Phase structure of lattice QCD with Wilson fermion at finite temperature

We review our attempt at understanding the phase structure of lattice QCD with the Wilson fermion formulation at finite temperature, based on a spontaneous breakdown of parity-flavor symmetry. Numerical results demonstrating explicitly the spontaneous breakdown of parity-flavor symmetry beyond the critical line at both zero and finite temperatures are reported. The phase structure and order of the chiral transition are reported for Nf = 2, 3, and 4 flavors, and the approach towards the continuum limit is discussed. (orig.)