Abstract: By providing a novel bipolar device design implementation, a standard CMOS process (105-109) can be used unchanged to fabricate useful bipolar transistors (80) and other bipolar devices having adjustable properties by partially blocking the P or N well doping (25) used for the transistor base (581). This provides a hump-shaped base (583, 584) region with an adjustable base width (79), thereby achieving, for example, higher gain than can be obtained with the unmodified CMOS process (101-104) alone. By further partially blocking the source/drain doping step (107) used to form the emitter (74) of the bipolar transistor (80), the emitter shape and effective base width (79) can be further varied to provide additional control over the bipolar device (80) properties. The embodiments thus include prescribed modifications to the masks (57, 62, 72, 46) associated with the bipolar device (80) that are configured to obtain desired device properties.

Abstract: A semiconductor device includes a semiconductor substrate, a gate pattern disposed on the semiconductor substrate, a body region disposed on the gate pattern and a first impurity doping region and a second impurity doping region. The gate pattern is disposed below the body region and the first impurity doping region and the second impurity doping region.

Abstract: Embodiments relate to a bipolar transistor that includes a body region having a fin structure. At least one terminal region may be formed over at least a portion of the body region. The at least one terminal region may be formed as an epitaxially grown region. Embodiments also relate to a vertically integrated electronic device that includes a first terminal region, a second terminal region and a third terminal region. The second terminal region may be arranged over at least a portion of the third terminal region, and at least two of the first, second and third terminal regions may be formed as epitaxially grown regions.

Abstract: An electrostatic discharge protection circuit has a bipolar transistor which includes a first diffusion layer of a first conductive type connected with a first power supply and functioning as a base; a second diffusion layer of a second conductive type connected with a second power supply and functioning as a collector; and a third diffusion layer of the second conductive type connected with an input/output pad and functioning as an emitter. An area of a first region of the third diffusion layer which is opposite to the first diffusion layer is larger than an area of a second region of the second diffusion layer which is opposite to the first diffusion layer.

Abstract: A semiconductor device is presented, which includes a semiconductor substrate with a high concentration impurity of a first type conductivity and an epitaxial layer with a low concentration impurity provided on the semiconductor substrate, where a trench coupled to the semiconductor substrate is provided in the epitaxial layer with the low concentration impurity. And the semiconductor device further includes a high concentration impurity region of the first type conductivity having the same type conductivity as the type of the semiconductor substrate formed in at least the epitaxial layer with the low concentration impurity along an inner wall of the trench and coupled to the semiconductor substrate with the high concentration impurity of a first type conductivity, and contacts formed on the high concentration impurity region of the first type conductivity.

Abstract: In order to reduce a device area, a bipolar transistor using temperature characteristics of a forward voltage generated between an emitter and a base has a structure in which a high concentration second conductivity type impurity region for a base electrode and a high concentration first conductivity type impurity region for a collector electrode are brought into direct contact with each other to prevent formation of an unnecessary isolation region. Further, an emitter region is disposed to self-align with a device isolation insulating film or a polycrystalline silicon arranged on a surface of a semiconductor substrate.

Abstract: Device structure for active devices fabricated in a semiconductor-on-insulator (SOI) substrate and design structures for a radiofrequency integrated circuit. The device structure includes a first isolation region in the semiconductor layer that extends from a top surface of a semiconductor layer to a first depth, a second isolation region in the semiconductor layer that extends from the top surface of the semiconductor layer to a second depth greater than the first depth, and a first doped region in the semiconductor layer. The first doped region is disposed vertically between the first isolation region and an insulating layer disposed between the semiconductor layer and a handle wafer of the SOI substrate. The device structure may be included in a design structure embodied in a machine readable medium for designing, manufacturing, or testing an integrated circuit.

Abstract: A bipolar high voltage/power semiconductor device has a drift region having adjacent its ends regions of different conductivity types respectively. High and low voltage terminals are provided. A first insulated gate terminal and a second insulated gate terminal are also provided. One or more drive circuits provide appropriate voltages to the first and second insulated gate terminals so as to allow current conduction in a first direction or in a second direction that is opposite the first direction.

Abstract: The present invention provides a method of forming a bipolar transistor. The method includes doping a silicon layer with a first type of dopant and performing a first implant process to implant dopant of a second type opposite the first type in the silicon layer. The implanted dopant has a first dopant profile in the silicon layer. The method also includes performing a second implant process to implant additional dopant of the second type in the silicon layer. The additional implanted dopant has a second dopant profile in the silicon layer different than the first dopant profile. The method further includes growing an insulating layer formed over the silicon layer by consuming a portion of the silicon layer and the first type of dopant.

Abstract: A bipolar transistor is formed on a heavily doped silicon substrate (1). An epitaxially grown collector (12) is formed on the substrate (1) and comprises silicon containing germanium at least at the top of the collector (12). An epitaxial base (13) is formed on the collector (12) to have the opposite polarity and also comprises silicon containing germanium at least at the bottom of the base (13). An emitter is formed at the top of the base (13) and comprises polysilicon doped to have the same polarity as the collector (12).

Abstract: The present invention provides a technology that makes it possible to enhance the gain and the efficiency of an RF bipolar transistor. Device isolation is given between a p+ type isolation region and an n+ type collector embedded region and between a p+ type isolation region and an n type collector region (an n+ type collector extraction region) with an isolation section that surrounds the collector extraction region in a plan view and is formed by embedding a dielectric film in a groove penetrating an isolation section, a collector region, and a collector embedded region and reaching a substrate. Further, a current route is formed between an emitter wiring (a wiring) and the substrate with an electrically conductive layer formed by embedding the electrically conductive layer in a groove penetrating a dielectric film, silicon oxide films, a semiconductor region, and the isolation regions and reaching the substrate, and thereby the impedance between the emitter wiring and the substrate is reduced.

Abstract: The invention provides a bipolar transistor with an improved performance because of a reduced collector series resistance and a reduced collector to substrate capacitance. The bipolar transistor includes a protrusion (5) which size may be reduced to a dimension that cannot be achieved with lithographic techniques. The protrusion (5) comprises a collector region (21) and a base region (22), in which the collector region (21) covers and electrically connects to a first portion of a first collector connecting region (3). A second collector connecting region (13) covers a second portion of the first collector connecting region (3) and is separated from the protrusion (5) by an insulation layer (10, 11), which covers the sidewalls of the protrusion (5). A contact to the base region (22) is provided by a base connecting region (15), which adjoins the protrusion (5) and which is separated from the second collector connecting region (13) by an insulation layer (14).

Abstract: Stress-modified device structures, methods of fabricating such stress-modified device structures, and design structures for an integrated circuit. An electrical characteristic of semiconductor devices formed on a common substrate, such as the current gains of bipolar junction transistors, may be altered by modifying stresses in structures indirectly on or over, or otherwise indirectly coupled with, the semiconductor devices. The structures, which may be liners for contacts in a contact level of an interconnect, are physically spaced away from, and not in direct physical contact with, the respective semiconductor devices because at least one additional intervening material or structure is situated between the stress-imparting structures and the stress-modified devices.

Abstract: The invention relates to a semiconductor device with a substrate (11) and a semiconductor body (11) comprising a bipolar transistor with an emitter region (1), a base region (2) and a collector region (3) comprising a first, a second and a third connection conductor, which emitter region (1) comprises a mesa-shaped emitter connection region (1A) provided with spacers (4) and adjacent thereto a base connection region (2A) comprising a conductive region (2AA) of poly crystalline silicon. In a device (10) according to the invention, the base connection region (2A) comprises a further conducting region (2AB), which is positioned between the conductive region (2AA) of poly crystalline silicon and the base region (2) and which is made of a material with respect to which the conducting region (2AA) of polycrystalline silicon is selectively etchable. Such a device (10) is easy to manufacture by means of a method according to the invention and its bipolar transistor possesses excellent RF properties.

Abstract: The invention relates to a semiconductor device (10) with a semiconductor body (12) comprising a bipolar transistor with an emitter region, a base region and a collector region (1, 2, 3) of, respectively, a first conductivity type, a second conductivity type opposite to the first conductivity type, and the first conductivity type. One of the emitter or collector regions (1, 3) comprises a nanowire (30). The base region (2) has been formed from a layer (20) at the surface of the semiconductor body (12); the other one (3, 1) of the emitter or collector regions (1, 3) has been formed in the semiconductor body (12) below the base region (2). The emitter or collector region (1, 3) comprising the nanowire (30) has been provided on the surface of the semiconductor body (12) such that its longitudinal axis extends perpendicularly to the surface.

Abstract: The invention relates to a semiconductor device (10) with a substrate (12) and a semiconductor body (11) of silicon comprising a bipolar transistor with an emitter region, a base region and a collector region (1,2,3) first conductivity type, a second conductivity type opposite to said first conductivity type and the first conductivity type, respectively, with a first semiconductor region (3) comprising the collector region or the emitter region being formed in the semiconductor body (11), on top of which a second semiconductor region (2) comprising the base region is present, on top of which a third semiconductor region (1) comprising the other of said collector region and said emitter region is present, said semiconductor body (11) being provided with a constriction at the location of the transition between the first and the second semiconductor region (3, 2), which constriction has been formed by means of an electrically insulating region (26, 27) buried in the semiconductor body (11).

Abstract: Methods are disclosed for forming a varied impurity profile for a collector using scattered ions while simultaneously forming a subcollector. In one embodiment, the invention includes: providing a substrate; forming a mask layer on the substrate including a first opening having a first dimension; and substantially simultaneously forming through the first opening a first impurity region at a first depth in the substrate (subcollector) and a second impurity region at a second depth different than the first depth in the substrate. The breakdown voltage of a device can be controlled by the size of the first dimension, i.e., the distance of first opening to an active region of the device. Numerous different sized openings can be used to provide devices with different breakdown voltages using a single mask and single implant. A semiconductor device is also disclosed.

Abstract: An ESD protection device comprises a substrate of a first conductive type; a transistor formed in the substrate having an input terminal of the first conductive type, a control terminal of a second conductive type, and a ground terminal of the first conductive type; and a diode formed in the substrate having a first terminal of the first conductive type and a second terminal of the second conductive type, wherein the input terminal and the second terminal are coupled to an input, and the ground terminal and the first terminal are coupled to a ground.

Abstract: The present invention provides a technology that makes it possible to enhance the gain and the efficiency of an RF bipolar transistor. Device isolation is given between a p+ type isolation region and an n+ type collector embedded region and between a p+ type isolation region and an n type collector region (an n+ type collector extraction region) with an isolation section that surrounds the collector extraction region in a plan view and is formed by embedding a dielectric film in a groove penetrating an isolation section, a collector region, and a collector embedded region and reaching a substrate. Further, a current route is formed between an emitter wiring (a wiring) and the substrate with an electrically conductive layer formed by embedding the electrically conductive layer in a groove penetrating a dielectric film, silicon oxide films, a semiconductor region, and the isolation regions and reaching the substrate, and thereby the impedance between the emitter wiring and the substrate is reduced.

Abstract: A semiconductor device is described. The semiconductor device comprises a protected device in a protected device area of a substrate. An electrostatic discharge power clamp device comprising an outer first guard ring and an inner second guard ring is in a guard ring area of the substrate, enclosing the protected device. The first guard ring comprises a first well region having a first conductive type. A first doped region having the first conductive type and a second doped region having a second conductive type are in the first well region. The second guard ring comprises a second well region having a second conductive type. A third doped region has the second conductive type in the second well region. An input/output device is in a periphery device area, coupled to the electrostatic discharge power clamp device.

Abstract: Provided is a power semiconductor device including a guard ring region to protect control devices. The power semiconductor device includes a semiconductor body layer extending over a semiconductor substrate of a first conductivity type. The semiconductor body layer has a second conductivity type opposite the first conductivity type. A well of the first conductivity type extends in the semiconductor body layer and is configured to be electrically insulated from the semiconductor substrate. At least one control device is formed in the well, where the control device comprises at least one of PN junction. A guard ring region of the first conductivity type is laterally spaced from but surrounds the well. The guard ring region together with the semiconductor substrate and the semiconductor body layer form a parasitic bipolar transistor, and the guard ring region functions as a collector of the parasitic bipolar transistor.

Abstract: The collector resistance of a bipolar junction transistor that is formed in a CMOS process is substantially reduced by forming a heavily-doped collector extension region that extends from a heavily-doped collector contact region down to a deep well of the same conductivity type to a point that lies close to the base of the transistor.

Abstract: A bipolar power transistor does not include integration of a Zener diode electrically connected between the base and collector for limiting the collector voltage. The power transistor is formed in a substrate, and includes an equalization diffusion and an auxiliary diffusion forming a P-N junction along a perimeter of the substrate. An equalization conduction layer is in contact with the equalization diffusion and the auxiliary diffusion for electrically shorting the P-N junction.

Abstract: Bipolar transistors in complimentary MOS (CMOS) integrated circuits (ICs) are often fabricated as parasitic components, in which emitters of bipolar transistors are implanted in the same processes as CMOS sources/drains, to avoid manufacturing costs associated with dedicated implants for bipolar emitters. Energies and doses of CMOS source/drain implants are typically selected to optimize CMOS transistor performance, resulting in less than optimum values of bipolar parameters such as gain. CMOS ICs often include implanted resistors of a same type as the emitters of the bipolar transistors in the same ICs. This invention discloses bipolar transistors with emitters implanted by CMOS source/drain implants and resistor implants to improve bipolar transistor parameters, and a method for fabricating same.

Abstract: The present invention provides a semiconductor device that includes a plurality of transistor cells and makes it possible to achieve higher degree of integration and lower cost of an integrated semiconductor circuit device as the first object, and provide an integrated semiconductor circuit device of high density integration and compact construction at a low cost.

Abstract: An electrostatic discharge protection device comprising a multi-finger gate, a first lightly doped region of a second conductivity, a first heavily doped region of the second conductivity, and a second lightly doped region of the second conductivity. The multi-finger gate comprises a plurality of fingers mutually connected in parallel over an active region of a first conductivity. The first lightly doped region of a second conductivity is disposed in the semiconductor substrate and between two of the fingers. The first heavily doped region of the second conductivity is disposed in the first lightly doped region of the second conductivity. The second lightly doped region of the second conductivity is beneath and adjoins the first lightly doped region of the second conductivity.

Abstract: A method of fabricating an heterojunction bipolar transistor (HBT) structure in a bipolar complementary metal-oxide-semiconductor (BiCMOS) process selectively thickens an oxide layer overlying a base region in areas that are not covered by a temporary emitter and spacers such that the temporary emitter can be removed and the base-emitter junction can be exposed without also completely removing the oxide overlying the areas of the base region that are not covered by the temporary emitter or spacers. As a result, a photomask is not required to remove the temporary emitter and to expose the base-emitter junction.

Abstract: An electro-static discharge protection device includes a first conductive type well and a second conductive type well which are formed in a surface of the first conductive type layer or a first conductive type substrate. A first high concentration second conductive type region, a first high concentration first conductive type region, and a second high concentration second conductive type region are formed in a surface of the second conductive type well. A third high concentration second conductive type region is formed in a surface of the first conductive type well. The first high concentration second conductive type region and the first high concentration first conductive type region are connected with a first power supply of a potential. The third high concentration second conductive type region is connected with a second power supply having a potential different from the potential of the first power supply.

Abstract: A protective SCR integrated circuit device is disclosed built on adjacent N and P wells and defining an anode and a cathode. In addition to the anode and cathode contact structures, the device has an n-type stack (N+/ESD) structure bridging the N-Well and the P-Well, and a p-type stack (P+/PLDD) structure in the P-Well. The separation of the n-type stack structure and the p-type stack structure provides a low triggering voltage, that together with other physical dimensions and processing parameters also provide a relatively high holding voltage. In an embodiment, the triggering voltage may be about 8V while exhibiting a holding voltage, that may be controlled by the lateral dimension of the n-type stack of about 5-7 V.

Abstract: A method realizes a contact of a first well of a first type of dopant integrated in a semiconductor substrate next to a second well of a second type of dopant and forming with it a parasitic diode. The method comprises: formation of the first well; formation of the second well next to the first well; definition of an oxide layer above the first and second wells; and formation of an electric contact layer above the oxide layer in correspondence with the first well for realizing an electric contact with it. The definition step of the oxide layer further comprises a deposition step of this oxide layer above the whole first well and a removal step of at least one portion of the oxide layer in correspondence with a contact area of the first well so that the contact area has a shorter length than a length of the first well.

Abstract: An electric discharge device includes a bipolar transistor configuration comprising a base, an emitter, and a collector. At least one pinched resistor is formed in a region comprising both the base and emitter so as to produce a pinched resistive area that develops a voltage once the bipolar transistor experiences junction breakdown.

Abstract: A bipolar transistor is formed in an isolation structure comprising a floor isolation region, a dielectric filled trench above the floor isolation region and a sidewall isolation region extending downward from the bottom of the trench to the floor isolation region. This structure provides a relatively deep isolated pocket in a semiconductor substrate while limiting the depth of the trench that must be etched in the substrate.

Abstract: A bipolar transistor and a method for manufacturing the same. The bipolar transistor can include a collector region formed in a substrate, an epitaxial layer formed over the substrate including the collector region, a base region formed in the epitaxial layer, an emitter region formed in the base region, an oxide layer formed on sidewalls of a trench extending through the emitter region, the base region, the epitaxial layer and in the collector region, and a polysilicon layer formed in the trench.

Abstract: A bipolar transistor structure and related methods for fabrication thereof are provided. A vertical spacer layer is selectively deposited after implanting an extrinsic base region into a semiconductor substrate while using an ion implantation mask located upon a screen dielectric layer located upon the semiconductor substrate. A portion of the ion implantation mask may remain embedded and aligned within a sidewall of an aperture within the vertical spacer layer. The selective deposition of the vertical spacer layer allows for a reduced thermal budget and reduced process complexity when fabricating the bipolar transistor.

Abstract: High performance bipolar transistors with raised extrinsic self-aligned base are integrated into a BiCMOS structure containing CMOS devices. By forming pad layers and raising the height of an intrinsic base layer relative to the source and drain of preexisting CMOS devices and by forming an extrinsic base through selective epitaxy, the effect of topographical variations is minimized during a lithographic patterning of the extrinsic base. Also, by not employing any chemical mechanical planarization process during the fabrication of the bipolar structures, complexity of process integration is reduced. Internal spacers or external spacers may be formed to isolate the base from the emitter. The pad layers, the intrinsic base layer, and the extrinsic base layer form a mesa structure with coincident outer sidewall surfaces.

Abstract: In a semiconductor device according to the present invention, two epitaxial layers are formed on a P type substrate. In the substrate and the epitaxial layers, isolation regions are formed to divide the substrate and the epitaxial layers into a plurality of islands. Each of the isolation regions is formed by connecting first and second P type buried layers with a P type diffusion layer. By disposing the second P type buried layer between the first P type buried layer and the P type diffusion layer, a lateral diffusion width of the first P type buried layer is reduced. By use of this structure, a formation region of the isolation region is reduced in size.

Abstract: Embodiments of the invention provide a semiconductor device including a collector in an active region; a first and a second sub-collector, the first sub-collector being a heavily doped semiconductor material adjacent to the collector and the second sub-collector being a silicided sub-collector next to the first sub-collector; and a silicided reach-through in contact with the second sub-collector, wherein the first and second sub-collectors and the silicided reach-through provide a continuous conductive pathway for electrical charges collected by the collector from the active region. Embodiments of the invention also provide methods of fabricating the same.

Abstract: Methods of boosting the performance of bipolar transistor, especially SiGe heterojunction bipolar transistors, is provided together with the structure that is formed by the inventive methods. The methods include providing a species-rich dopant region comprising C, a noble gas, or mixtures thereof into at least a collector. The species-rich dopant region forms a perimeter or donut-shaped dopant region around a center portion of the collector. A first conductivity type dopant is then implanted into the center portion of the collector to form a first conductivity type dopant region that is laterally constrained, i.e., confined, by the outer species-rich dopant region.

Abstract: An insulated gate bipolar transistor (IGBT) includes a substrate having a first conductivity type, a drift layer having a second conductivity type opposite the first conductivity type, and a well region in the drift layer and having the first conductivity type. An epitaxial channel adjustment layer is on the drift layer and has the second conductivity type. An emitter region extends from a surface of the epitaxial channel adjustment layer through the epitaxial channel adjustment layer and into the well region. The emitter region has the second conductivity type and at least partially defines a channel region in the well region adjacent to the emitter region. A gate oxide layer is on the channel region, and a gate is on the gate oxide layer. Related methods are also disclosed.

Abstract: The present invention provides a semiconductor technology capable of suppressing an increase in threshold voltage of a transistor and, also, improving a withstand voltage between a source region and a drain region. Source and drain regions of a p channel type MOS transistor are formed in an n? type semiconductor layer in an SOI substrate. In addition, an n type impurity region is formed in the semiconductor layer. The impurity region is formed over the entire bottom of the source region at a portion directly below this source region, and is also formed directly below the semiconductor layer between the source region and the drain region. A peak position of an impurity concentration in the impurity region is set below a lowest end of the source region at a portion directly below an upper surface of the semiconductor layer between the source region and the drain region.

Abstract: A method of forming bipolar transistors by using the same mask to form the collector region in a substrate of an opposite conductivity type as to form the base in the collector region. More specifically, impurities of a first conductivity type are introduced into a region of a substrate of a second conductivity type through a first aperture in a first mask to form a collector region. Impurities of the second conductivity type are introduced in the collector through the first aperture in the first mask to form the base region. Impurities of the first conductivity type are then introduced into the base region through a second aperture in a second mask to form the emitter region. The minimum dimension of the first aperture of the first mask is selected for a desired collector to base breakdown voltage. This allows tuning of the breakdown voltage.

Abstract: The present invention provides a method for depositing a dielectric stack comprising forming a dielectric layer atop a substrate, the dielectric layer comprising at least oxygen and silicon atoms; forming a layer of metal atoms atop the dielectric layer within a non-oxidizing atmosphere, wherein the layer of metal atoms has a thickness of less than about 15 ?; forming an oxygen diffusion barrier atop the layer of metal atoms, wherein the non-oxidizing atmosphere is maintained; forming a gate conductor atop the oxygen diffusion barrier; and annealing the layer of metal atoms and the dielectric layer, wherein the layer of metal atoms reacts with the dielectric layer to provide a continuous metal oxide layer having a dielectric constant ranging from about 25 to about 30 and a thickness less than about 15 ?.

Abstract: Disclosed is a bipolar complementary metal oxide semiconductor (BiCMOS) or NPN/PNP device that has a collector, an intrinsic base above the collector, shallow trench isolation regions adjacent the collector, a raised extrinsic base above the intrinsic base, a T-shaped emitter above the extrinsic base, spacers adjacent the emitter, and a silicide layer that is separated from the emitter by the spacers.

Abstract: Disclosed are apparatus and methods for designing electrical contact for a bipolar emitter structure. The area of an emitter structure (106, 306, 400, 404) and the required current density throughput of an electrical contact structure (108, 308, 402, 406) are determined. A required electrical contact area is determined based on the required current density, and the electrical contact structure is then designed to minimize the required electrical contact area with respect to the emitter structure area.

Abstract: A method of forming a semiconductor device having two different strains therein is provided. The method includes forming a strain in a first region with a first straining film, and forming a second strain in a second region with a second straining film. Either of the first or second strains may be either tensile or compressive. Additionally the strains may be formed at right angles to one another and may be additionally formed in the same region. In particular a vertical tensile strain may be formed in a base and collector region of an NPN bipolar transistor and a horizontal compressive strain may be formed in the extrinsic base region of the NPN bipolar transistor. A PNP bipolar transistor may be formed with a compression strain in the base and collector region in the vertical direction and a tensile strain in the extrinsic base region in the horizontal direction.

Abstract: A bulk-doped semiconductor that is at least one of the following: a single crystal, an elongated and bulk-doped semiconductor that, at any point along its longitudinal axis, has a largest cross-sectional dimension less than 500 nanometers, and a free-standing and bulk-doped semiconductor with at least one portion having a smallest width of less than 500 nanometers. Such a semiconductor may comprise an interior core comprising a first semiconductor; and an exterior shell comprising a different material than the first semiconductor. Such a semiconductor may be elongated and may have, at any point along a longitudinal section of such a semiconductor, a ratio of the length of the section to a longest width is greater than 4:1, or greater than 10:1, or greater than 100:1, or even greater than 1000:1.

Abstract: A method for fabricating a bipolar junction transistor on a wafer is disclosed. The wafer has a N-type doped area and a plurality of isolated structures. A protection layer is formed on the wafer and portions of the protection layer are then removed to expose portions of the doped area. A P-type epitaxy layer is formed on the protection layer and the first doped area and then portions of the epitaxy layer and the protection layer are removed. An insulation layer is formed and at least a collector opening and emitter opening are formed within the insulation layer. Following that, a polysilicon layer is formed to fill the collector opening and the emitter opening. A spacer is formed beside the polysilicon layer and the epitaxy layer followed by performing a self-aligned silicidation process to form a salicide layer on the polysilicon layer and portions of the epitaxy layer.