  The temperature dependence of d-wave superconducting order for two
dimensional fermions with d-wave attraction is investigated by means of the
functional renormalization group with partial bosonization. Below the critical
temperature T_c we find superconductivity, a gap in the electron propagator and
a temperature dependent anomalous dimension. At T_c the renormalized
"superfluid density" jumps and the approach to T_c from above is characterized
by essential scaling. These features are characteristic for a phase transition
of the Kosterlitz-Thouless (KT) type.
