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Jeon et al. Soft Sci. 2025, 5, 1 https://dx.doi.org/10.20517/ss.2024.35 Page 3 of 39

Currently, along with the advancement of next-generation soft electronics, the development of MO TFT
technology is accelerating to meet demands beyond flexible and transparent displays. This includes
achieving higher resolution, lower power consumption, and accommodating new functionalities and form
factors, marking a significant shift toward innovative applications such as foldable and wearable devices,
automotive displays, and smart sensors [8,10,12,22,23] . MO TFTs play a key role not only in the advancement of
displays, but also in the expansion into various flexible and stretchable electronic components for soft
electronics. This includes applications such as efficient memory systems, flexible and stretchable circuits,
sensors and advanced processors [24-34] . MO TFTs also highlight the transformative potential of next-
generation Internet of Things (IoT) devices and advanced technologies such as artificial intelligence (AI)
and neuromorphic computing [35-42] . In the rapidly evolving landscape of augmented reality (AR) and virtual
reality (VR), the demand for high-performance display technologies continues to grow. MO TFTs have
emerged as key components due to their exceptional transparency and low power consumption, making
them indispensable for the realization of high-resolution backplane applications in AR/VR devices [43,44] .
These TFTs not only enhance visual clarity, but also enable immersive user experiences by driving advances
in display quality and efficiency. Furthermore, MO TFTs are increasingly valued for their unique
capabilities in back-end-of-line (BEOL) processing and monolithic 3D (M3D) integration [45-48] . Their low
processing temperatures, superior stability and low leakage characteristics allow seamless integration with
existing silicon CMOS chips in BEOL processes, enabling higher transistor densities and more compact
layouts. This compatibility not only improves the performance and efficiency of integrated circuits, but also
opens new avenues for the development of advanced M3D architectures that promise significant advances
in semiconductor technology.

Despite their critical role in advancing soft electronics, flexible MO TFTs face significant challenges due to
inherent characteristics such as brittleness and limited electrical performance at low process temperatures.
Balancing high electrical performance, reliability, and flexibility remains a complex task, particularly
ensuring that these devices withstand mechanical stress and maintain functionality over extended bending
cycles and varying bending radii. Furthermore, research is advancing beyond flexibility towards the
development of stretchable MO TFTs, seen as key enablers for future applications such as wearable health
monitors, electronic skin (e-skin), neuromorphic devices, and advanced human-machine interfaces [49-51] .
This development focuses on novel materials and device architectures that maintain performance under
large strains, often employing stretchable substrates combined with MO or organic semiconductors for
electronic and mechanical robustness. Additionally, stretchable TFTs incorporate innovative geometries,
such as serpentine or mesh structures, allowing deformation without sacrificing electrical properties, thus
enhancing their potential in soft, stretchable electronics [51-54] . As a result, recent studies have focused
extensively on improving the performance, processes, and structural design of flexible and stretchable MO
TFT devices to increase mechanical stress resistance while minimizing electrical performance degradation
and variability.

In this review, we investigate the substrate, materials, fabrication processes, device structures, and
applications of high-performance flexible MO TFTs as shown in Figure 1. Firstly, in the substrate section,
we classify the types of substrates for employing high-performance flexible MO TFTs into polymer, paper,
and metal foil, and then describe the characteristics and types of each. Secondly, in the materials section, we
focus on MO semiconductors and high-k dielectrics for achieving high-performance flexible TFTs. In the
MO semiconductor subsection, we discuss the high mobility of indium tin zinc oxide (ITZO), ZnO:N,
LiZnO, etc., and multiple stack layers in detail. In the high-k dielectric subsection, we describe the impact
and effects of polymer dielectrics and high-k dielectrics on the performance of flexible TFTs. Thirdly, in the
fabrication process section, we examine the doping processes that significantly enhance the electrical