US Patent 10224080 Semiconductor memory device with late write feature

A stack memory includes a base chip, a memory chip stacked over the base chip, and a via 42 provided between the base chip and the memory chip. The base chip has an external interface circuit and a late write control circuit. The external interface circuit externally receives/transmits write data and read data. The late write control circuit has at least a register storing write data externally supplied through the external interface circuit. The memory chip has a memory cell array and a late write control circuit having at least a register storing write data supplied from the register through the via.