  Dynamical symmetry breaking in three-dimensional QED with N fermion flavours
is considered at finite temperature, in the large $N$ approximation. Using an
approximate treatment of the Schwinger-Dyson equation for the fermion
self-energy, we find that chiral symmetry is restored above a certain critical
temperature which depends itself on $N$. We find that the ratio of the
zero-momentum zero-temperature fermion mass to the critical temperature has a
large value compared with four-fermion theories, as had been suggested in a
previous work with a momentum-independent self-energy. Evidence of a
temperature- dependent critical $N$ is shown to appear in this approximation.
The phase diagram for spontaneous mass generation in the theory is presented in
$T-N$ space.
