Semiconductor memory device and method for refreshing memory cells

摘要

A semiconductor memory device is provided. The semiconductor memory device includes a memory block including a plurality of memory cells; a default refresh controller configured to receive a refresh command from a host, to generate a default refresh signal, and to control the memory cells to be refreshed; and a weak cell refresh controller configured to receive the default refresh signal, to generate a weak cell refresh signal, and to control a weak cell among the memory cells to be refreshed. The weak cell may be refreshed at least one more time during a refresh period during which all of the memory cells are refreshed by the default refresh controller. The semiconductor memory device performs at least one more refresh on a weak cell having a data retention time shorter than a refresh period apart from a normal default refresh, thereby preventing data loss.

主权项

1. A semiconductor memory device comprising:
a memory block comprising a plurality of volatile memory cells; a default refresh controller responsive to a series of refresh commands received externally with respect to the semiconductor memory device, each of the refresh commands targeting a corresponding memory cell group of the volatile memory cells of the memory block to be refreshed, the default refresh controller configured, in response to each of the received refresh commands, to control at least one default refresh operation corresponding to each of the refresh commands for the respective memory cell group targeted by the corresponding refresh command; and a weak cell refresh controller configured to control at least one refresh operation of weak cell memory groups including a first memory cell group, the weak cell refresh controller responsive to a received refresh command that targets a memory cell group different from the first memory cell group and does not target the first memory cell group to control at least one refresh operation of the first memory cell group.