Polymer field-effect transistors (PFETs) are promising candidates for future electronics due to easy and inexpensive fabrication. Poly{[N, N'-bis(2-octyldodecyl)-naphthalene-1,4,5,8-bis(dicarboximide)-2,6-diyl]- alt-5,5'-(2,2'-bithiophene) [P(NDI2OD-T2)] based PFET devices with poly (methyl 2-methylpropenoate) (PMMA) as dielectric were fabricated successfully and it was found that the charge transporting behaviors were greatly impacted by the molecular weight of PMMA. Both hole and electron mobilities were improved simultaneously with increasing molecular weight of PMMA. In addition, similar result was also obtained in the PFETs based on a semiconductor, poly{[N, N'-bis(2-octyldodecyl)-1,4,5,8- naphthalenediimide-2,6-diyl-alt- 5,5'-di(thiophen-2-yl)-2,2'-(E)-2-(2-(thiophen-2-yl) vinyl) thiophene]}. Furthermore, the corresponding complementary-like inverters with PMMA displayed a gain value of 100. We studied the interface between the semiconducting and dielectric layers and found that the low trap density with higher-molecular-weight PMMA attributes to high mobilities of electrons and holes. This work provides a new way to fabricate high-performance PFETs and to improve performance of the complementary circuits through studying the effects of polymeric gate dielectrics, compared to the conventional view of semiconducting materials. (C) 2016 Elsevier Ltd. All rights reserved.