a first conductive type substrate. A low voltage device is also formed in the substrate. The high voltage device includes a drift region, a gate, a source, a drain, and a mitigation region. The mitigation region has a second conductive type, and is formed in the drift region between the gate and drain. The mitigation region is formed by a process step which also forms a lightly doped drain (LDD) region in the low voltage device.

Abstract: A semiconductor arrangement includes a semiconductor body and a power transistor arranged in a first device region of the semiconductor body. The power transistor includes at least one source region, a drain region, and at least one body region, at least one drift region of a first doping type and at least one compensation region of a second doping complementary to the first doping type, and a gate electrode arranged adjacent to the at least one body region and dielectrically insulated from the body region by a gate dielectric. The semiconductor arrangement also includes a further semiconductor device arranged in a second device region of the semiconductor body. The second device region includes a well-like structure of the second doping type surrounding a first semiconductor region of the first doping type. The further semiconductor device includes device regions arranged in the first semiconductor region.

Abstract: A semiconductor component having differently structured cell regions, and a method for producing it. For this purpose, the semiconductor component includes a semiconductor body. A first electrode on the top side of the semiconductor body is electrically connected to a first zone near the surface of the semiconductor body. A second electrode is electrically connected to a second zone of the semiconductor body. Furthermore, the semiconductor body has a drift path region, which is arranged in the semiconductor body between the first electrode and the second electrode. A cell region of the semiconductor component is subdivided into a main cell region and an auxiliary cell region, wherein the breakdown voltage of the auxiliary cells is greater than the breakdown voltage of the main cells.

Abstract: A schottky diode, a resistive memory device including the schottky diode and a method of manufacturing the same. The resistive memory device includes a semiconductor substrate including a word line, a schottky diode formed on the word line, and a storage layer formed on the schottky diode. The schottky diode includes a first semiconductor layer, a conductive layer formed on the first semiconductor layer and having a lower work function than the first semiconductor layer, and a second semiconductor layer formed on the to conductive layer.

Abstract: A semiconductor device includes a semiconductor body having a first surface defining a vertical direction and a source metallization arranged on the first surface. In a vertical cross-section the semiconductor body further includes: a drift region of a first conductivity type; at least two compensation regions of a second conductivity type each of which forms a pn-junction with the drift region and is in low resistive electric connection with the source metallization; a drain region of the first conductivity type having a maximum doping concentration higher than a maximum doping concentration of the drift region, and a third semiconductor layer of the first conductivity type arranged between the drift region and the drain region and includes at least one of a floating field plate and a floating semiconductor region of the second conductivity type forming a pn-junction with the third semiconductor layer.

Abstract: A power transistor includes a plurality of transistor cells. Each transistor cell has a first electrode coupled to a first electrode interconnection region overlying a first major surface, a control electrode coupled to a control electrode interconnection region overlying the first major surface, and a second electrode coupled to a second electrode interconnection region overlying a second major surface. Each transistor cell has an approximately constant doping concentration in the channel region. A dielectric platform is used as an edge termination of an epitaxial layer to maintain substantially planar equipotential lines therein. The power transistor finds particular utility in radio frequency applications operating at a frequency greater than 500 megahertz and dissipating more than 5 watts of power. The semiconductor die and package are designed so that the power transistor can efficiently operate under such severe conditions.

Abstract: A method of forming an accumulation-mode field effect transistor includes forming a channel region of a first conductivity type in a semiconductor region of the first conductivity type. The channel region may extend from a top surface of the semiconductor region to a first depth within the semiconductor region. The method also includes forming gate trenches in the semiconductor region. The gate trenches may extend from the top surface of the semiconductor region to a second depth within the semiconductor region below the first depth. The method also includes forming a first plurality of silicon regions of a second conductivity type in the semiconductor region such that the first plurality of silicon regions form P-N junctions with the channel region along vertical walls of the first plurality of silicon regions.

Abstract: In one embodiment, the invention comprises a MOSFET comprising individual MOSFET cells. Each cell comprises a U-shaped well (P type) and two parallel sources (N type) formed within the well. A Number of source rungs (doped N) connect sources at multiple locations. Regions between two rungs comprise a body (P type). These features are formed on an N-type epitaxial layer, which is formed on an N-type substrate. A contact extends across and contacts a number of source rungs and bodies. Gate oxide and a gate contact overlie a leg of a first well and a leg of a second adjacent well, inverting the conductivity responsive to a gate voltage. A MOSFET comprises a plurality of these cells to attain a desired low channel resistance. The cell regions are formed using self-alignment techniques at several states of the fabrication process.

Abstract: This document discusses, among other things, a semiconductor device including first and second conductive layers, the first conductive layer including a gate runner and a drain contact and the second conductive layer including a drain conductor, at least a portion of the drain conductor overlying at least a portion of the gate runner. A first surface of the semiconductor device can include a gate pad coupled to the gate runner and a drain pad coupled to the drain contact and the drain conductor.

Abstract: A semiconductor device includes a source, a drain, and a gate configured to selectively enable a current to pass between the source and the drain. The semiconductor device includes a drift zone between the source and the drain and a first field plate adjacent the drift zone. The semiconductor device includes a dielectric layer electrically isolating the first field plate from the drift zone and charges within the dielectric layer close to an interface of the dielectric layer adjacent the drift zone.

Abstract: This document discusses, among other things, a semiconductor device including a first metal layer coupled to a source region and a second metal layer coupled to a gate structure, wherein at least a portion of the first and second metal layers overlap vertically.

Abstract: A semiconductor device with a super-junction structure is provided, including: a semiconductor substrate having a first conductivity type; an epitaxial layer having the first conductivity type formed over the semiconductor substrate; a first doping region having the first conductive type formed in a portion of the epitaxial layer; a second doping region having a second conductivity type formed in a portion of the of the epitaxial layer; a third doping region having the second conductivity type formed in a portion of the of the epitaxial layer, wherein the doping region partially comprises doped polysilicon materials having the second conductivity type; a gate dielectric layer formed over the epitaxial layer, partially overlying the well region; and a gate electrode formed over a portion of the gate dielectric layer.