Structures for spacers in a device structure for a field-effect transistor and methods for forming spacers in a device structure for a field-effect transistor. A first spacer is located adjacent to a vertical sidewall of a gate electrode, a second spacer located between the first spacer and the vertical sidewall of the gate electrode, and a third spacer located between the second spacer and the vertical sidewall of the gate electrode. The first spacer has a higher dielectric constant than the second spacer. The first spacer has a higher dielectric constant than the third spacer. The third spacer has a lower dielectric constant than the second spacer.