||The surface properties of the dielectric are important to organic thin film transistors because morphology and the electrical characteristics of organic semiconductor such as pentacene are affected by the dielectric surface. Accordingly, the performance of the pentacene OTFT can be improved by the surface treatment of the dielectric. Herein, the cross-linked buffer layers, poly(hexavinyldisiloxane) (pHVDS) and poly(divinylbezene) (pDVB), are introduced via initiated chemical vapor deposition (iCVD) to modify dielectric surface properties. The iCVD film can be deposited on the dielectric without problems originated from solvents. The pHVDS and the pDVB have relatively flat surface with low surface energy and low chain mobility due to their network structure. As a result, it is confirmed that the cross-linked buffer layers deposited by the iCVD with 5 nm thickness can improve the performance of pentacene TFTs.