The importance, development, and implementation of high-k gate dielectrics for modern organic electronics applications have been reported. Insulators or dielectric materials are characterized by the absence of charge transport. Dielectrics are widely used in numerous applications. The most fundamental of these is their use as an insulating layer against electrical conduction. There are specific requirements for gate dielectrics to be used in field-effect transistors. The presence of grain boundaries in thin semiconducting films cannot be neglected, because they can have a significant influence on the measured mobility as well as on the subthreshold slope, and it is related to grain size. The low leakage nanodielectrics have allowed the fabrication of very thin gate dielectrics, which translate into higher capacitances, and enhance the performance of both organic and inorganic FETs. The use of stacked inorganic-organic layers offers a good option because it overcomes the drawback of the poor compatibility of most metal oxides with organic semiconductors and usually reduces the roughness of the dielectric layer.