Split rail structures located in adjacent metal layers

A semiconductor device, comprising:

• a first rail structure and a second rail structure that each extends in a first direction in a top view, wherein the first rail structure or the second rail structure includes a power rail or a ground rail of an Integrated Circuit (IC);
• a plurality of first metal lines disposed between the first rail structure and the second rail structure in the top view, wherein the first metal lines each extends in the first direction in the top view;
• a third rail structure and a fourth rail structure that each extends in the first direction in the top view, wherein the third rail structure is located over the first rail structure in a side view, and wherein the fourth rail structure is located over the second rail structure in the side view;
• a plurality of second metal lines disposed between the third rail structure and the fourth rail structure in the top view, wherein the second metal lines each extends in a second direction different from the first direction in the top view, and wherein each of the second metal lines partially overlaps with at least one of the first metal lines in the top view;
• a plurality of first vias that electrically connect the first rail structure to the third rail structure, wherein the first vias are spread out in the top view with respect to the first rail structure or with respect to the third rail structure;
• and
• a plurality of second vias that electrically connect the second rail structure to the fourth rail structure, wherein the second vias are spread out in the top view with respect to the second rail structure or with respect to the fourth rail structure.

A semiconductor device, comprising:

• a first metal layer of a multi-layer interconnect structure, wherein the first metal layer includes:
• a first rail that extends in a first direction in a top view;
• a second rail that extends in the first direction in the top view;
• and
• a plurality of first metal lines disposed between the first rail and the second rail in the top view, wherein the first metal lines each extends in the first direction in the top view;
• a second metal layer of the multi-layer interconnect structure, wherein the second metal layer is located one level above the first metal layer and includes:
• a third rail that extends in the first direction in the top view;
• a fourth rail that extends in the first direction in the top view;
• a plurality of second metal lines disposed between the third rail and the fourth rail in the top view, wherein the second metal lines each extends in a second direction in the top view, the second direction being perpendicular to the first direction;
• at least three first vias that are disposed directly above the first rail and directly below the third rail in a side view;
• and
• at least three second vias that are disposed directly above the second rail and directly below the fourth rail in the side view.