Each of a first and a second integrated circuit structures has hole(s) in the top surface, and capacitors at least partially located in the holes. A semiconductor die is attached to the top surface of the second structure. Then the first and second structures are bonded together so that the die becomes disposed in the first structure's cavity, and the holes of the two structures are aligned to electrically connect the respective capacitors to each other. A filler is injected into the cavity through one or more channels in the substrate of the first structure. Other embodiments are also provided.