To maintain the scaling trends in the complementary metal oxide semiconductor (CMOS) technology, the thickness of barrier/liner systems used in back-end-of-line (BEOL) fabrication of metal interconnects needs to be sub-2 nm. However, reducing the thickness of the traditional barrier and liner systems necessary for the dimensional scaling of future interconnects is extremely challenging. Hence, ultrathin two-dimensional (2D) transition-metal dichalcogenide (TMD) films can be an alternative to current barrier/liner systems. However, the processes used to grow these films are generally not BEOL-compatible. Here, using the plasma-free metal–organic chemical vapor deposition (MOCVD) process, we grow BEOL-compatible tungsten disulfide (WS₂) film, which has a clear advantage over current diffusion barrier/liner systems used in Cu-interconnects. Our results show that these WS₂ films not only block Cu diffusion but also reduce the effective resistance of the Cu film by suppressing the grain boundary and interface scattering of electrons.