  We investigate the doping-driven metal-insulator transition of the
(2+1)-dimensional Hubbard model in the path-integral formalism with the tensor
renormalization group method. We calculate the electron density $\langle
n\rangle$ as a function of the chemical potential $\mu$ choosing three values
of the Coulomb potential with $U=80$, $8$, and $2$ as representative cases of
the strong, intermediate, and weak couplings. We have determined the critical
chemical potential at each $U$, where the Hubbard model undergoes the
metal-insulator transition from the half-filling plateau with $\langle
n\rangle=1$ to the metallic state with $\langle n\rangle > 1$. Our results
indicate that the model exhibits the metal-insulator transition over the vast
region of the finite coupling $U$.
