A rewriteable nonvolatile memory includes a thin film transistor and a
switchable resistor memory element in series. The switchable resistor
element decreases resistance when subjected to a set voltage magnitude
applied in a first direction, and increases resistance when subjected to
a reset voltage magnitude applied in a second direction opposite the
first. The memory cell is formed in an array, such as a monolithic three
dimensional memory array in which multiple memory levels are formed above
a single substrate. The thin film transistor and a switchable resistor
memory element are electrically disposed between a data line and a
reference line which are parallel. A select line extending perpendicular
to the data line and the reference line controls the transistor.