Ambipolar transistors typically suffer from large off-current inherently due to ambipolar conduction. Using a tri-gate transistor it is shown that it is possible to electrostatically switch ambipolar polymer transistors from ambipolar to unipolar mode. In unipolar mode, symmetric characteristics with an on/off current ratio of larger than 105 are obtained. This enables easy integration into low-power complementary logic and volatile electronic memories. cop. 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.