Semiconductor memory devices and methods of manufacturing thereof

A method, comprising:

• forming a first memory array comprising a plurality of first conductive structures extending along a vertical direction, each of the first conductive structures electrically coupled to a plurality of first memory cells;
• forming a plurality of second conductive structures over the first memory array, each of the plurality of second conductive structures having a bowl shape;
• and
• forming, over the second conductive structures, a second memory array comprising a plurality of third conductive structures along the vertical direction, each of the third conductive structures electrically coupled to a plurality of second memory cells;
• wherein the bowl shape of each of the second conductive structures has an exterior bottom surface in contact with a corresponding one of the plurality of first conductive structures and an interior bottom surface in contact with a corresponding one of the plurality of third conductive structures.

A method, comprising:

• forming a first memory array comprising a plurality of first source lines and a plurality of first bit lines extending along a vertical direction;
• forming a plurality of bowl-shaped conductive structure over the first memory array;
• and
• forming, over the plurality of bowl-shaped conductive structures, a second memory array comprising a plurality of second source lines and a plurality of second bit lines extending along the vertical direction;
• wherein the plurality of bowl-shaped conductive structures each have an exterior bottom surface in contact with a corresponding one of the plurality of first source lines or bit lines, and an interior bottom surface in contact with a corresponding one of the plurality of second source lines or bit lines.