Abstract A newly integrated pulsed laser system has been utilized to investigate the effects of voltage stress on single event upset (SEU) of flip flop chain manufactured in 65 nm bulk CMOS technology. Laser mappings of the flip flop chain revealed that the SEU sensitive regions increased with laser energy. Post-processing of the data from the laser mapping facilitated the plotting of the cross-section versus laser energy curve. We found a clear shift in the cross-section curves after voltage stress of 130 h. Comparisons of data revealed at least a doubled increase in sensitive areas after voltage stress. During the voltage stress, various electrical parameters were monitored and changes were observed. It was found that the increase in SEU sensitivity is related to electrical parameter changes and SPICE simulation results concur likewise.