Underfill material flow control for reduced die-to-die spacing in semiconductor packages and the resulting semiconductor packages are described. In an example, a semiconductor apparatus includes first and second semiconductor dies, each having a surface with an integrated circuit thereon coupled to contact pads of an uppermost metallization layer of a common semiconductor package substrate by a plurality of conductive contacts, the first and second semiconductor dies separated by a spacing. A barrier structure is disposed between the first semiconductor die and the common semiconductor package substrate and at least partially underneath the first semiconductor die. An underfill material layer is in contact with the second semiconductor die and with the barrier structure, but not in contact with the first semiconductor die.