Plasma enhanced deposition of amorphous aluminum nitride (AlN) using trimethylaluminum, hydrogen, and nitrogen was performed in a capacitively coupled plasma system. Temp. was varied from 350 to 550 DegC, and pressure dependence of the film structure was investigated. Films were characterized by Fourier transform IR, Rutherford backscattering (RBS), ellipsometry, and x-ray diffraction (XRD). The films are amorphous in nature, as indicated by XRD. Variations in the refractive index were obsd. in ellipsometric measurements, which is explained by the incorporation of carbon in the films, and confirmed by RBS. Capacitance-voltage, conductance-voltage (G-V), and current-voltage measurements were performed to reveal bulk and interface elec. properties. The elec. properties showed marked dependence on processing conditions of the AlN films. Clear peaks as obsd. in the G-V characteristics indicated that the losses are predominantly due to interface states. The interface state d. ranged between 1010 and 1011 eV-1 cm-2. Annealing in hydrogen resulted in lowering of interface state d. values.