Electron drift mobility longitudinal to hydrogenated amorphous silicon/silicon nitride multilayer structures has been measured by the time‐of‐flight method. Transient photocurrent shows a clear kink corresponding to the transit time. The room‐temperature electron mobility in multilayer structures is smaller by three or four orders of magnitude than that observed in bulka‐Si:H. The room‐temperature electron mobility decreases with decreasing well layer width at constant layer thickness of 13 A˚, while the activation energy of the mobility increases. The lifetime of electrons tends to increase when the well layer thickness is reduced.