High-frequency thin film transistors (TFTs) enable many important thin film circuits used in flexible large-area systems such as large bandwidth instrumentation amplifiers (related to fT) and high-frequency oscillators (related to fmax) [1,2]. In  fmax=10GHz and fT=2.9GHz were reported but using Si substrates and pulsed laser deposition for ZnO growth, which are incompatible with low-cost large-area processing on a meter scale. More modest reports of fmax-=1GHz with sputtered IGZO on glass have relied on a very sensitive alignment process, impractical for fabrication over large substrates . In this work we present a ZnO-channel TFT process fully compatible with flexible large-area substrates. We achieve an fmax=2GHz and fT=860MHz by reducing source/drain (S/D) to gate overlaps (Xov) and scaling channel lengths down to 500nm via a self-aligned process.