Single-event effects (SEEs) induced by heavy ions and high-energy protons have long been recognized as the primary causes of electronic system failures in spacecraft. However, in the space orbital environment, electrons typically exhibit higher flux and stronger shielding penetration capabilities than protons. Furthermore, at the nanoscale, electrons have been proven capable of inducing single-event upsets (SEUs) in devices. Electron-induced SEEs have emerged as a new issue affecting the reliability of spacecraft electronic systems. Research in this area is still in its infancy, and there is no consensus yet on the primary physical mechanisms of electron-induced SEEs. In this paper, based on 28-nanometer bulk silicon devices, we reveal the physical mechanisms and characteristics of electron-induced SEEs through Monte Carlo simulations and electron irradiation experiments. The results indicate that direct ionization is the main physical mechanism for electron-induced SEUs when the device's critical charge is less than 0.3 fC or the electron energy is less than 100 MeV. The energy and cross-section of secondary electrons generated by direct ionization of electrons in materials are minimally influenced by the initial electron energy. Therefore, when direct ionization is the primary mechanism, the SEU cross-section remains almost unaffected by the incident electron energy. Only when the device's critical charge is greater than 0.4 fC and the electron energy exceeds 1000 MeV do the recoil nuclei generated by elastic collisions between electrons and atomic nuclei, as well as the secondary particles produced by electron-induced nuclear reactions, become important factors in inducing SEUs. In such cases, indirect ionization becomes a significant mechanism for electron-induced SEUs and the SEU cross-section increases with higher incident electron energy. Compared to perpendicular incidence, electrons incident at smaller angles result in a larger SEU cross-section when the device's critical charge is low. However, the influence of the electron incidence angle on the SEU cross-section diminishes as the device's critical charge increases. As the device's critical charge decreases, the SEU cross-sections induced by electrons of various energies increase exponentially. When the device's critical charge is less than 0.2 fC, the contribution of electrons to SEUs in typical Earth orbits exceeds that of protons. Therefore, direct ionization is the most critical physical mechanism of electron-induced SEUs.