ultrathin nitrided oxides (7.7 nm) were reoxidized for the first time by lamp-heated rapid thermal annealing in o/sub 2/ at 900-1150 degrees c for 15-600 s. compositions and residual hydrogen contents in various reoxidized nitrided oxides were studied by auger electron spectroscopy (aes) and secondary ion mass spectroscopy (sims), respectively. aes analyses show that as reoxidation proceeds, the nitrogen concentration peak near the outer surface decreases rapidly, while that near the si-sio/sub 2/ interface (n)/sub int/ decreases very slowly. it is newly found that the nitrogen-rich layer near the si-sio/sub 2/ interface moves further into the substrate as reoxidation proceeds, following a movement similar to that of the si-sio/sub 2/ interface. as the starting nitrogen content is lowered or the reoxidation temperature is raised, the distance of the peak movement delta d/sub aes/ and the reduction of (n)/sub int/ are larger. the delta d/sub aes/ is found in quantitatively good agreement with the increase of film thickness evaluated by capacitance-voltage measurements. the movements are due to the diffusion-limited interfacial oxidation. in contrast to reoxidation, annealing in n/sub 2/ of nitrided oxides scarcely reduces the (n)/sub int/ and does not increase delta d/sub aes/ sims analyses show that as reoxidation proceeds, hydrogen concentration (h) in the film decreases monotonically. as the starting nitrogen content is lowered or the reoxidation temperature is raised, (h) decreases more rapidly. electron trapping was monitored by flat-band voltage shift delta v/sub fb/ u