Ambipolar field-effect transistor (FET) devices were fabricated with a heterostructure of C-60 and pentacene, and their p- and n-channel field-effect mobilities were studied as a function of thickness of pentacene thin-films. The observed dependences of the mu values were interpreted in terms of the morphology of the thin films and the band structure of C-60/pentacene heterostructure. A complementary metal-oxide-semiconductor (CMOS) circuit was fabricated by integration of two ambipolar FETs, aiming at realization of a new CMOS inverter circuit composed of FETs with the same device structure. The gain of four, the threshold voltage of 85 V, and the complex output characteristics were explained on the basis of the properties of the component FET devices. (c) 2005 Elsevier B.V. All rights reserved.