Al/Poly(methyl methacrylate)(PMMA)/p-Si organic Schottky devices were fabricated on a p-Si semiconductor wafer by spin coating of PMMA solution. The frequency and voltage dependent dielectric constant of Al/PMMA/p-Si have been investigated. Dielectric properties and electrical conductivity of Al/PMMA/p-Si structure have been investigated in detail by using experimental C-V and G-V measurements in the frequency range of 30 kHz-1 MHz and voltage from -4 V to 4 V. The frequency and voltage dependent dielectric constant epsilon', dielectric loss epsilon '', tangent loss (tan delta), electrical modulus (M' and M ''), and ac electrical conductivity sigma(AC) Properties of Al/PMMA/p-Si structure have been investigated in the various frequencies at room temperature. It can be concluded that the interfacial polarization can be more easily occurred at low frequencies, and the majority of interface states at metal-semiconductor interface, contributes to deviation of dielectric properties of Al/(PMMA)/p-Si structures. (C) 2015 Elsevier Ltd. All rights reserved.