High‐mobility and low‐voltage‐operated organic field‐effect transistors (OFETs) are demonstrated by the design of a new fluorinated benzothiadiazole‐based conjugated polymer with fluorinated high‐k polymer dielectrics. A record‐breaking high hole mobility of 9.0 cm2 V−1 s−1 for benzothiadiazole‐based semiconducting polymers is achieved by the excellent planarity of the semiconducting polymer.