An access method of a nonvolatile memory device included in a user device includes receiving a write request to write data into the nonvolatile memory device; detecting an application issuing the write request, a user context, a queue size of a write buffer, an attribute of the write-requested data, or an operation mode of the user device; and deciding one of a plurality of write modes to use for writing the write-requested data into the nonvolatile memory device according to the detected information. The write modes have different program voltages and verify voltage sets.