  In the present work, we consider the excitonic effects in the twisted bilayer
graphene (tBLG) within the rotated bilayer Hubbard model. Both, intralayer and
interlayer Coulomb interactions have been considered and the half-filling
condition is imposed for the electronic densities is both layers of the
bilayer. We calculate the excitonic pairing gap parameter and the chemical
potential for different twist angles and different values of the interlayer
Coulomb interaction parameter. Furthermore, we show the appearance of the
electronic flat bands in the electronic band structure, mediated by the
excitonic effects. We show that there is a doubling effect of the Dirac's
$K$-point at the low interaction limit and one of Dirac's nodes is stable and
the other one changes its position as a function of rotation angle. At the
large twist angle limit, there appear two additional Dirac-like nodes at the
$M$-point in the Brillouin zone. We show the excitonic red-shift effect of the
principal Dirac's point $K$, in the low interaction limit, while, at the strong
interactions, we get also the blue-shift effect at the $M$-point. Apart from
the mentioned effects, the theory evaluated here predicts a metal-semiconductor
transition in the tBLG system when augmenting the interlayer Coulomb
interaction parameter.
