  The Nambu-Jona-Lasinio (NJL) model is one of the most frequently used
four-fermion models in the study of dynamical symmetry breaking. In particular,
the NJL model is convenient for that analysis at finite temperature, chemical
potential and size effects, as has been explored in the last decade. With this
motivation, we investigate the finite-size effects on the phase structure of
the NJL model in $D = 3$ Euclidean dimensions, in the situations that one, two
and three dimensions are compactified. In this context, we employ the
zeta-function and compactification methods to calculate the effective potential
and gap equation. The critical lines that separate trivial and non-trivial
fermion mass phases in a second order transition are obtained. We also analyze
the system at finite temperature, considering the inverse of temperature as the
size of one of the compactified dimensions.
