A process for forming a circuit structure includes providing a first composite-layer structure at first. A second composite-layer structure is then provided. The first composite-layer structure, a second dielectric layer and the second composite-layer structure are pressed so that a second circuit pattern and an independent via pad are embedded in the second dielectric layer, and the second dielectric layer is connected to the first dielectric layer. A first carrier substrate and a second carrier substrate are removed to expose a first circuit pattern and the second circuit pattern. At least one first opening that passes through the second dielectric layer and exposes the independent via pad is formed, and the first opening is filled with a conductive material to form a second conductive via that connects the independent via pad and a second via pad.