Bonded three-dimensional memory devices and methods for forming the same

A method for forming a three-dimensional (3D) memory device, comprising:

• forming, on a first substrate, a plurality of first NAND memory strings, a plurality of first bit lines (BLs) conductively connected to the first NAND memory strings, a plurality of first conductor layers, and a first bonding layer comprising a plurality of first bit line bonding contacts conductively connected to the first BLs, and a plurality of first word line bonding contacts conductively connected to the first conductor layers, to form a first semiconductor structure;
• forming, on a second substrate, a plurality of second NAND memory strings, a plurality of second BLs conductively connected to the second NAND memory strings, a plurality of second conductor layers, and a second bonding layer comprising a plurality of second bit line bonding contacts conductively connected to the second BLs, and a plurality of second word line bonding contacts conductively connected to the second conductor layers, to form a second semiconductor structure;
• and
• bonding the first semiconductor structure and the second semiconductor structure in a face-to-face manner, such that (i) the first semiconductor structure is bonded to the second semiconductor structure, (ii) the first BLs are respectively conductively connected to the second BLs through the bonded first and the second bit line bonding contacts at a bonding interface, and (iii) the first conductor layers are conductively connected to the second conductor layers through the bonded first and second bit line bonding contacts at the bonding interface.