Structures that include a field effect-transistor and methods of forming a structure that includes a field-effect transistor. A first field-effect transistor includes a first source/drain region, and a second field-effect transistor includes a second source/drain region. A first contact is arranged over the first source/drain region, and a second contact is arranged over the second source/drain region. A portion of a dielectric layer, which is composed of a low-k dielectric material, is laterally arranged between the first contact and the second contact.