Techniques are disclosed for forming transistor devices having reduced parasitic contact resistance relative to conventional devices. The techniques can be implemented, for example, using a standard contact stack such as a series of metals on, for example, silicon or silicon germanium (SiGe) source/drain regions. In accordance with one example such embodiment, an intermediate boron doped germanium layer is provided between the source/drain and contact metals to significantly reduce contact resistance. Numerous transistor configurations and suitable fabrication processes will be apparent in light of this disclosure, including both planar and non-planar transistor structures (e.g., FinFETs), as well as strained and unstrained channel structures. Graded buffering can be used to reduce misfit dislocation. The techniques are particularly well-suited for implementing p-type devices, but can be used for n-type devices if so desired.

Techniques are disclosed for forming transistor devices having source and drain regions with high concentrations of boron doped germanium. In some embodiments, an in situ boron doped germanium, or alternatively, boron doped silicon germanium capped with a heavily boron doped germanium layer, are provided using selective epitaxial deposition in the source and drain regions and their corresponding tip regions. In some such cases, germanium concentration can be, for example, in excess of 50 atomic % and up to 100 atomic %, and the boron concentration can be, for instance, in excess of 1E20 cm.sup.3. A buffer providing graded germanium and/or boron concentrations can be used to better interface disparate layers. The concentration of boron doped in the germanium at the epi-metal interface effectively lowers parasitic resistance without degrading tip abruptness. The techniques can be embodied, for instance, in planar or non-planar transistor devices.

Techniques are disclosed for forming transistor devices having reduced parasitic contact resistance relative to conventional devices. The techniques can be implemented, for example, using a standard contact stack such as a series of metals on, for example, silicon or silicon germanium (SiGe) source/drain regions. In accordance with one example such embodiment, an intermediate boron doped germanium layer is provided between the source/drain and contact metals to significantly reduce contact resistance. Numerous transistor configurations and suitable fabrication processes will be apparent in light of this disclosure, including both planar and non-planar transistor structures (e.g., FinFETs), as well as strained and unstrained channel structures. Graded buffering can be used to reduce misfit dislocation. The techniques are particularly well-suited for implementing p-type devices, but can be used for n-type devices if so desired.

A method of making a graphene base transistor with reduced collector area comprising forming an electron injection region, forming an electron collection region, and forming a base region wherein the base region comprises one or more sheets of graphene and wherein the base region is intermediate the electron injection region and the electron collection region and forms electrical interfaces therewith.

Techniques are disclosed for forming transistor devices having source and drain regions with high concentrations of boron doped germanium. In some embodiments, an in situ boron doped germanium, or alternatively, boron doped silicon germanium capped with a heavily boron doped germanium layer, are provided using selective epitaxial deposition in the source and drain regions and their corresponding tip regions. In some such cases, germanium concentration can be, for example, in excess of 50 atomic % and up to 100 atomic %, and the boron concentration can be, for instance, in excess of 1E20 cm.sup.3. A buffer providing graded germanium and/or boron concentrations can be used to better interface disparate layers. The concentration of boron doped in the germanium at the epi-metal interface effectively lowers parasitic resistance without degrading tip abruptness. The techniques can be embodied, for instance, in planar or non-planar transistor devices.

A method of making a graphene base transistor with reduced collector area comprising forming a graphene material layer, forming a collector material, depositing a dielectric, planarizing the dielectric, cleaning and removing the native oxide, transferring a base graphene material layer to the top surface of the graphene material layer, bonding the base graphene material layer, and photostepping and defining a second graphene material layer. A method of making a graphene base transistor with reduced collector area comprising forming an electron injection region, forming an electron collection region, and forming a base region. A graphene base transistor with reduced collector area comprising an electron emitter region, an electron collection region, and a base region.

In one aspect, a transistor comprises a metal emitter, a first semiconductor barrier, a metal base, a second semiconductor barrier, and a metal collector. The first semiconductor barrier separates the metal emitter and the metal base and has an average thickness based on a first mean free path of a charge carrier in the first semiconductor barrier emitted from the metal emitter. The second semiconductor barrier separates the metal base from the metal collector and has an average thickness based on a second mean free path of the charge carrier in the second semiconductor barrier injected from the metal base. The metal base comprises two or more metal layers and has an average thickness based on a multi-layer mean free path of the charge carrier.

A fin-based tunneling filed field effect transistor (TFET) includes a control gate structure and an assisting gate structure adjacent to the control gate structure. The assisting gate structure is disposed between the control gate structure and a source/drain region of the fin-based TFET. When a voltage is applied to the assisting gate structure, the assisting gate structure causes the valence band of the fin-based TFET to be raised near the junction between the source/drain region and a channel region in a semiconductor layer under the assisting gate structure. This reduces the tunneling distance between the source/drain region and the channel region, which allows for a lesser threshold voltage to be used for the control gate structure than without the assisting gate structure.