Oxygen-free replacement liner for improved transistor performance

An integrated circuit comprising:

• a transistor formed over a substrate;
• a dielectric region formed over the transistor and the substrate;
• a trench positioned in the dielectric region and over a source or drain (S/D) region of the transistor, wherein a sidewall of the trench comprises a gate structure of the transistor;
• a first liner and a conductive plug within the trench such that the first liner and the conductive plug are only present within a bottom portion of the trench;
• and
• a replacement liner and a S/D contact within a top portion of the trench such that a bottom contact surface of the S/D contact directly couples to a top surface of the conductive plug;
• wherein the replacement liner functions as a sidewall spacer for a portion of the gate structure.