Dielectric characterization of metal-interlayer-semiconductor (MIS) structures of N-doped Diamond-Like Carbon (N:DLC) film-coated interlayer is performed to assess their dielectric properties, AC electrical conductivity (sigma(ac)), and polarization mechanisms. The interlayer's structural analysis is performed using Scanning Electron Microscopy (SEM) and X-ray Photo-electron Spectroscopy (XPS). The in-phase and out-of-phase parts of the complex dielectric constant (epsilon & lowast;), the complex electric modulus (M & lowast;), the values of tangent loss (tan delta), and sigma(ac) are determined utilizing admittance-voltage (Y = 1/Z = G + j omega C) measurements revealing that their strong sensitivity to voltage and frequency. Remarkably, a relative permittivity (epsilon ') of 407 at 1 kHz, 104 times higher than traditional SiO2 insulators, is observed, suggesting a significantly enhanced electron density and energy storage capacity for ultracapacitors. The double logarithmic sigma(ac) vs f plot slope changes between 0.36 and 0.20 at strong accumulation. The intersection point in sigma(ac) implies a lack of free electrons at higher frequencies, suggesting an electron trapping or recombination process.