Exponentially increasing global network traffic poses severe challenges to the bandwidth of optical transceivers. Electro-optic modulators (EOMs) with a large bandwidth, low-power consumption, a small footprint, and the possibility of large-scale manufacturing are in demand. In the past few years, tremendous efforts have been made towards a variety of platforms such as silicon (Si)[1,2], germanium-Si (GeSi), indium phosphide (InP), polymers, plasmonics, and thin film lithium niobate (TFLN)[7–12]. Among them, monolithic TFLN EOMs, with etched lithium niobate (LN) waveguides, have attracted more and more attention since they retain excellent material and electro-optic (EO) properties while improving the ability of integration. Several monolithically integrated TFLN Mach–Zehnder modulators (MZMs)[13–16] demonstrated high bandwidth and low half-wave voltage-length product (VπL), which met the requirements for future photonic systems. In those high-performance devices, electron-beam lithography (EBL) with high-exposure resolution served a crucial function of defining high-quality waveguides or electrodes. However, the devices are still on the chip scale, need more exposure time, and are expensive for large-scale manufacturing. For application scenarios like data-center interconnects, EOMs with low cost are necessary. Therefore, photolithography is expected to be applied in the fabrication of monolithic TFLN EOMs due to its high-efficiency exposure on the wafer scale. Previously, photolithography was utilized cooperating with dry etching, but the difficulty of obtaining smooth etching[17,18] via dry etching limited the performance of the manufactured devices. A two-step masking technique and wet etching were proposed to address this problem. Recently, photolithography-exposed EOMs[19–21] were demonstrated on the wafer scale. Although a low VπL was reported, further improvement of bandwidth is also a primary requirement for many applications. Figure 1 shows the comparison of the TFLN EOMs fabricated by EBL and photolithography.