Tunnel junctions with AI-N barriers fabricated by microwave-excited plasma were studied. When the Al thickness, nitridation time, and annealing temperature were 1 nm (0.8 nm), 50 s (35 s), and 280 ? C ( 300 ? C ), TMR ratio and resistance-area product (RA) were 49% (34%) and 3 {\times}10 4 Ω μ\m 2 ( 1.5 {\times}10 4 Ω μ\m 2 ), respectively. In order to clarify the annealing temperature dependence of TMR ratio, the local transport properties were measured for Ta 5 nm/Cu 20 nm/Ta 5 nm 29 76 Fe 24 2 nm/Cu 5 nm/M n 75 Ir 25 10 nm/ Co 71 Co 29 4nm/Al-N junction with Al thickness of 0.8 nm and nitridation time of 35s at various temperatures. The increase of TMR ratio after annealing at 300 ? C , where the TMR ratio of the corresponding MTJ had the maximum value of 34%, can be well explained by the enhancement of the average barrier height ( Φ ave ) and the reduction of its fluctuation. After further annealing at 340 ? C , the leakage current was observed and the TMR ratio decreaseded