Embodiments of the invention include a semiconductor structure containing a back end of line randomly patterned interconnect structure for implementing a physical unclonable function (PUF), a method for forming the semiconductor device, and a circuit for enabling the interconnect structure to implement the physical unclonable function. The method includes forming a semiconductor substrate and a dielectric layer on the substrate. The randomly patterned interconnect structure is formed in the dielectric layer. The random pattern of the interconnect structure is used to implement the physical unclonable function and is a result of defect occurrences during the manufacturing of the semiconductor structure. The circuit includes n-channel and p-channel metal oxide semiconductor field effect transistors (MOSFETs) and the randomly patterned interconnect structure, which acts as electrical connections between the MOSFETs. The random electrical connections between MOSFETs are utilized for generation of unique keys for purposes such as authentication or identification.