In this paper, electrical and reliability properties of N$_2$O oxides, grown at the temperature of 95$0^{circ}C$ and 100$0^{circ}C$ to 74$AA$, and 82$AA$. respectively, using NS12TO gas in a conventional furnace, have been compared with those of pure oxide grown at the temperature of 850 to 84$AA$ using O$_2$ gas. Initial IS1gT-VS1gT characteristics of N$_2$O oxides were similar to those of pure oxide, and reliability properties of N$_2$O oxides, such as charge trapping, interface state density and leakage current at low electric field under F-N stress, were improved much better than those of pure oxide. But, with increasing capacitor area. TDDB characteristics of N$_2$O oxides were more degraded than those of pure oxide and this degradation of TDDB characteristics was more severe in 100$0^{circ}C$ N$_2$Ooxide than in 95$0^{circ}C$ N$_2$O oxide. The improvement of reliability properties excluding TDDB in N$_2$Ooxides was attributed to the hardness of the interface improved by nitrogen pile-up at the interface of Si/SiO$_2$, but on the other hand, the degradation of TDDB characteristics in N$_2$O oxides was obsered due to the increase of local thinning spots caused by excessive nitrogen at interface during the growth of N$_2$O oxides.