Physical unclonable function

A semiconductor chip comprising:

• a substrate having a major surface;
• a physical unclonable function (PUF) region of the substrate that includes a plurality of devices, connected to one another in an M×N array, with read logic that measures drive current of the plurality of devices to generate a security code, and having a first work function metal (WFM) with random variations around a first thickness formed on a channel fin between the channel fin and a gate cut passing (CT) fin, such that a first subset of the plurality of devices has a WFM thickness below the first thickness and a second subset of the plurality of devices has a WFM thickness above the first thickness, with a PUF being defined in accordance with a random distribution of the first subset and the second subset;
• and
• an operational region that includes a plurality of operational FETs on the major surface, wherein all of the operational FETs have a second WFM with a greater thickness than the first thickness.