A semiconductor package includes a base having an upper surface and a lower surface opposite to the upper surface. An antenna array structure is embedded at the upper surface of the base. An IC die is mounted on the lower surface of the base in a flip-chip manner so that a backside of the IC die is available for heat dissipation. Solder ball pads are disposed on the lower surface of the base and arranged around the IC die. The semiconductor package further includes a metal thermal interface layer having a backside metal layer that is in direct contact with the backside of the IC die, and a solder paste conformally printed on the backside metal layer.