ZnS:Mn TFEL devices were fabricated by electron-beam evaporation method and then the electro-optical properties were investigated. To investigate the capacitance which was due to oxygen vacancy at the Ta 2 O 5 thin film, AES(Auger Electron Spectroscopy) and C-F(capacitance-frequency) measurements were used. It was found that the capacitance was decreased by annealing the Ta 2 O 5 film in oxygen ambience. From EL emission measurement, we observed the EL emission spectrum which had the peak range from 550nm and 650nm. This emission is associated with the transition from 4 T 1 ( 4 G) first excited state to 6 A 1 ( 6 S) ground state in the 3d 5 energy level configuration of Mn 2+ occurs. The threshold voltage of EL device with Ta 2 O 5 insulator layer was found to be 24V~28V. The CIE color coordinates of these emission are X=0.5151, Y=0.4202 which is yellowish orange emitting. The EL device using Ta 2 O 5 insulator layer can be driven with a low voltage which is beneficial to the practical application.