Semiconductor devices including stacked semiconductor chips

A semiconductor device comprising:

• a chip stack structure comprising a first semiconductor chip and a second semiconductor chip stacked on the first semiconductor chip,
• wherein the first semiconductor chip comprises:
• a first substrate;
• a first circuit layer on a front surface of the first substrate;
• and
• a first connecting layer on the first circuit layer, the first connecting layer comprising a first metal pad electrically connected to the first circuit layer,
• wherein the second semiconductor chip comprises:
• a second substrate;
• a second circuit layer on a front surface of the second substrate;
• and
• a second connecting layer on the second circuit layer, the second connecting layer comprising a second metal pad electrically connected to the second circuit layer,
• wherein the first connecting layer and the second connecting layer face each other,
• wherein the first metal pad and the second metal pad are in contact with each other to couple the first and second semiconductor chips to each other,
• wherein the first metal pad comprises a plurality of first metal pad portions separated from each other by first partitions, and
• wherein the second metal pad comprises a plurality of second metal pad portions separated from each other by second partitions.