In certain embodiments, a semiconductor device includes a substrate having an n-doped well feature and an epitaxial silicon germanium fin formed over the n-doped well feature. The epitaxial silicon germanium fin has a lower part and an upper part. The lower part has a lower germanium content than the upper part. A channel is formed from the epitaxial silicon germanium fin. A gate is formed over the epitaxial silicon germanium fin. A doped source-drain is formed proximate the channel.

Disclosed is a FinFET varactor with low threshold voltage and methods of making the same. A disclosed method includes receiving a semiconductor layer over a substrate and having channel, source, and drain regions. The method includes forming a well in the semiconductor layer to have a first dopant, and implanting a second dopant into the well. The first and second dopants are of opposite doping types. A first portion of the well has a higher concentration of the second dopant than the first dopant. A second portion of the well under the first portion has a higher concentration of the first dopant than the second dopant. The method further includes forming a gate stack over the channel region, and forming source and drain features in the source and drain regions. The first portion of the well electrically connects the source and drain features.

Present disclosure provides a FinFET structure, including a fin and a gate surrounding a first portion of the fin. A dopant concentration in the first portion of the fin is lower than about 1E17/cm.sup.3. The FinFET structure further includes an insulating layer surrounding a second portion of the fin. The dopant concentration of the second portion of the fin is greater than about 8E15/cm.sup.3. The insulating layer includes a lower layer and an upper layer, and the lower layer is disposed over a substrate connecting to the fin and has a dopant concentration greater than about 1E19/cm.sup.3.

In accordance with some embodiments, a source/drain contact is formed by exposing a source/drain region through a first dielectric layer and a second dielectric layer. The second dielectric layer is recessed under the first dielectric layer, and a silicide region is formed on the source/drain region, wherein the silicide region has an expanded width.

A gallium-doped sacrificial epitaxial or polycrystalline germanium layer is formed on a silicon germanium substrate having a high percentage of germanium followed by annealing to diffuse the gallium into the silicon germanium substrate. The germanium layer is selectively removed to expose the surface of a gallium-doped silicon germanium region within the silicon germanium substrate. The process has application to the formation of electrically conductive regions within integrated circuits such as source/drain regions and junctions without the introduction of carbon into such regions.

A method of fabricating a FinFET includes at last the following steps. A <551> direction is determined by tilting 8.05±2 degrees from a normal vector of a (110) lattice plane of a semiconductor substrate. The semiconductor substrate is patterned along a lattice plane perpendicular to the <551> direction, so as to form a plurality of trenches in the semiconductor substrate and at least one semiconductor fin having sidewalls disposed on a (551) lattice plane. Insulators are in the trenches. A gate stack is formed over portions of the semiconductor fin and over portions of the insulators. Strained material portions are formed over the semiconductor fins revealed by the gate stack.

Aspects of the present disclosure include fabricating integrated circuit (IC) structures using a boron etch-stop layer, and IC structures with a boron-rich region therein. Methods of forming an IC structure according to the present disclosure can include: growing a conductive epitaxial layer on an upper surface of a semiconductor element; forming a boron etch-stop layer directly on an upper surface of the conductive epitaxial layer; forming an insulator on the boron etch-stop layer; forming an opening within the insulator to expose an upper surface of the boron etch-stop layer; annealing the boron etch-stop layer to drive boron into the conductive epitaxial layer, such that the boron etch-stop layer becomes a boron-rich region; and forming a contact to the boron-rich region within the opening, such that the contact is electrically connected to the semiconductor element through at least the conductive epitaxial layer.

A method for manufacturing a semiconductor device includes forming a fin structure extending in a first direction on a substrate, forming a sacrificial gate pattern extending in a second direction to intersect the fin structure, forming a gate spacer layer covering the fin structure and the sacrificial gate pattern, providing a first ion beam having a first incident angle range and a second ion beam having a second incident angle range to the substrate, patterning the gate spacer layer using the first ion beam and the second ion beam to form gate spacers on sidewalls of the sacrificial gate pattern, forming source/drain regions at both sides of the sacrificial gate patterns, and replacing the sacrificial gate pattern with a gate electrode.

Methodologies for patterning and implantation are provided Embodiments include forming fins; forming an SiN over the fins; forming an a-Si layer over the SiN; forming and patterning a first patterning layer over the a-Si layer; etching through the a-Si layer using the first patterning layer as a mask; removing the first patterning layer; implanting ions in exposed groups of fins; forming and patterning a second patterning layer to expose a first group of fins and a portion of the a-Si layer on opposite sides of the first group of fins; implanting ions in a first region of the first group of fins; forming a third patterning layer over the first region of the first group of fins and exposing a second region of the first group of fins; and implanting ions in the second region of the first group of fins.

Various embodiments include methods and integrated circuit structures. In some cases, a method of forming an integrated circuit structure can include: forming a mask over an oxide layer and an underlying set of fin structures, the set of fin structures including a plurality of fins each having a substrate base and a silicide layer over the substrate base; implanting the oxide layer through an opening in the mask; removing the mask; polishing the oxide layer overlying the set of fin structures after removing the mask to expose the set of fin structures; and forming a nitride layer over the set of fin structures.