Semiconductor package and a method of fabricating the same

A semiconductor package, comprising:

• a lower package that includes a lower package sUbstrate, a lower semiconductor chip on the lower package substrate, and a lower molding part that is on the lower package substrate and covers the lower semiconductor chip;
• an upper package on the lower package, the upper package including an upper package substrate, first and second upper semiconductor chips on the upper package substrate, and an upper molding part that is on the upper package substrate and covers the upper semiconductor chips;
• an interposer substrate between the upper package substrate and the lower semiconductor chip;
• and
• an under-fill part that fills a space between the interposer substrate and the upper package substrate,
• wherein the under-fill part includes a protrusion extended between the upper package substrate and the upper molding part toward a top surface of the upper molding part, and
• wherein the upper molding part includes a first segment disposed between the upper package substrate and the protrusion.