In this research, the effect of Ar/N₂-plasma sputtering gas pressure on the LaB_xN_y tunnel and block layer was investigated for pentacene-based floating-gate memory with an amorphous rubrene (α-rubrene) passivation layer. The influence of α-rubrene passivation layer for memory characteristic was examined. The pentacene-based metal/insulator/metal/insulator/semiconductor (MIMIS) diode and organic field-effect transistor (OFET) were fabricated utilizing N-doped LaB₆ metal layer and LaB_xN_y insulator with α-rubrene passivation layer at annealing temperature of 200^°C. In the case of MIMIS diode, the leakage current density and the equivalent oxide thickness (EOT) were decreased from 1.2×10^-2 A/cm² to 1.1×10^-7 A/cm² and 3.5 nm to 3.1 nm, respectively, by decreasing the sputtering gas pressure from 0.47 Pa to 0.19 Pa. In the case of floating-gate type OFET with α-rubrene passivation layer, the larger memory window of 0.68 V was obtained with saturation mobility of 2.2×10^-2 cm²/(V·s) and subthreshold swing of 199 mV/dec compared to the device without α-rubrene passivation layer.