A circuit board is disposed on a substrate and includes a dielectric layer and a circuit layer. The dielectric layer is disposed on the substrate. The circuit layer is embedded in the dielectric layer and has plural traces. Each of the traces has a first top surface and a first bottom surface which are opposite to each other, and the first bottom surface faces toward the substrate. The first top surface is exposed from the dielectric layer, and an area of a vertical projection of the first top surface on the substrate is smaller than an area of a vertical projection of the first bottom surface on the substrate.