Microelectronic device package including antenna horn and semiconductor device

A microelectronic device package, comprising:

• a multilayer package substrate comprising conductor layers spaced from one another by dielectric material, and comprising vertical connections extending through the dielectric material between the conductor layers and coupling portions of the conductor layers one to another, the multilayer package substrate having a device side surface and an opposite board side surface;
• an antenna formed in a first conductor layer at or below the device side surface of the multilayer package substrate;
• a reflector formed in a second conductor layer of the multilayer package substrate, the reflector aligned with and spaced away from the antenna by the dielectric material toward the board side surface;
• a ground plane formed at the device side surface of the multilayer package substrate;
• an antenna horn mounting structure formed on the ground plane and extending above the device side surface;
• an antenna horn positioned on the mounting structure and aligned with the antenna;
• and
• a semiconductor die mounted to the device side surface of the multilayer package substrate and coupled to the antenna.