In this work, we demonstrated a poly(4-vinylphenol-co-methyl methacrylate) (PVP-co-PMMA)/Al2O3 double-stacked insulator deposited by solution process. The double-stacked insulator exhibited higher degree of performance uniformity than individual single-stacked insulators. We fabricated an inverter circuit in order to demonstrate the applicability of the proposed insulator in complementary logic circuits, which are composed of metal oxide thin film transistors as the n-channel device and organic thin film transistors as the p-channel device. We utilized amorphous indium gallium zinc oxide thin film transistor and pentacene thin film transistor for the n-channel and p-channel devices, respectively. It was observed that the PVP-co-PMMA/Al2O3 double-stacked insulator had the effect of overcoming the problems related to individual single-stacked layers, such as high leakage current of Al2O3 and low dielectric constant of PVP-co-PMMA. The inverter operated at a threshold voltage of 1.5 V and exhibited high voltage gain of 17.3 V/V at the supply voltage of 3 V.