A semiconductor wiring substrate includes a first circuit layer, a second circuit layer and a first dielectric layer. The first circuit layer includes a plurality of first signal traces and a plurality of first ground traces, wherein the first signal traces and the first ground traces are alternatively arranged on the first circuit layer, and one of the first signal traces is spaced at a first spacing from adjacent one of the first ground traces. The first dielectric layer is between the first circuit layer and the second circuit layer and has a first thickness in an arrangement direction of the first circuit layer, the first dielectric layer and the second circuit layer, wherein the first spacing substantially ranges from 0.78 to 1.96 times the first thickness.