Abstract: A semiconductor structure includes a substrate; an isolation structure in the substrate, wherein the isolation structure defines a region therein; a first semiconductor region having at least a portion in the region defined by the isolation structure, wherein the first semiconductor region is of a first conductivity type; a second semiconductor region on the first semiconductor region, wherein the second semiconductor region is of a second conductivity type opposite the first conductivity type; and a third semiconductor region of the first conductivity type on the second semiconductor region, wherein the third semiconductor region has at least a portion higher than a top surface of the isolation structure.

Abstract: A Semiconductor component that contains AlxGayIn1-x-yAszSb1-z, whereby the parameters x, y, and z are selected such that a bandgap of less than 350 meV is achieved, whereby it features a mesa-structuring and a passivation layer containing AlnGa1-nAsmSb1-m is applied at least partially on at least one lateral surface of the structuring, and the parameter n is selected in the range of 0.4 to 1 and the parameter m in the range of 0 to 1.

Abstract: An n+-emitter layer arranged under an emitter electrode is formed of convex portions arranged at predetermined intervals and a main body coupled to the convex portions. A convex portion region is in contact with the emitter electrode, and a p+-layer doped more heavily than a p-base layer is arranged at least below the emitter layer. In a power transistor of a lateral structure, a latch-up immunity of a parasitic thyristor can be improved, and a turn-off time can be reduced.

Abstract: The mobility of charge carriers in a bipolar (BJT) device is increased by creating compressive strain in the device to increase mobility of electrons in the device, and creating tensile strain in the device to increase mobility of holes in the device. The compressive and tensile strain are created by applying a stress film adjacent an emitter structure of the device and atop a base film of the device. In this manner, the compressive and tensile strain are located in close proximity to an intrinsic portion of the device. A suitable material for the stress film is nitride. The emitter structure may be “T-shaped”, having a lateral portion atop an upright portion, a bottom of the upright portion forms a contact to the base film, and the lateral portion overhangs the base film.

Abstract: Semiconductor device structures for use with bipolar junction transistors and methods of fabricating such semiconductor device structures. The semiconductor device structure includes a semiconductor body having a top surface and sidewalls extending from the top surface to an insulating layer, a first region including a first semiconductor material with a first conductivity type, and a second region including a second semiconductor material with a second conductivity type. The first and second regions each extend across the top surface and the sidewalls of the semiconductor body. The device structure further includes a junction defined between the first and second regions and extending across the top surface and the sidewalls of the semiconductor body.

Abstract: A bipolar transistor structure comprises a semiconductor substrate having a first conductivity type, a collector region having a second conductivity type that is opposite the first conductivity type formed in a substrate active device region defined by isolation dielectric material formed in an upper surface of the semiconductor substrate, a base region that includes an intrinsic base region having the first conductivity type formed over the collector region and an extrinsic base region having the second conductivity type formed over the isolation dielectric material, and a sloped in-situ doped emitter plug having the second conductivity type formed on the intrinsic base region.

Abstract: A high-frequency bipolar transistor includes an emitter contact adjoining an emitter connection region, a base contact adjoining a base connection region, and a collector contact adjoining a collector connection region. A first insulation layer is disposed on the base connection region. The collector connection region contains a buried layer, which connects the collector contact to a collector zone. A silicide or salicide region is provided on the buried layer and connects the collector contact to the collector zone in a low-impedance manner. A second insulation layer is disposed on the collector connection region but not on the silicide region.

Abstract: An IGBT is disclosed which has a set of inside trenches and an outside trench formed in its semiconductor substrate. The substrate has emitter regions adjacent the trenches, a p-type base region adjacent the emitter regions and trenches, and an n-type base region comprising a first and a second subregion contiguous to each other. The first subregion of the n-type base region is contiguous to the inside trenches whereas the second subregion, less in impurity concentration than the first, is disposed adjacent the outside trench. Breakdown is easier to occur than heretofore adjacent the inside trenches, saving the device from destruction through mitigation of a concentrated current flow adjacent the outside trench.

Abstract: A heterojunction bipolar transistor (HBT) is provided with an improved on-state breakdown voltage VCE. The improvement of the on-state breakdown voltage for the HBT improves the output power characteristics of the HBT and the ability of the HBT to withstand large impedance mismatch (large VSWR). The improvement in the on-state breakdown voltage is related to the suppression of high electric fields adjacent a junction of a collector layer and a sub-collector layer forming a collector region of the HBT.

Abstract: High voltage bipolar transistors built with a BiCMOS process sequence exhibit reduced gain at high current densities due to the Kirk effect. Threshold current density for the onset of the Kirk effect is reduced by the lower doping density required for high voltage operation. The widened base region at high collector current densities due to the Kirk effect extends laterally into a region with a high density of recombination sites, resulting in an increase in base current and drop in the gain. The instant invention provides a bipolar transistor in an IC with an extended unsilicided base extrinsic region in a configuration that does not significantly increase a base-emitter capacitance. Lateral extension of the base extrinsic region may be accomplished using a silicide block layer, or an extended region of the emitter-base dielectric layer. A method of fabricating an IC with the inventive bipolar transistor is also disclosed.

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: Methods for forming a SiC BJT having a low base resistance and minimal emitter width are provided. The methods incorporate a plated shadow metal layer overhanging the emitter mesa. The mushroom-shaped shadow metal layer can then act as either a deposition shadow mask or an ion implantation mask in subsequent steps for forming base contacts. In this way, base contacts can be formed with a variable and controllable distance from the emitter mesa defined by the lateral extent of overhang of the shadow metal layer. The same shadow masking effect can also be used to form self-aligned emitter and base wiring metals for reduction of resistance. Plating of the emitter contact layer allows avoiding subsequent photolithography steps on the top of emitter mesa; thus emitter mesa width could be minimized.

Abstract: A vertical heterobipolar transistor comprising a substrate of semiconductor material of a first conductivity type and an insulation region provided therein, a first semiconductor electrode arranged in an opening of the insulation region and comprising monocrystalline semiconductor material of a second conductivity type, which is either in the form of a collector or an emitter, and which has a first heightwise portion and an adjoining second heightwise portion which is further away from the substrate interior in a heightwise direction, wherein only the first heightwise portion is enclosed by the insulation region in lateral directions perpendicular to the heightwise direction, a second semiconductor electrode of semiconductor material of the second conductivity type, which is in the form of the other type of semiconductor electrode, a base of monocrystalline semiconductor material of the first conductivity type, and a base connection region having a monocrystalline portion which in a lateral direction laterall

Abstract: A bipolar junction transistor includes a collector having a first conductivity type, a drift layer having the first conductivity type on the collector, a base layer on the drift layer and having a second conductivity type opposite the first conductivity type, a lightly doped buffer layer having the first conductivity type on the base layer and forming a p-n junction with the base layer, and an emitter mesa having the first conductivity type on the buffer layer and having a sidewall. The buffer layer includes a mesa step adjacent to and spaced laterally apart from the sidewall of the emitter mesa, and a first thickness of the buffer layer beneath the emitter mesa is greater than a second thickness of the buffer layer outside the mesa step.

Abstract: A bipolar transistor is provided which includes a collector region, an intrinsic base region overlying the collector region and an emitter region overlying the intrinsic base region. An extrinsic base overlies a portion of the intrinsic base region. An epitaxial spacer layer is disposed between the collector region and the intrinsic base region in locations not underlying the emitter region.

Abstract: Semiconductor device structures for use with bipolar junction transistors and methods of fabricating such semiconductor device structures. The semiconductor device structure comprises a semiconductor body having a top surface and sidewalls extending from the top surface to an insulating layer, a first region including a first semiconductor material with a first conductivity type, and a second region including a second semiconductor material with a second conductivity type. The first and second regions each extend across the top surface and the sidewalls of the semiconductor body. The device structure further comprises a junction defined between the first and second regions and extending across the top surface and the sidewalls of the semiconductor body.

Abstract: The invention relates to a semiconductor device (10) with a substrate (11) and a semiconductor body (12) comprising a vertical 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, wherein the collector region (3) comprises a first sub-region (3A) bordering the base region (2) and a second sub-region (3B) bordering the first sub-region (3A) which has a lower doping concentration than the second sub-region (3B), and the transistor is provided with a gate electrode (5) which laterally borders the first sub-region (3A) and by means of which the first sub-region (3A) may be depleted.

Abstract: There is provided a bipolar transistor (with a respective fabrication method) that provides superior noise characteristics and gain diffusion. The fabricating method includes forming a first base region at a collector region, which in turn is formed on a substrate. A first silicon layer is formed on the base region, and a second silicon layer is formed on the first silicon layer using a forming method different from the method used in forming the first silicon layer. An emitter region is then formed from impurities at the base region by performing a thermal process.

Abstract: According to one exemplary embodiment, a bipolar transistor includes an active area situated between first and second isolation regions in a substrate. The bipolar transistor further includes an epitaxial extension layer situated on the active area, where the epitaxial extension layer extends over the first and second isolation regions. The bipolar transistor further includes a base layer situated on the epitaxial extension layer, where the base layer includes an epitaxial base, and where the epitaxial base includes a usable emitter formation area. The active area has a first width and the usable emitter formation area has a second width, where the second width is at least as large as the first width.

Abstract: A semiconductor device including a bipolar transistor in which the collector resistance. The bipolar transistor includes a first conduction type semiconductor substrate having a main surface. A second conduction type collector region is formed in the semiconductor substrate. A shallow trench isolation structure isolates the main surface of the semiconductor substrate into two insulated active regions. A collector leading portion is formed in one of the active regions. A first conduction type base region and a second conduction type emitter region are formed on the other one of the active regions. The collector region has a first depth from the main surface immediately below the shallow trench isolation structure, and the collector region has a second depth from the main surface immediately below the two active regions. The first depth is less than the second depth.

Abstract: An integrated circuit including a buried layer of determined conductivity type in a plane substantially parallel to the plane of a main circuit surface, in which the median portion of this buried layer is filled with a metal-type material.

Abstract: Methods, devices, and systems for using and forming vertically base-connected bipolar transistors have been shown. The vertically base-connected bipolar transistors in the embodiments of the present disclosure are formed with a CMOS fabrication technique that decreases the transistor size while maintaining the high performance characteristics of a bipolar transistor.

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: A substrate has a collector region of a first conductivity type, and a base layer of a single crystalline structure and including impurities of a second conductivity type is located over the collector region. An emitter region is defined at least in part by impurities of the first conductivity type contained in the base layer. An emitter electrode of the first conductivity type contacts the emitter region, and at least a portion of the emitter electrode which is in contact with the emitter region has a single crystalline structure.

Abstract: A bipolar-junction transistor is disclosed comprising a first layer, a second layer, and a third layer, the surfaces of the layers modified for more precise control of electron function. The surfaces are modified to have a periodically repeating structure of indents where the indentations are of dimensions so as to create de Broglie wave interference, leading to a change in electron work function.

Abstract: The present invention relates to a semiconductor device comprising first and second active device regions that are located in a semiconductor substrate and are isolated from each other by an isolation region therebetween, while the semiconductor device comprises a first conductive interconnect structure that is embedded in the isolation region and connects the first active device region with the second active device region. The semiconductor device preferably contains at least one static random access memory (SRAM) cell located in the semiconductor substrate, and the first conductive interconnect structure cross-connects a pull-down transistor of the SRAM cell with a pull-up transistor thereof. The conductive interconnect preferably comprises doped polysilicon and can be formed by processing steps including photolithographic patterning, etching, and polysilicon deposition.

Abstract: The mobility of charge carriers in a bipolar (BJT) device is increased by creating compressive strain in the device to increase mobility of electrons in the device, and creating tensile strain in the device to increase mobility of holes in the device. The compressive and tensile strain are created by applying a stress film adjacent an emitter structure of the device and atop a base film of the device. In this manner, the compressive and tensile strain are located in close proximity to an intrinsic portion of the device. A suitable material for the stress film is nitride. The emitter structure may be “T-shaped”, having a lateral portion atop an upright portion, a bottom of the upright portion forms a contact to the base film, and the lateral portion overhangs the base film.

Abstract: An n+-emitter layer arranged under an emitter electrode is formed of convex portions arranged at predetermined intervals and a main body coupled to the convex portions. A convex portion region is in contact with the emitter electrode, and a p+-layer doped more heavily than a p-base layer is arranged at least below the emitter layer. In a power transistor of a lateral structure, a latch-up immunity of a parasitic thyristor can be improved, and a turn-off time can be reduced.

Abstract: A metal-oxide-semiconductor (MOS) transistor device is provided. The MOS transistor device includes a substrate, a gate structure, a spacer, a source/drain region and a barrier layer. The gate structure is disposed on the substrate. The gate structure includes a gate and a gate dielectric layer disposed between the gate and the substrate. The spacer is disposed on the sidewall of the gate structure. The source/drain region is disposed in the substrate on two sides of the spacer. The barrier layer is disposed around the source/drain region. The source/drain region and the barrier layer are fabricated using an identical material. However, the doping concentration of the source/drain region is larger than the doping concentration of the barrier layer.

Abstract: In conventional mesa-type npn bipolar transistors, the improvement of a current gain and the miniaturization of the transistor have been unachievable simultaneously as a result of a trade-off being present between lateral diffusion and recombination of the electrons which have been injected from an emitter layer into a base layer, and a high-density base contact region—emitter mesa distance. In contrast to the above, the present invention is provided as follows: The gradient of acceptor density in the depth direction of a base layer is greater at the edge of an emitter layer than at the edge of a collector layer. Also, the distance between a first mesa structure including the emitter layer and the base layer, and a second mesa structure including the base layer and the collector layer, is controlled to range from 3 ?m to 9 ?m.

Abstract: By a non-selective epitaxial growth method, an SiGe film is grown on the whole surface of a silicon oxide film so as to cover an inner wall of a base opening. Here, such film forming conditions are selected that, inside the base opening, a bottom portion is formed of single crystal, other portions such as a sidewall portion are formed of polycrystalline, and a film thickness of the sidewall portion is less than or equal to 1.5 times the film thickness of the bottom portion. In this non-selective epitaxial growth, monosilane, hydrogen, diborane, and germane are used as source gases. Then, flow rates of monosilane and hydrogen are set to 20 sccm and 20 slm respectively. Also, a growth temperature is set to 650° C., a flow rate of diborane is set to 75 sccm, and a flow rate of germane is set to 35 sccm.

Abstract: A bipolar transistor having enhanced characteristics is fabricated by etching a base mesa, which is formed below an emitter mesa (upper emitter layer) and a base electrode, so as to have jut regions on the edges of its generally rectangular region. A mask film, e.g., insulating film, is formed to cover the rectangular region and jut regions, and the base layer is etched by use of the insulating film as a mask to form a base mesa. Consequently, abnormal etching can be prevented from occurring along the base electrode and emitter mesa on the edges of the area where the base electrode and emitter mesa confront each other, and an increase in resistance between the base layer and the emitter layer can be prevented, whereby the bipolar transistor can have enhanced characteristics.

Abstract: A semiconductor device includes a semiconductor substrate of a first conductive type, a collector layer formed on the semiconductor substrate and made of a first semiconductor being of the first conductive type and having a higher resistance than that of the semiconductor substrate, an intrinsic base region having a junction surface with the collector layer and made of a second semiconductor of a second conductive type, and an emitter region having a junction surface with the intrinsic base region and made of a third semiconductor of the first conductive type. A periphery of the intrinsic base region is surrounded by an insulating region extending from the collector layer to the semiconductor substrate.

Abstract: As external connection terminals for an emitter electrode (12) of an IGBT chip, a first emitter terminal (151) for electrically connecting a light emitter in a strobe light control circuit to the emitter electrode (12) and a second emitter terminal (152) for connecting a drive circuit for driving an IGBT device to the emitter electrode (12) are provided. The first emitter terminal (151) and the second emitter terminal (152) are individually connected to the emitter terminal (12) by wire bonding.

Abstract: Apparatus comprising: a first compound semiconductor composition layer doped to have a first charge carrier polarity; a second compound semiconductor composition layer doped to have a second charge carrier polarity and located on the first layer; a third compound semiconductor composition layer doped to have the first charge carrier polarity and located on the second layer; a base electrode on the second layer; and a spacer ring interposed between and defining a charge carrier access path distance between the base electrode and the third layer, the path distance being within a range of between about 200 ? and about 1000 ?. Techniques for making apparatus. Apparatus is useful as a heterobipolar transistor, particularly for high frequency applications.

Abstract: A bipolar transistor in a monocrystalline semiconductor substrate (101), which has a first conductivity type and includes a surface layer (102) of the opposite conductivity type. The transistor comprises an emitter contact (110) on the surface layer; a base contact (130 and 131) extending through a substantial portion (141) of the surface layer, spaced apart (140a) from the emitter; an insulator region (150/151) buried under the base contact; a collector contact (120); and a first polycrystalline semiconductor region (152/153) selectively located under the insulator region, and a second polycrystalline semiconductor region (154) selectively located under the collector contact. These polycrystalline regions exhibit heavy dopant concentrations of the first conductivity type; consequently, they lower the collector resistance.

Abstract: A transistor and a method of fabricating the same: The transistor includes an isolation layer disposed in a semiconductor substrate to define an active region. A pair of source/drain regions is disposed in the active region, spaced apart from each other. A channel region is interposed between the pair of the source/drain regions. The active region has a mesa disposed across the channel region. The mesa extends to the source/drain regions. A gate electrode is disposed to cross the active region along the direction across the mesa.

Abstract: A method for manufacturing a semiconductor device includes forming a buried layer of a semiconductor substrate. An active region is formed adjacent at least a portion of the buried layer. A first isolation structure is formed adjacent at least a portion of the buried layer. A second isolation structure is formed adjacent at least a portion of the active region. A base layer is formed adjacent at least a portion of the active region. A dielectric layer is formed adjacent at least a portion of the base layer, and then at least part of the dielectric layer is removed at an emitter contact location and at a sinker contact location. An emitter structure is formed at the emitter contact location. Forming the emitter structure includes etching the semiconductor device at the sinker contact location to form a sinker contact region. The sinker contact region has a first depth. The method may also include forming a gate structure.

Abstract: A bipolar transistor includes a first layer with a collector. A second layer has a base cutout for a base. A third layer includes a lead for the base. The third layer is formed with an emitter cutout for an emitter. An undercut is formed in the second layer adjoining the base cutout. The base is at least partially located in the undercut. In order to obtain a low transition resistance between the lead and the base, an intermediate layer is provided between the first and the second layer. The intermediate layer is selectively etchable with respect to the second layer. At least in the region of the undercut between the lead and the base, a base connection zone is provided that can be adjusted independent of other production conditions. The intermediate layer is removed in a contact region with the base.

Abstract: A method for forming a metallization layer (30). A first layer (14) is formed outwardly from a semiconductor substrate (10). Contact vias (16) are formed through the first layer (14) to the semiconductor substrate (10). A second layer (20) is formed outwardly from the first layer (14). Portions of the second layer (20) are selectively removed such that the remaining portion of the second layer (20) defines the layout of the metallization layer (30) and the contact vias (16). The first and second layers (14) and (20) are electroplated by applying a bi-polar modulated voltage having a positive duty cycle and a negative duty cycle to the layers in a solution containing metal ions. The voltage and surface potentials are selected such that the metal ions are deposited on the remaining portions of the second layer (20). Further, metal ions deposited on the first layer (14) during a positive duty cycle are removed from the first layer (14) during a negative duty cycle.

Abstract: A bipolar transistor of the present invention comprises a collector layer made of an n-type semiconductor and an emitter layer made of an n-type semiconductor provided on this collector layer. A gate layer for injecting p-type carriers (holes) into the emitter layer is provided on the emitter layer. A p-type carrier retaining layer is formed between the collector layer and the emitter layer. The p-type carrier retaining layer temporarily retains the p-type carriers that are injected from the gate layer into the emitter layer and diffused in the emitter layer and reach the p-type carrier retaining layer. The bipolar transistor has a structure whose performance is not influenced by sheet resistance of the base layer, and is able to exhibit a high current gain even in a high-frequency region.

Abstract: A substrate has a collector region of a first conductivity type, and a base layer of a single crystalline structure and including impurities of a second conductivity type is located over the collector region. An emitter region is defined at least in part by impurities of the first conductivity type contained in the base layer. An emitter electrode of the first conductivity type contacts the emitter region, and at least a portion of the emitter electrode which is in contact with the emitter region has a single crystalline structure.

Abstract: The object of the present invention is to provide a wafer having a structure of enabling an SiC wafer to be put to practical use as a wafer for monitoring a film thickness. For this purpose, an average surface roughness Ra of at least one surface of the SiC wafer is set to be substantially equivalent to a film thickness of a film to be deposited on an Si wafer to be measured. If several types are available to be deposited on an Si wafer to be measured, a minimum film thickness of the film among the several types is determined as an upper limit value, and the average surface roughness Ra of the film thickness measuring SiC wafer is set less than the upper limit value. More concretely, the surface roughness is set to be about 400 times as large as the average surface roughness of a product Si wafer, Ra being preferably set to be 0.08 ?m or less.

Abstract: The intrinsic base region of a bipolar transistor is formed to avoid a chemical interaction between the chemicals used in a chemical mechanical polishing step and the materials used to form the base region. The method includes the step of forming a trench in a layer of epitaxial material. After this, a base material that includes silicon and germanium is blanket deposited, followed by the blanket deposition of a layer of protective material. The layer of protective material protects the base material from the chemical mechanical polishing step.

Abstract: A semiconductor device comprises a first base layer of a first conductive type which has a first surface and a second surface; a second base layer of a second conductive type which is formed on the first surface; first and second gate electrodes which are formed by embedding an electrically conductive material into a plurality of trenches via gate insulating films, the plurality of trenches being formed such that bottoms of the trenches reach the first base layer; source layers of the first conductive type which are formed on a surface area of the second base layer so as to be adjacent to both side walls of the trench provided with the first gate electrode and one side wall of the trench provided with the second gate electrode, respectively; an emitter layer of the second conductive type which is formed on the second surface; emitter electrodes which are formed on the second base layer and the source layers; a collector electrode which is formed on the emitter layer; and first and second terminals which are e

Abstract: A compact ESD protection device is described that uses the reverse breakdown voltage of a base-emitter junction as a trigger diode to switch a transistor that shunts the forward bias ESD current to ground. The trigger diode in series with a leakage diode provides a path to shunt the reverse bias ESD current to ground. The leakage diode is matched to the trigger diode to shunt any leakage current from the trigger diode to ground.

Abstract: The gist of the present invention is as follows: In a monolithic microwave integrate circuit (MMIC) using a heterojunction bipolar transistor (HBT), via holes are respectively formed from the bottom of the MMIC for the emitter, base and collector. Of the via holes, one is located so as to face the HBT. The respective topside electrodes for the other via holes located so as not to face the HBT are provided in contact with the MMIC substrate.

Abstract: Bipolar transistors and methods for fabricating bipolar transistors are disclosed wherein an emitter-base dielectric stack is formed between emitter and base structures, comprising a carbide layer situated between first and second oxide layers. The carbide layer provides an etch stop for etching the overlying oxide layer, and the underlying oxide layer provides an etch stop for etching the carbide layer to form an emitter-base contact opening.

Abstract: In a method of producing a bipolar transistor, a semiconductor substrate having a substrate surface is provided. A base-terminal layer for providing a base terminal is formed on the substrate surface, and an emitter window having a wall area is formed in the base-terminal layer. A first spacing layer is formed on the wall area of the emitter contact window, and a recess is etched into the substrate within a window specified by the first spacing layer. A base layer contacted by outdiffusion from the base-terminal layer is formed in the recess of the emitter window, and a second spacing layer is formed on the first spacing layer and on the base layer. The second spacing layer is structured for the purpose of specifying a planar terminal pad on the base layer, and an emitter layer is formed on the planar terminal pad.

Abstract: The present invention relates to a bipolar transistor of NPN type implemented in an epitaxial layer within a window defined in a thick oxide layer, including an opening formed substantially at the center of the window, this opening penetrating into the epitaxial layer down to a depth of at least the order of magnitude of the thick oxide layer, an N-type doped region at the bottom of the opening, a first P-type doped region at the bottom of the opening, a second lightly-doped P-type region on the sides of the opening, and a third highly-doped P-type region in the vicinity of the upper part of the opening, the three P-type regions being contiguous and forming the base of the transistor.