A semiconductor device includes a substrate, a source/drain feature, a gate structure, a top interlayer dielectric (ILD), a contact, and an isolation pillar. The source/drain feature is at least partially disposed in the substrate. The gate structure is disposed on the substrate and adjacent to the source/drain feature. The top ILD is disposed on the gate structure. The contact is disposed on the source/drain feature. The contact includes a barrier metal and a contact metal. The barrier metal is disposed on and in contact with the source/drain feature. The contact metal is disposed on the barrier metal. The isolation pillar is disposed adjacent to the contact. The isolation pillar is in contact with the barrier metal and the contact metal of the contact and the top ILD.