Contact structure of semiconductor device

摘要

The embodiments described above provide mechanisms of forming contact structures with low resistance. A strained material stack with multiple sub-layers is used to lower the Schottky barrier height (SBH) of the conductive layers underneath the contact structures. The strained material stack includes a SiGe main layer, a graded SiG layer, a GeB layer, a Ge layer, and a SiGe top layer. The GeB layer moves the Schottky barrier to an interface between GeB and a metal germanide, which greatly reduces the Schottky barrier height (SBH). The lower SBH, the Ge in the SiGe top layer forms metal germanide and high B concentration in the GeB layer help to reduce the resistance of the conductive layers underneath the contact structures.

主权项

1. A semiconductor device structure, comprising:
a gate structure formed over a surface of a semiconductor substrate; a recess neighboring the gate structure, wherein the recess is formed below the surface of the semiconductor substrate; a strained material stack filling the recess, wherein lattice constants of materials in the strained material stack are different from a lattice constant of the substrate, wherein the strain material stack comprises a boron-doped (B-doped) germanium (GeB) layer, a metal-Ge layer, and a metal-SiGe layer; and a contact structure formed in an inter-layer dielectric (ILD) layer, wherein bottom portion of the contact structure contacts the metal-SiGe layer.