Recently, organic electronics has become an object of research in field of electronic devices because organic semiconductor materials have many advantages such as flexibility, low-cost production and low-temperature process. The purpose of this research is to fabricate metal-oxide-semiconductor (MOS) diodes and transistors using organic semiconductor materials called pentacene which is commonly used p-type organic semiconductor to fabricate organic devices such as MOS diodes and transistors because of its availability and stability. The lowest minimum capacitance in depletion region and the highest maximum capacitance in accumulation region obtained in this research were 0.1μF/cm2 at 5 V and 0.9μF/cm2 at -5 V, respectively. The highest magnitude of drain current measured in this research was around 1.4 μA at drain and gate voltage of -5 V.