A wiring board (20A) includes a first wiring portion (10A) having a plurality of wiring layers (1) and external connecting bumps (5), and at least one second wiring portion (15A) having a plurality of contact plugs (14). The second wiring portion is integrated with the first wiring portion such that each terminal (14a) of the second wiring portion is in direct contact with one of the wiring layers of the first wiring portion. Hence, there is no risk to produce an internal stress caused by the diffused component of the solder bump in the junction portion between the second and first wiring portions. Accordingly, even when a semiconductor chip (30) of a low-k material is highly integrated on the wiring board, a highly reliable semiconductor device (50) can be obtained.