A semiconductor device includes a substrate and a first transistor on a first side of the substrate. The semiconductor device further includes a first electrode contacting a first region of the first transistor. The semiconductor device further includes a spacer extending along a sidewall of the first transistor. The semiconductor device further includes a self-aligned interconnect structure (SIS) separated from at least a portion of the first electrode by the spacer, wherein the SIS extends through the substrate. The semiconductor device further includes a second electrode contacting a surface of the first electrode farthest from the substrate, wherein the second electrode directly contacts the SIS.