Packaged semiconductor device and method of forming thereof

A semiconductor device comprising:

• a first die, the first die comprising:
• a first substrate;
• a first plurality of bonding pads over the first substrate, the first plurality of bonding pads having a first pitch;
• a second die attached to the first die, the second die comprising:
• a second substrate;
• a first interconnect structure over an active side of the second substrate;
• a second interconnect structure over a backside of the second substrate;
• a power distribution network (PDN) structure over the second interconnect structure such that the second interconnect structure is interposed between the PDN structure and the second substrate;
• a second plurality of bonding pads over the PDN structure, the second plurality of bonding pads bonded to the first plurality of bonding pads;
• and
• a third plurality of bonding pads over the first interconnect structure, the third plurality of bonding pads having a second pitch, the second pitch being less than the first pitch;
• and
• a third die attached to the second die, wherein the second die is between the first die and the third die, the third die comprising:
• a third substrate;
• and
• a fourth plurality of bonding pads over an active side of the third substrate, the fourth plurality of bonding pads bonded to the third plurality of bonding pads.

A method of forming a semiconductor device, the method comprising:

• forming a first bonding layer and a first plurality of bonding pads over a first wafer;
• forming a second bonding layer and a second plurality of bonding pads over a first surface of a second wafer;
• bonding the first wafer to the second wafer, the bonding comprising bonding the first bonding layer to the second bonding layer and bonding each bonding pad of the first plurality of bonding pads with a respective bonding pad of the second plurality of bonding pads;
• forming a power distribution network (PDN) layer over a second surface of the second wafer, the second surface being opposite the first surface;
• forming a third bonding layer and a third plurality of bonding pads over the PDN layer;
• forming a fourth bonding layer and a fourth plurality of bonding pads over a third wafer;
• and
• bonding the second wafer to the third wafer, the bonding comprising bonding the third bonding layer to the fourth bonding layer and bonding each bonding pad of the third plurality of bonding pads with a respective bonding pad of the fourth plurality of bonding pads.