The semiconductor device (11) of the invention comprises a circuit that is
covered by a passivation structure. It is provided with a first security
element (12) that comprises a local area of the passivation structure and
which has a first impedance. Preferably, a plurality of security elements
(12) is present, whose the impedances differ. The semiconductor device
(11) further comprises measuring means (4) for measuring an actual value
of the first impedance, and a memory (7) comprising a first memory
element (7A) for storing the actual value as a first reference value in
the first memory element (7A). The semiconductor device (11) of the
invention can be initialized by a method wherein the actual value is
stored as the first reference value. Its authenticity can be checked by
comparison of the actual value again measured and the first reference
value.