In this paper we will show the advantages of employing transparent free-standing dielectric films to realize OFETs devices with optimized performances. These advantages concern several aspects, ranging from optimized device performances, to extended versatility in applications. Organic field effect transistors made from a Polyethilene Terephtalate film (Mylar) as a dielectric are presented: these devices are particularly interesting especially in sight of possible applications as chemical and mechanical sensors. In addition, we will show preliminary results obtained from films of Poly Dimethyl Siloxane (PDMS), a polymer whose surface is hydroxyl-free. This feature should allow to obtain ambipolar transport properties in OFETs. Preliminary results on MIS structures are presented. (C) 2007 Elsevier B.V. All rights reserved.