Origin of memory traps in chemically vapor‐deposited silicon nitride films was investigated. Electron‐spin resonance and infrared absorption measurements revealed the existence of silicon dangling bonds which have three‐folded configuration. Correlation between the spin density and the metal‐nitride‐oxide‐semiconductor (MNOS) memory characteristics was studied, and it was suggested that silicon dangling bonds are responsible for the trap states which cause not only hopping conduction, but also memory behavior. A model is presented suggesting that the dangling bonds are positively, neutrally, or negatively ionized. The MNOS memory behavior and the energy level of the traps were well interpreted by taking into account the transition of the dangling bonds.