As the feature size of the device decreases, the critical charge decreases gradually and the influence of radiation particles becomes more and more serious, especially the single event upset (SEU). Some previously unknown radiation damage began to appear as the size of the device decreased. Low energy protons undergoing direct ionization can induce SEU in 65 nm static random access memories (SRAM), and muons can induce errors as a function of incident muon energy. In this work, the radiation damage caused by X-ray to the 45 nm SRAM is studied through experiments. The sensitive volume of SRAM is constructed using Monte Carlo radiation transport code Geant4 to analyze the effects of critical charge and metal interconnect overlayers of different materials. The experimental results suggested that under the low power state, the secondary electrons produced by the X-ray can induce upsets, lower the voltage, and increase the number of errors. Monte Carlo simulation shows that as the critical charge decreased, SEU becomes more severe. At the same time, photons interact with high atomic number materials in the metal interconnect overlayers, which could generate more secondary electrons resulting in the SEU cross section rising to a higher value. [ABSTRACT FROM AUTHOR]