A circuit substrate has the following elements. A stacked circuit structure has a first surface and a second surface opposite thereto surface. A first patterned inner conductive layer is disposed on the first surface and has multiple pads. A first patterned outer conductive layer is disposed on the patterned inner conductive layer and has multiple conductive pillars, wherein each of the first conductive pillar is located on the corresponding first pad. The first dielectric layer covers the first surface, the first patterned inner conductive layer and the first patterned outer conductive layer, and has multiple first concaves, wherein the first concave exposes the top and side of the corresponding first conductive pillar. A semiconductor package structure applied the above circuit substrate and a process for fabricating the same are also provided here.