Semiconductors can conduct when temperature is raised because some electrons will be able to jump the energy gap from the valence shell atomic energy level to the conduction band due to the increase of the kinetic energy of the electrons (with increase in T). Normally, the energy from conduction would require a threshold voltage to overcome the energy band and conduct.
Conductors have no or small energy gaps, so they respond directly to any voltage and allow electrons to move and current to flow.
It is theoretically possible that you could raise the temperature enough on a semiconductor so that it conducts with minimal voltage - I don't think it will ever have a higher conductivity than a metal under the same conditions. BTW, there is a limit to heating leading to more conduction for both metals and semiconductors as interference in the motion of the electrons increase with heating. This is why incandescent light bulbs are not ohmic (linear V-I behavior is ohmic).
