In an embodiment, a device includes: a first integrated circuit die including a first device layer and a first front-side interconnect structure, the first front-side interconnect structure including first interconnects interconnecting first devices of the first device layer; a second integrated circuit die including a second device layer and a second front-side interconnect structure, the second front-side interconnect structure including second interconnects interconnecting second devices of the second device layer; and an interposer bonded to a back-side of the first integrated circuit die and to a back-side of the second integrated circuit die, the interposer including a die-to-die interconnect structure, the die-to-die interconnect structure including a pillar, the first integrated circuit die overlapping the pillar.