Showing papers on "Drain-induced barrier lowering published in 1996"

Power dissipation analysis and optimization of deep submicron CMOS digital circuits

Abstract: This paper introduces a simple analytical model for estimating standby and switching power dissipation in deep submicron CMOS digital circuits. The model is based on Berkeley Short-Channel IGFET model and fits HSPICE simulation results well. Static and dynamic power analysis for various threshold voltages is addressed. A design methodology to minimize the power-delay product by selecting the lower and upper bounds of the supply and threshold voltages is presented. The effects of the supply voltage, the threshold voltage, and /spl eta/, which reflects the drain induced barrier lowering, are also addressed.

Feedback loop for reading threshold voltage

Abstract: To read the threshold voltage of a transistor such as a floating gate transistor in an analog or multi-level memory cell, the transistor is connected in a feedback loop which contains a differential amplifier having an output terminal and an input terminal respectively connected to the gate and a node (source or drain) of the transistor. A reference voltage is asserted to a second input terminal of the differential amplifier. A load provides a current which charges the node, and the differential amplifier adjusts the gate voltage of the memory cell to an equilibrium value where current through the transistor is equal to current through the reference cell. The equilibrium value of the gate voltage depends on and indicates the threshold voltage of the transistor. In one embodiment of the invention, the load is a current source which mirrors a current through a reference cell that is structurally identical to the transistor, and the drain of the reference cell provides the reference voltage to the amplifier.

Method of making thin film transistor using lateral crystallization

Abstract: A highly reliable thin-film transistor (TFT) having excellent characteristics. A silicon film is grown laterally by adding a metal element such as nickel to promote crystallization. A crystal grain boundary is formed parallel to a gate electrode and around the center of the gate electrode. Thus, the grain boundary does not exist around the interface between the drain and the channel formation region. At this interface, a large stress is induced by a large electric field. The concentration of the metal element is low around the interface between the drain and the channel formation region. Therefore, the leakage voltage is small. Also, when a reverse voltage is applied to the gate electrode, the leakage current is small.

Punch-through field effect transistor

Abstract: A trenched field effect transistor suitable especially for low voltage power applications provides low leakage blocking capability due to a gate controlled barrier region between the source region (44) and drain region (40). Forward conduction occurs through an inversion region between the source region (44) and drain region (40). Blocking is achieved by a gate controlled depletion barrier. Located between the source (44) and drain (40) regions is a fairly lightly doped body region (42). The gate electrode (52A), located in a trench (50A), extends through the source (44) and body (42) regions and in some cases into the upper portion of the drain region (40). The dopant type of the polysilicon gate electrode (52A) is the same type as that of the body region (42). The body region (42) is a relatively thin and lightly doped epitaxial layer grown upon a higly doped low resistivity substrate of opposite conductivity type. In the blocking state the epitaxial body region is depleted due to applied drain-source voltage, hence a punch-through type condition occurs vertically. Lateral gate control increases the effective barrier to the majority carrier flow and reduces leakage current to acceptably low levels.

Semiconductor device having an insulated gate field effect thin film transistor

Abstract: A channel forming region of a thin-film transistor is covered with an electrode and wiring line that extends from a source line. As a result, the channel forming region is prevented from being illuminated with light coming from above the thin-film transistor, whereby the characteristics of the thin-film transistor can be made stable.

PMOS memory cell with hot electron injection programming and tunnelling erasing

Abstract: A P-channel MOS memory cell has P+ source and drain regions formed in an N-well. A thin tunnel oxide is provided between the well surface and an overlying floating gate. In one embodiment, the thin tunnel oxide extends over a substantial portion of the active region and the device. An overlying control gate is insulated from the floating gate by an insulating layer. The device is programmed via hot electron injection from the drain end of the channel region to the floating gate, without avalanche breakdown, which allows the cell to be bit-selectable during programming. Erasing is accomplished by electron tunneling from the floating gate to the N-well with the source, drain, and N-well regions equally biased. Since there is no high drain/well junction bias voltage, the channel length of the cell may be reduced without incurring and destructive junction stress.

Multiple implant lightly doped drain (MILDD) field effect transistor

Abstract: A multiple implant lightly doped drain ("MILDD") field effect transistor is disclosed. The transistor includes a channel, a gate, a dielectric structure that separates the gate from the channel, a source region and a drain region. The drain region has a first drain subregion, a second drain subregion and a third drain subregion. Each drain subregion has a dopant concentration that differs from that of the other two drain subregions. A method of forming the same is also disclosed.

Method for manufacturing a vertical transistor having a storage node vertical transistor

Abstract: A method for manufacturing a three-dimensionally structured vertical transistor or memory cell including the steps of forming a silicon-on-insulator (SOI) structure on a semiconductor substrate, sequentially depositing a drain region, a channel region and a source region on the SOI substrate structure, a cylinder-type gate insulation layer surrounding the channel region and a gate electrode surrounding the gate insulation layer, to thereby increase the integration of a device. This process and structure avoids the characteristic degradation caused by the leakage current associated with the trench process and structure.

Asymmetric low power MOS devices

Abstract: Low threshold voltage MOS devices having asymmetric halo implants are disclosed herein. An asymmetric halo implant provides a pocket region located under a device's source or drain near where the source (or drain) edge abuts the device's channel region. The pocket region has the same conductivity type as the device's bulk (albeit at a higher dopant concentration) and, of course, the opposite conductivity type as the device's source and drain. Only the source or drain, not both, have the primary pocket region. An symmetric halo device behaves like two pseudo-MOS devices in series: a "source FET" and a "drain FET." If the pocket implant is located under the source, the source FET will have a higher threshold voltage and a much shorter effective channel length than the drain FET.

FET having gate insulating film of nonuniform thickness and asymmetrical source and drain structures

Abstract: A high withstand voltage transistor and a method for manufacturing the same are disclosed. The transistor includes a semiconductor substrate, a field oxide film, a channel region formed of first and second channel regions each having a different concentration level, a gate insulating film having a step difference, a gate electrode having a step difference, a drain region including first, second, and third impurity regions, a source region including first and third impurity regions, a spacer, an interlayer dielectric film and a metal electrode. Threshold voltage can be maintained to an appropriate level, junction break voltage can be increased, and the punchthrough characteristic can also be enhanced.

Method of fabricating a raised source/drain MOSFET using self-aligned POCl3 for doping gate/source/drain regions

Abstract: A MOSFET design is provided that utilizes raised poly source/drain regions in a novel manner, thereby reducing the problems associated with conventional MOSFET designs, including the "short channel effect." The "short channel effect" is reduced by forming the N+ junction inside the N- LDD diffusion by outdiffusing from the overlying doped poly. Junctions are formed from doped poly using a POCl3 source self-aligned to the gate, source and drain regions, and RTA to drive dopant from the poly into the silicon substrate. Since the raised poly source/drain regions extend over field oxide, the source/drain junction areas are much smaller; parasitic capacitances are greatly reduced and device speed is enhanced. The process results in low resistivity compared to conventional techniques, even without the use of salicide. Since there is no gate implantation, there is a reduced risk of damage to the gate oxide.

Biasing circuit for reducing body effect in a bi-directional field effect transistor

Abstract: A field effect transistor (FET) includes a first source/drain terminal, a body terminal, and a second source/drain terminal. A bi-directional N-channel FET circuit includes a biasing circuit which couples the body terminal of the bi-directional FET to one of its first and second source/drain terminals having a lesser voltage when the first and second source/drain voltages differ by more than a threshold voltage. When the voltages differ by a threshold voltage or less, the body terminal floats at a voltage no higher than a diode drop above the lesser of the two source/drain voltages, and at a voltage no lower than a threshold voltage below the higher of the two source/drain voltages. An analogous bi-directional P-channel FET circuit is also described. Body effect is reduced because the body terminal of the FET is maintained at a voltage at or near the voltage of the effective source terminal at all times, irrespective of which of the two source/drain terminals is the effective source terminal. Consequently, the ON-resistance of the FET is reduced.

Semiconductor memory device having negative resistance element operated stably with single low power source

Abstract: A memory cell of an SRAM includes an access transistor, and an MIS switching diode. The access transistor has a drain electrode connected to a bit line of a corresponding column, a source electrode connected to a storage node, and a gate electrode connected to a word line of a corresponding row. The threshold voltage of the access transistor is small than the threshold voltage of a bit line load transistor. The MIS switching diode is connected between the storage node and a second power supply potential node. The switching initiate voltage of the MIS switching diode is greater than the difference between the first potential and the threshold voltage of the bit line load transistor, and smaller than the difference between the first potential and the threshold voltage of the access transistor. Thus, data can be read/written and held accurately.

Thin-film transistor circuit and image display

Abstract: A thin-film transistor circuit, which is used as a driving circuit for driving pixels in an image display, is constituted of a plurality of thin-film transistors that are formed on an insulating substrate. In each thin-film transistor, a conductive electrode is placed so as to face a gate electrode with a channel region of a polycrystal silicon thin-film that forms an active layer located in between. Here, a constant voltage is applied to the conductive electrode. When threshold voltage is shifted by applying a voltage to the conductive electrode, it is possible to allow the absolute value of the threshold voltage of n-channel-type transistors and the absolute value of the threshold voltage of p-channel-type transistors to become virtually equal to each other. Moreover, it is possible to properly set the threshold voltage in accordance with factors such as the channel length of the thin-film transistors, the types of circuits that are constituted of the thin-film transistors and voltages to be applied to the thin-film transistors. Thus, it becomes possible to remarkably improve the characteristics of thin-film transistor circuits, such as operation speeds and holding characteristics.

On the threshold voltage and channel conductance of polycrystalline silicon thin‐film transistors

Abstract: A model for the grain‐boundary barrier height of undoped polycrystalline silicon thin‐film transistors is developed based on a rodlike structure of the grains with a square cross section and a Gaussian energy distribution of the trapping states at the grain boundaries. An analytical expression for the threshold voltage is derived in terms of the distribution parameters of the grain‐boundary trapping states, the grain size, and the gate oxide thickness. Comparison between the developed model and the experimental drain current versus gate voltage data has been made and excellent agreement was obtained. The key parameters affecting the threshold voltage and the channel conductance of the transistor were investigated by computer stimulation. The threshold voltage is mainly affected by the grain size and the gate oxide thickness. For the improvement of the channel conductance, besides the passivation of the grain‐boundary trapping states, the increase of the grain size and mainly the scaling down of the gate o...

Level shift semiconductor device

Abstract: A level shift semiconductor device converts a signal level into another level between circuits connected to each other having different supply voltages. An input signal is supplied to the source of a first MOS transistor of a first-conductivity type (NMOS). The drain of the 1st NMOS transistor is connected to the input terminal of an inverter. An output signal is outputted via the output terminal of the inverter. The drain and gate of a first MOS transistor of a second-conductivity type (PMOS) are connected to the input and output terminals of the inverter, respectively. The gate and source of a second NMOS transistor are connected to the output terminal of the inverter and the gate of the 1st NMOS transistor, respectively. The gate and source of a second PMOS transistor are connected to the gate and source of the 2nd NMOS transistor. A first supply voltage is supplied to the drain of the 2nd PMOS transistor. And, a second supply voltage is supplied to the inverter, the source of the 1st PMOS transistor, and the drain of the 2nd NMOS transistor. The second voltage is larger in absolute value than the first voltage.

Flash memory including improved transistor cells and a method of programming the memory

Abstract: A flash memory includes a plurality of MOSFETs. Each of the MOSFETs comprises a first conductive type substrate, a source, and a drain. The source and the drain are formed on one major surface of the substrate. A floating gate is situated over the major surface via a first insulation layer in a manner to control a current flowing through a channel between the source and the drain. The floating gate is highly resistive so as to essentially hold electrons in the region into which they were are injected from a depletion layer formed in the channel. A control gate is further provided over the floating gate via a second insulation layer.

Method of forming isolation regions in a MOS transistor device

Abstract: The present invention is directed to a MOS transistor and its method of fabrication. The transistor includes isolating layers below source/drain regions of the transistor. In this manner, lateral diffusion occurring in the source/drain regions can be retarded. Accordingly, the fabricated. MOS transistor has the advantages of shallow junction depth, low junction capacitance, and better punchthrough resistance. Furthermore, since the bulk of the MOS transistor might be connected to a constant voltage, most likely ground, via a contact region, the floating body effects typically encountered in SOI (silicon-on-insulator) devices can be avoided.

Liquid crystal display device having uniform parasitic capacitance between pixels

Abstract: A liquid crystal display device according to the present invention includes pixels having uniform parasitic capacitance values. Each pixel comprises at least one thin film transistor. The gate electrode of the thin film transistor is formed from part of a gate line, so as to reduce the overall area occupied by the transistor. A drain electrode is formed over and within the width of the gate line and parallel to the source electrode, and having a surface area less than the underlying portion of the gate line. In addition, the source electrode and the drain electrode are isolated, but electrically connected to a semiconductor layer, from the gate electrode. A drain electrode extension is connected with the drain electrode and a pixel electrode, and projects outward over both width edges of the gate line. The drain electrode and drain electrode extension are dimensioned with sufficient margins with respect to the gate line to account for misalignments between the drain electrode and the gate line. In this way, the difference in pixel brightness due to differences in parasitic capacitance is removed by eliminating the possibility of alignment errors from varying the parasitic capacitance between pixels. Moreover, the area which the thin film transistor occupies is respectively widened compared with the prior art and the number of corrections to be made on each wiring layer is decreased because the cross steps of the gate electrode and the source electrode that occur on the underlying layer are reduced.

Lateral high-voltage DMOS transistor with drain zone charge draining

Abstract: In many circuits in which a current is switched off, a high voltage appears at the drain electrode of a transistor, in particular in the case of an inductive load. When a lateral high-voltage DMOST is used, such a high voltage may lead to instability in the transistor characteristics or may even damage the transistor. To avoid this problem, the drain of a high-voltage LDMOST is locally provided with a strongly doped n-type zone 18, 21 (in the case of an n-channel transistor) which extends, seen from the surface, down into the semiconductor body to a greater depth than does the source zone 8, so that a pn-junction is formed at a comparatively great depth in the semiconductor body having a breakdown voltage that is lower than the BV ds of the transistor without this zone. The energy stored in the inductance may thus be drained off through breakdown of the pn-junction. This breakdown is separated from the normal current path of the transistor owing to the comparatively great depth of the pn-junction, so that the robustness of the transistor is improved. This deep zone in the drain may be formed, for example, by a buried layer at the boundary between an epitaxial layer and the substrate.

High-swing cascode current mirror

Abstract: A high-swing current mirror includes a cascode current source and a current source bias circuit. The current source includes first and second bias terminals and an output terminal. The bias circuit includes transistors M1, M2A, M2B and M3A. Transistor M1 has a gate, source, and drain, with the gate coupled to the drain. Transistor M2A has a gate, source, and drain, with the gate and source of transistor M2A coupled to the gate and source, respectively, of transistor M1. Transistor M2B has a gate and drain coupled to one another and to the second bias terminal and a source coupled to the drain of transistor M2A. Transistor M3A has a gate and drain coupled together and to the first bias terminal and a source coupled to the sources of transistors M1 and M2A. The transistors in the cascode current source and current source bias circuit have ratios of device transconductance parameters such that the cascode current source remains in saturation to provide the highest possible voltage swing at the output terminal.

Power semiconductor structure with lateral transistor driven by vertical transistor

Abstract: A power semiconductor structure (200), in particular in VIPower technology, made from a chip of N-type semiconductor material (110), comprising a bipolar or field-effect vertical power transistor (125, 120, 110) having a collector or drain region in such N-type material (110); the semiconductor structure comprises a PNP bipolar lateral power transistor (210, 110, 220) having a base region in such N-type material (110) substantially in common with the collector or drain region of the vertical power transistor.

Charge pump with near zero offset current

Abstract: A charge pump of a phase-locked loop includes a first P channel transistor and a first N channel transistor coupled to mirror a current in a constant current source. The P channel transistor and N channel transistor are formed with dimensions that match transient responses of currents through the N and P channel transistors during switching rather than matching the gains of the N and P channel transistors. In one embodiment, the channel length of the N channel transistor is twice a channel length of the P channel transistor. A second P channel transistor and a second N channel transistor connected in series with the first P and N channel transistors switch the current through the first P channel transistor and the first N channel transistor respectively. The second P channel transistor and the second N channel transistor have matched gate-drain capacitances so that they have the same switching speed. A first capacitor coupled between the gate of the first P channel transistor and a supply voltage and a second capacitor coupled between the gate of the first N channel transistor and a reference voltage reduce the effect that jitter in the supply and reference voltages has on the charge pump.

MOS transistor and method for making the same

Abstract: Transistor devices comprise a gate electrode, a channel region formed beneath the gate electrode, a source region in contact with one side of the channel region, a first conductive region formed in a semiconductor layer at the outer side of the source region and made of a metal or metal compound, a drain region formed in contact with the other side of the channel region, and a second conductive region formed in the semiconductor layer at the outer side of the drain region and consisting of a metal or a metal compound. The transistor has an SOI structure which has an improved breakdown voltage between the source region and the drain region with low sheet resistances of the source and drain regions. Methods for making the transistor devices are also described.

Transistor and method for manufacturing the same

Abstract: In a process for manufacturing a thin film transistor having a semiconductor layer constituting source and drain regions and a channel forming region, by the semiconductor layer being made thinner in the source and drain regions than in the channel forming region a structure is realized wherein, at the boundary between the source region and the channel forming region and the boundary between the drain region and the channel forming region, portions where electric field concentrations occur are displaced from the portion where a channel is formed. By reducing the OFF current (the leak current) without also reducing the ON current, a high mutual conductance is realized.

Fermi-threshold field effect transistors including source/drain pocket implants and methods of fabricating same

Abstract: A Fermi-FET, including but not limited to a tub-FET, a contoured-tub Fermi-FET or a short channel Fermi-FET includes a drain extension region of the same conductivity type as the drain region and a drain pocket implant region of opposite conductivity type from the drain region The drain pocket implant region acts as a drain field stop to reduce or prevent drain-to-source field reach-through Reduced low drain field threshold voltage, significantly reduced drain induced barrier lowering and reduced threshold dependence on channel length may be obtained, resulting in higher performance in short channels

Forming a MOS transistor with a recessed channel

Abstract: A MOS transistor is fabricated by forming an inverse gate mask consisting of a lower silicon dioxide layer and an upper silicon nitride layer. The exposed channel region is thermally oxidized. The mask is removed to permit a source/drain implant. The oxide growth is removed so that the channel region is recessed. A differential oxide growth then serves to mask the source and the drain for channel threshold adjust and punch-through implants. A doped polysilicon gate is formed, with the thinner area of the differential oxide serving as the gate oxide. In the resulting structure, the punch-through dopant is spaced from the source and the drain, reducing parasitic capacitance and improving transistor switching speeds.

Raised source/drain MOS transistor with covered epitaxial notches and fabrication method

Abstract: The invention provides a technique for forming a MOS transistor with reduced leakage current and a shorter channel length between source and drain electrodes. The transistor includes a gate electrode between raised source and drain electrodes that are formed from epitaxial silicon. Typically, the raised source and drain electrodes are thin where the intersect the gate electrode so that epitaxial notches are formed between the gate sidewall insulation and the source/drain electrodes. To protect the source/drain junction areas underlying the epitaxial notches from undesired penetration of doping impurities used in the fabrication of the electrodes, the notches are covered with insulation material. In a special process step, performed between forming the epitaxial layers and implanting the layers with dopants to form source and drain electrodes, insulation material is added to the initial, relatively thin, gate sidewalls that insulate the gate electrode from the source/drain electrodes. Any subsequent diffusion of doping impurities into the underlying source/drain junction areas occurs at a uniform rate so that the junction depth beneath the notches is not deeper than other regions of the junction areas. Thin uniform junction areas permit the channel length between source/drain electrodes to be shortened so that transistors may be packed more densely on a substrate. A raised source/drain MOS transistor with gate insulation sidewalls to fill epitaxial notches is also provided.

Starting circuit and method for starting a MOS transistor

Abstract: A start up circuit causes a MOS transistor to be turned on by sensing local electrical quantities thereof, specifically the potential at the drain terminal of the MOS transistor. A small current is injected into the control terminal of the MOS transistor when the potential at the drain terminal is high. For the purpose, an electric network is arranged to couple these two terminals together.