A semiconductor device includes a field-effect transistor (FET) having a source/drain (S/D) structure and an interconnect structure in contact with the S/D structure. The interconnect structure has a barrier film at a surface of the interconnect structure separating the interconnect structure from materials surrounding the interconnect structure. A first portion of the barrier film covers a first interface between the interconnect structure and the S/ID structure. A second portion of the barrier film covers a second interface between the interconnect structure and dielectric materials adjacent to the interconnect structure. The first portion of the barrier film is thicker than the second portion of the barrier.