A set of physical unclonable function (PUF) cells is configured with a set of capacitive devices in an integrated circuit (IC). A subset of PUF cells includes a corresponding subset of capacitive devices that have failed during fabrication. A charging current sufficient to charge an operational capacitive device in a PUF cell is sent to the set of PUF cells. A determination is made whether an output voltage of a PUF cell exceeds a threshold. When the output voltage exceeding the threshold, a logic value of 1 is produced at a position in a bit-string. The determination and the producing is repeated for each PUF cell in the set to output a bit-string, which includes 1s and 0s in random positions. The bit-string is used in a security application as a random stable value owing to a random pattern of 1s and 0s present in the bit-string.