A package includes a memory stack attached to a logic device, the memory stack including first memory structures, a first redistribution layer over and electrically connected to the first memory structures, second memory structures on the first redistribution layer, a second redistribution layer over and electrically connected to the second memory structures, and first metal pillars on the first redistribution layer and adjacent the second memory structures, the first metal pillars electrically connecting the first redistribution layer and the second redistribution layer, wherein each first memory structure of the first memory structures includes a memory die comprising first contact pads and a peripheral circuitry die comprising second contact pads, wherein the first contact pads of the memory die are bonded to the second contact pads of the peripheral circuitry die.