US Patent 9257531 Self-aligned contact structure for replacement metal gate

A metallic top surface of a replacement gate structure is oxidized to convert a top portion of the replacement gate structure into a dielectric oxide. After removal of a planarization dielectric layer, selective epitaxy is performed to form a raised source region and a raised drain region that extends higher than the topmost surface of the replacement gate structure. A gate level dielectric layer including a first dielectric material is deposited and subsequently planarized employing the raised source and drain regions as stopping structures. A contact level dielectric layer including a second dielectric material is formed over the gate level dielectric layer, and contact via holes are formed employing an etch chemistry that etches the second dielectric material selective to the first dielectric material. Raised source and drain regions are recessed. Self-aligned contact structures can be formed by filling the contact via holes with a conductive material.