MEMORY DEVICE

A first chip includes a substrate, and first and second electrodes in a second region surrounding a first region. A second chip includes an interconnect layer, third and fourth electrodes in the second region, and first and second walls. Each of the first and third electrodes and the first wall includes a conductor surrounding the first region. The first and second electrodes are respectively in contact with the third and fourth electrodes. The first and second walls are in contact with the interconnect layer and are electrically coupled to the substrate via the first and third electrodes and the second and fourth electrodes, respectively. Each of a first ratio of an area covered by the first and second electrodes to the second region and a second ratio of an area of the third and fourth electrodes to the second region is 3% or more and 40% or less.