Experimental results are presented for gate oxide degradation under direct tunneling stress conditions using p- and n-MOSFET's with gate oxides that are treated with high-pressure hydrogen and deuterium annealing. Device parameter variations as well as the gate leakage current depend on and are improved by high-pressure deuterium annealing, compared to corresponding hydrogen annealing. The precursor for oxide trap is probably created in the bulk of the gate oxide, which depends on hydrogen concentration levels, however its generation is not related with SiO2/Si interface reaction that produces the released hydrogen. The treatment with deuterium instead of hydrogen in device fabrication provides a possible solution to reduce the generation of oxide-trap precursor within the gate oxide. (c) 2005 Elsevier Ltd. All rights reserved.