  We introduce the concept of partial and full tunneling processes to explain
the seemingly contradictory non-zero and vanishing tunneling times often
reported in the literature. Our analysis starts by considering the traversal
time of a quantum particle through a potential barrier, including both above
and below-barrier traversals, using the theory of time-of-arrival operators. We
then show that there are three traversal processes corresponding to
non-tunneling, full-tunneling, and partial tunneling. The distinction between
the three depends on the support of the incident wavepackets energy
distribution in relation to the shape of the barrier. Non-tunneling happens
when the energy distribution of the quantum particle lies above the maximum of
the potential barrier. Otherwise, full-tunneling process occurs when the energy
distribution of the particle is below the minimum of the potential barrier. For
this process, the obtained traversal time is interpreted as the tunneling time.
Finally, the partial-tunneling process occurs when the energy distribution lies
between the minimum and maximum of the potential barrier. This signifies that
the quantum particle tunneled only through some portions of the potential
barrier. We argue that the duration for a partial-tunneling process should not
be interpreted as the tunneling time but instead as a partial traversal time to
differentiate it from the full-tunneling process. We then show that a
full-tunneling process is always instantaneous, while a partial-tunneling
process takes a non-zero amount of time. We are then led to the hypothesis that
experimentally measured non-zero and vanishing tunneling times correspond to
partial and full-tunneling processes, respectively.
