H and D surface nanochemistry on an advanced wide band gap semiconductor, silicon carbide is investigated by synchrotron radiation-based core level and valence band photoemission, infrared absorption and scanning tunneling spectroscopy, showing the 1st example of H/D-induced semiconductor surface metallization, that also occurs on a pre-oxidized surface. These results are compared to recent state-of-the-art ab-initio total energy calculations. Most interestingly, an amazing isotopic behavior is observed with a smaller charge transfer from D atoms suggesting the role of dynamical effects. Such findings are especially exciting in semiconductor physics and in interface with biology.