Disclosed is a highly reliable physically unclonable function technology. In a tunneling-based memory device disclosed herein, a conductive layer (e.g., Al2O3) is stacked on a bottom electrode, an oxide layer (e.g., TiOx) is stacked on the conductive layer, and a top electrode is stacked on the oxide layer. The tunneling-based memory device has a structure of a memristor crossbar array and has a current-voltage characteristic independent of a temperature that is an external environmental variable due to a tunneling mechanism when constructing an unpredictable physically unclonable function (PUF) of hardware as a memory semiconductor array.