Described herein are integrated circuit devices with source and drain (S/D) contacts with barrier regions. The S/D contacts conduct current to and from semiconductor devices, e.g., to the source and drain regions of a transistor. The barrier regions are formed between the S/D region and an inner conductive structure and reduce the Schottky barrier height between the S/D region and the contact. The barrier regions may include one or more carbon layers and one or more metal layers. A metal layer may include niobium, tantalum, aluminum, or titanium.