Storage device and operating method for applying a program voltage to erased word line to close open memory block

A storage device comprising:

• a nonvolatile memory device comprising an open memory block having at least one erase word line that addresses memory cells existing in an erase state;
• and
• a memory controller configured to transmit a program command to the nonvolatile memory device in response to:
• (1) detecting a powering-on of the storage device and (2) determining that a number of erase word lines, among the at least one erase word line, within the open memory block is not more than a preset value, wherein
• the nonvolatile memory device closes the open memory block by programming a dummy value into each memory cell addressed by the at least one erase word line within the open memory block in a power-on mode in response to the program command.

An operating method executed by a storage device that includes a nonvolatile memory device, the method comprising:

• a) identifying a number of word lines in a memory block of the nonvolatile memory device addressing only memory cells existing in an erase state;
• b) programming, in response to determining that the number is less than a predetermined value, a dummy value into each of the memory cells addressed by the word lines in a power-on mode;
• and
• c) in response to determining that the nonvolatile memory device is not executing a read, program, or erase operation;
• identifying another memory block of the nonvolatile memory de ice having first word lines that address only mentor cells in the erase state and second word lines that address memory cells in a program state differing from the erase state, and
• programming the dummy value into each of the memory cells addressed by the first word lines of the other memory block.