Low-energy proton-induced single event upsets (SEUs) are a significant threat to the reliability of nanometer technologies, which are used in radiation environments. In this paper, through a developed program using Geant4 simulation toolkit, the effect of proton energies (<10 MeV) and angles of incidence (0∘ to 60∘), as well as isotropic radiation field on the SEU cross-section in a 65 nm CMOS SRAM, is studied. Furthermore, we have investigated the role of dominant physical mechanisms contributing to inducing SEUs. To analyze the responsible mechanisms for the upsets, proton interactions with BEOL of the device are considered to determine which particles could cause the upsets.The results show that for all investigated cases, the SEU cross-sections first increase for protons with incident energies of less than about 1 MeV and then decrease for higher energy protons. It is also observed that with increasing the tilt angle up to 45∘, the SEU cross-section increases, and the SEU peak shifts to higher energies, while for larger angles, the cross-section decreases. The results for the isotropic proton field show that the SEU peak occurs in lower energies compared to the fixed angle cases. We have also observed that for the proton energies corresponding to the SEU cross-section peak, the energy spectrum of the protons entering the sensitive volume confirms the occurrence of the Bragg peak inside the sensitive volume. Regarding the physical mechanisms responsible for SEU, the results show that for protons with energies of less than 1 MeV, direct ionization and for energies between 2 MeV and 10 MeV, recoiled Si ions due to elastic scattering of protons in the sensitive volume are dominant in inducing upsets. Our findings have also revealed that for proton energies of more than 5 MeV, other particles produced in BEOL such as oxygen and alpha particles also play a role to induce upsets, but have less contribution. These results indicate that the structures of the BEOL in advanced CMOS technologies can play an important role in inducing upsets for the upper limit of low energy protons. These considerations can be useful for designing advanced technologies more hardened against radiation. In general, we have found that for low energy protons, the proton-induced SEU cross-section of the device is a strongly correlated function of energy and direction of the incident protons.