Abstract: A gate of an integrated circuit field effect transistor is fabricated by fabricating a gate insulating layer on an integrated circuit substrate, fabricating a metal nitride layer on the gate insulating layer, annealing the metal nitride layer in a nitridizing ambient and fabricating a cap on the metal nitride layer that has been annealed. Thereafter, the cap on the metal nitride layer may be etched to expose sidewalls thereof and another anneal in a nitridizing ambient may take place. Related integrated circuit field effect transistors are also described.

Abstract: A gate of an integrated circuit field effect transistor is fabricated by fabricating a gate insulating layer on an integrated circuit substrate, fabricating a metal nitride layer on the gate insulating layer, annealing the metal nitride layer in a nitridizing ambient and fabricating a cap on the metal nitride layer that has been annealed. Thereafter, the cap on the metal nitride layer may be etched to expose sidewalls thereof and another anneal in a nitridizing ambient may take place. Related integrated circuit field effect transistors are also described.

Abstract: Field effect transistors include a semiconductor substrate of first conductivity type having a surface. A tub region of second conductivity type is in the semiconductor substrate at the surface and extends into the semiconductor substrate a first depth from the first surface. Spaced apart source and drain regions of the second conductivity type are included in the tub region of second conductivity type at the surface, to define single conductivity junctions of the second conductivity type with the tub region of second conductivity type. The spaced apart source and drain regions extend into the tub region a second depth that is less than the first depth. A trench is included in the tub region, between the spaced apart source and drain regions, and extending from the surface into the tub region to a third depth that is more than the second depth but is less than the first depth. An insulated gate electrode is included in the trench.

Abstract: An offset drain Fermi-threshold field effect transistor (Fermi-FET) includes spaced apart source and drain regions in an integrated circuit substrate, and a Fermi-FET channel in the integrated circuit substrate, between the spaced apart source and drain regions. A gate insulating layer is on the integrated circuit substrate between the spaced apart source and drain regions, and a gate electrode is on the gate insulating layer. The gate electrode is closer to the source region than to the drain region. Stated differently, the drain region is spaced farther away from the gate electrode than the source region. The offset drain Fermi-FET can introduce a drift region between the drain region and the Fermi-FET channel that can provide the high voltage and/or high frequency Fermi-FETs, while retaining the Fermi-FET advantages in the channel.

Abstract: A Fermi-FET includes a drain field termination region between the source and drain regions, to reduce and preferably prevent injection of carriers from the source region into the channel as a result of drain bias. The drain field terminating region prevents excessive drain induced barrier lowering while still allowing low vertical field in the channel. The drain field terminating region is preferably embodied by a buried counterdoped layer between the source and drain regions, extending beneath the substrate surface from the source region to the drain region. The buried counterdoped layer may be formed using a three tub structure which produces three layers between the spaced apart source and drain regions. The drain field terminating region may also be used in a conventional MOSFET. The channel region is preferably formed by epitaxial deposition, so that the channel region need not be counterdoped relative to the drain field terminating region.

Abstract: A Fermi-threshold field effect transistor includes spaced-apart source and drain regions which extend beyond the Fermi-tub in the depth direction and which may also extend beyond the Fermi-tub in the lateral direction. In order to compensate for the junction with the substrate, the doping density of the substrate region is raised to counteract the shared charge. Furthermore, the proximity of the source and drain regions leads to a potential leakage due to the drain field which can be compensated for by reducing the maximum tub depth compared to a low capacitance Fermi-FET and a contoured-tub Fermi-FET while still satisfying the Fermi-FET criteria. The tub depth is maintained below a maximum tub depth. Short channel effects may also be reduced by providing source and drain extension regions in the substrate, adjacent the source and drain regions and extending towards the channel regions.

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.

Abstract: A Fermi-FET includes a drain field termination region between the source and drain regions, to reduce and preferably prevent injection of carriers from the source region into the channel as a result of drain bias. The drain field terminating region prevents excessive drain induced barrier lowering while still allowing low vertical field in the channel. The drain field terminating region is preferably embodied by a buried counterdoped layer between the source and drain regions, extending beneath the substrate surface from the source region to the drain region. The buried counterdoped layer may be formed using a three tub structure which produces three layers between the spaced apart source and drain regions. The drain field terminating region may also be used in a conventional MOSFET. The channel region is preferably formed by epitaxial deposition, so that the channel region need not be counterdoped relative to the drain field terminating region.

Abstract: A Fermi-threshold field effect transistor includes a contoured-tub region of the same conductivity type as the source, drain and channel regions and having nonuniform tub depth. The contoured-tub is preferably deeper under the source and/or drain regions than under the channel region. Thus, the tub-substrate junction is deeper under the source and/or drain regions than under the channel region. The diffusion capacitance is thereby reduced compared to a tub having a uniform tub depth, so that a high saturation current is produced at low voltages. The contoured-tub may be formed by an additional implant into the substrate using the gate as a mask.

Abstract: A field effect transistor includes a polycrystalline silicon gate having a semiconductor junction therein. The semiconductor junction is formed of first and second oppositely doped polycrystalline silicon layers, and extends parallel to the substrate face. The polycrystalline silicon gate including the semiconductor junction therein is perfectly formed by implanting ions into the top of the polycrystalline silicon gate simultaneous with implantation of the source and drain regions. The semiconductor junction thus formed does not adversely impact the performance of the field effect transistor, and provides a low resistance ohmic gate contact. The gate need not be masked during source and drain implant, resulting in simplified fabrication.

Abstract: A high current Fermi-FET includes an injector region of the same conductivity type as the Fermi-Tub region and the source and drain regions, located adjacent the source region and facing the drain region. The injector region is preferably doped at a doping level which is intermediate the relatively low doping concentration of the Fermi-Tub and the relatively high doping concentration of the source region. The injector region controls the depth of the carriers injected into the channel and maximizes injection of carriers into the channel at a predetermined depth below the gate. The injector region may also extend to the Fermi-tub depth to decrease bottom leakage current. Alternatively, a bottom leakage current control region may be used to decrease bottom leakage current. Lower pinch-off voltage and increased saturation current are obtained by providing a gate sidewall spacer which extends from adjacent the source injector region to adjacent the sidewall of the polysilicon gate electrode of the Fermi-FET.

Abstract: A field effect transistor includes a polycrystalline silicon gate having a semiconductor junction therein. The semiconductor junction is formed of first and second oppositely doped polycrystalline silicon layers, and extends parallel to the substrate face. The polycrystalline silicon gate including the semiconductor junction therein is perfectly formed by implanting ions into the top of the polycrystalline silicon gate simultaneous with implantation of the source and drain regions. The semiconductor junction thus formed does not adversely impact the performance of the field effect transistor, and provides a low resistance ohmic gate contact. The gate need not be masked during source and drain implant, resulting in simplified fabrication.

Abstract: A Fermi-FET includes a Fermi-tub region at a semiconductor substrate surface, wherein the Fermi-tub depth is bounded between a maximum tub depth and a minimum tub depth. The Fermi-tub depth is sufficiently deep to completely deplete the Fermi-tub region by the substrate tub junction at the threshold voltage of the field effect transistor, and is also sufficiently shallow to produce a closed inversion injection barrier between the source region and the drain region below the threshold voltage of the Fermi-FET. High saturation current and low leakage current are thereby produced simultaneously. Source and drain injector regions and a gate sidewall spacer may also be provided.