US Patent 10134633 Self-aligned contact with CMP stop layer

In a self-aligned contact (SAC) process, a sacrificial etch stop layer is embedded over source/drain regions, i.e., directly over an interlayer dielectric (IDL) disposed over source/drain regions to enable polishing of a nitride capping layer with respect to the interlayer dielectric. The sacrificial etch stop layer may comprise cobalt metal, and is adapted to be removed and replaced with additional ILD material after controlled polishing of the nitride capping layer.