A display device and an apparatus and method for manufacturing the same are disclosed. The display device includes: a substrate; a display unit formed on the substrate; and an inorganic layer formed on the display unit, wherein a water vapor transmission rate (WVTR) of the inorganic layer is 5×10−5 g/m2 day or less. The apparatus for manufacturing a display device includes: a chamber; a shower head for spraying a mixed gas into the chamber; a plasma generation unit for forming plasma from the mixed gas; a susceptor facing the shower head and on which a substrate is seated; and a power supply unit electrically connected to the plasma generation unit, wherein a frequency of a current supplied from the power supply unit to the plasma generation unit is between about 27 MHz and about 42 MHz.