Each memory cell is of the type with charge trapping in a dielectric interface and includes a state transistor selectable by a vertical selection transistor buried in a substrate and comprising a buried selection gate. The columns of memory cells include pairs of twin memory cells. The two selection transistors of a pair of twin memory cells have a common selection gate and the two state transistors of a pair of twin memory cells have a common control gate. The device also includes, for each pair of twin memory cells, a dielectric region situated between the control gate and the substrate and overlapping the common selection gate so as to form on either side of the selection gate the two charge-trapping dielectric interfaces respectively dedicated to the two twin memory cells.