Patent ID: 8552553

Claim:
A semiconductor device, comprising: a substrate, including: a first surface; at least one substrate pad, the substrate pad being disposed adjacent to the first surface; and a solder mask disposed adjacent to the first surface and partially covering the substrate pad, the solder mask defining at least one solder mask opening so as to expose a part of the substrate pad; a chip, disposed adjacent to the first surface of the substrate and electrically connected to the substrate, the chip including: a chip body, including an active surface; at least one chip pad, disposed adjacent to the active surface; a first passivation, disposed adjacent to the active surface, and defining at least one first passivation opening so as to expose part of the chip pad; and an under ball metal layer, disposed adjacent to the chip pad; at least one metal pillar structure, wherein the metal pillar structure contacts the under ball metal layer to form a first contact surface having a first diameter, the metal pillar structure contacts the exposed part of the substrate pad to form a second contact surface having a second diameter, the first diameter is less than the second diameter, and the second diameter is substantially equal to a diameter of the solder mask opening; and an underfill extending from the first passivation to the solder mask and circumscribing the at least one metal pillar structure.