1. A method for physically unclonable function-identification (PUF-ID) generation, comprising: providing a PUF array having programmable resistance memory cells; performing a forming procedure followed by a programming (ex: SET) procedure on all of the programmable resistance memory cells of the PUF array; performing an estimation process to estimate randomness of the PUF array, by comparing a reference current (I Ref ) of a base unit (ex: MOSFET, without ReRAM) to a total current (I Ttotal ) passing through all of the programmable resistance memory cells for obtaining a PUF randomness; determining a setting result of randomness based on the estimation process; and generating a PUF-ID according to the setting result of randomness.