This study examined the effects of NH3-Plasma treatment on the gate insulator (SiO2) surface before pentacene deposition. The NH3-plasma treatment can improve the interface property between SiO2/pentacene, providing a suitable surface for pentacene growth. Moreover, the NH3-plasma treatment can also help terminate dangling bonds at the SiO2 surface and thus reduce the interface trap-state density. The proposed method provides a simple and effective method for treating the interface between SiO2/pentacene, reducing interface traps and simultaneously improving pentacene crystallization. Crown Copyright @ 2008 Published by Elsevier Ltd. All rights reserved.