  A model of 2D massive Dirac fermions, interacting with a instantaneous $1/r$
Coulomb interaction, is presented to mimic the physics of gapped graphene. The
static polarization function is calculated explicitly to analyze screening
effect at the finite temperature and density. Results are compared with the
massless case . We also show that various other works can be reproduced within
our model in a straightforward and unified manner.
