Semiconductor device

A semiconductor package comprising:

• a first sub-package including a first semiconductor chip;
• a second sub-package disposed on the first sub-package and including a second semiconductor chip;
• and
• an inter-package connection structure connecting the first sub-package to the second sub-package,
• wherein each of the first sub-package and the second sub-package comprises
• a lower redistribution layer structure,
• a bump pad disposed under the lower redistribution layer structure, the bump pad having an upper structure of a first width and a lower structure of a second width less than the first width,
• a metal seed layer disposed along a lower surface of the upper structure and a side surface of the lower structure,
• a lower insulating layer surrounding the lower redistribution layer structure and the bump pad, and
• a bump structure disposed under the bump pad,
• wherein a first undercut is disposed at one end of the metal seed layer that contacts the upper structure and a second undercut is disposed at an other end of the metal seed layer that contacts the lower structure.

A semiconductor package comprising:

• a bump structure;
• a T-shaped bump pad disposed on the bump structure, the T-shaped bump pad having an upper structure and a lower structure with a step difference between the upper structure and the lower structure;
• a redistribution layer structure disposed on the T-shaped bump pad and having a plurality of redistribution layer lines;
• a plurality of insulating layers surrounding the redistribution layer structure and the T-shaped bump pad;
• a metal seed layer conformally disposed between a lower surface of the upper structure and a lowermost insulating layer of the plurality of insulating layers, and between a side surface of the lower structure and the lowermost insulating layer;
• and
• a semiconductor chip disposed on the redistribution layer structure and electrically connected to the bump structure,
• wherein a first undercut is disposed at one end of the metal seed layer, a second undercut is disposed at an other end of the metal seed layer, and the first undercut and the second undercut extend orthogonal to each other.