A semiconductor device structure, along with methods of forming such, are described. The structure includes a substrate, a source/drain contact disposed over the substrate, a first dielectric layer disposed on the source drain contact, an etch stop layer disposed on the first dielectric layer, and a source/drain conductive layer disposed in the etch stop layer and the first dielectric layer. The structure further includes a spacer structure disposed in the etch stop layer and the first dielectric layer. The spacer structure surrounds a sidewall of the source/drain conductive layer and includes a first spacer layer having a first portion and a second spacer layer adjacent the first portion of the first spacer layer. The first portion of the first spacer layer and the second spacer layer are separated by an air gap. The structure further includes a seal layer.