This study investigates the response of synchronous dynamic random access memories to energetic electrons, and especially the possibility of electrons to cause stuck bits in these memories. Three different memories with different node sizes (63, 72 and 110~nm) were tested. Electrons with energies between 6~MeV and 200~MeV were used at RADEF in Jyväskylä, Finland, and at VESPER in CERN, Switzerland. Photon irradiation was also performed in Jyväskylä. In these irradiation tests, stuck bits originating from electron-induced single event effects were found, as well as single bit-flips from single electrons. To the best knowledge of the authors, this is the first time that stuck bits from single electron-events has been reported in the literature. \textcolor{black}{It is argued in the paper that the single event bit-flips and stuck bits are caused by the same mechanism, large displacement damage clusters, and that they represent different amounts of damage to the memory cell. After a large particle fluence, a rapid increase in the error rate was observed, originating from the accumulation of smaller displacement damage clusters in the memory cells.} The 110~nm memory was a candidate component to fly on the ESA JUICE mission, so the single event effect cross section as a function of electron energy was compared to the expected electron environment encountered by JUICE to estimate the error rates during the mission.