A semiconductor device and a method for fabricating the device are disclosed. The semiconductor device includes a substrate and a dielectric layer formed on the substrate. A trench is formed in the dielectric layer, and a conductive structure is formed in the trench. The conductive structure includes a barrier layer and a metal contact structure. The barrier layer covers a bottom wall of each trench, and the metal contact structure is located on the barrier layer and fills the trench. The metal contact structure is made of a single metal material.

A semiconductor device and a method of fabricating the same including a substrate, a first semiconductor layer, a second semiconductor layer, a first insulating layer, a gate dielectric layer, and a gate structure. The first semiconductor layer extends in a first direction. The second semiconductor layer is disposed on the first semiconductor layer and extends in a second direction, the first direction is perpendicular to the second direction, and the first semiconductor layer and the second semiconductor layer are monolithic. The first insulating layer is disposed on the first semiconductor layer. The gate dielectric layer is disposed on a sidewall of the second semiconductor layer and is partially disposed on the first insulating layer. The gate structure is disposed on the gate dielectric layer. Accordingly, the first semiconductor layer and the second semiconductor layer are formed simultaneously, for serving as the source structure and the channel structure respectively.

Embodiments of semiconductor devices and methods are provided for reducing the resistivity of contact structures used in semiconductor devices. In the disclosed embodiments, an improved silicidation process is used to reduce the contact resistivity between an overlying metal plug and an underlying silicon-containing layer. The improved silicidation process reduces contact resistivity by forming a thin barrier metal silicide on an underlying silicon-containing layer before a thicker metal layer is deposited onto the barrier metal silicide and heated to form a second metal silicide above the barrier metal silicide. The combination of the barrier metal silicide and the second metal silicide provides a metal silicide-to-semiconductor contact between the overlying metal plug and the underlying silicon-containing layer with reduced contact resistivity.

A semiconductor device is provided and includes a substrate, a gate structure and a conductive plug. The gate structure is formed in the substrate and includes a conductive layer and an insulating capping layer. The conductive layer has a first portion and a second portion extending in a vertical direction from the upper surface of the first portion, so that a step height is formed between the upper surface of the first portion and the upper surface of the second portion. The insulating capping layer covers the upper surfaces of the first portion and the second portion.