Semiconductor Contact Plug Formation Using Germanium Epitaxial Layer

The patent applies preliminary action by forming the contact plug structure before the metal gate structure in a reversed sequence. Specifically, the method forms a contact hole through the interlayer dielectric to expose the source/drain region, forms a contact plug, then forms the metal gate structure over the contact plug. This reversed sequence prevents position shift penetration issues because the contact plug is established first as a reference, and subsequent metal gate formation cannot penetrate through the already-formed contact plug structure.

The patent applies inversion by completely reversing the conventional formation sequence of contact plugs and metal gates. Instead of forming contact plugs after metal gates, the method forms contact plugs first, then forms metal gates over them. This inverted sequence fundamentally changes the spatial and temporal relationship between the two structures, eliminating the penetration problem that occurs with continuous dimension shrinkage in conventional processes.

The patent applies the intermediary principle by introducing a germanium layer as a protective mediator between the source/drain region and the subsequent etching processes. The germanium layer is formed via selective epitaxial growth on the source/drain regions, creating a protective barrier that prevents damage during later manufacturing steps. This intermediary layer acts as a buffer that protects the underlying source/drain structures while being removable or integrable into the final device structure.