A package structure includes a first die, a second die over and electrically connected to the first die, an insulating material around the second die, a first antenna extending through the insulating material and electrically connected to the second die, the first antenna being adjacent to a first sidewall of the second die, wherein the first antenna includes a first conductive plate extending through the insulating material, and a plurality of first conductive pillars extending through the insulating material, wherein the first conductive plate is between the plurality of first conductive pillars and the first sidewall of the second die.