Disclosed are semiconductor packages and their fabrication methods. The semiconductor package comprises a first structure that includes a conductive pattern, a second structure spaced apart from the first structure, a pillar structure between the first structure and the second structure and electrically connecting the first structure to the second structure, and a semiconductor chip between the first structure and the second structure. The pillar structure includes an inner pillar on the conductive pattern and an outer pillar that surrounds the inner pillar. The outer pillar is in contact with a sidewall and a top surface of the inner pillar.