  Using sophisticated string theory calculations, Maldacena and Susskind have
intriguingly shown that near-extremal black holes are characterized by a {\it
finite} mass gap above the corresponding zero-temperature (extremal) black-hole
configuration. In the present compact paper we explicitly prove that the
minimum energy gap ${\cal E}_{\text{gap}}=\hbar^2/M^3$, which characterizes the
mass spectra of near-extremal charged Reissner-Nordstr\"om black holes, can be
inferred from a simple semi-classical analysis.
