Semiconductor memory

A semiconductor memory comprising:

• a semiconductor substrate having a channel region;
• a first tunnel insulating film formed on the channel region of the semiconductor substrate;
• a first fine particle layer formed on the first tunnel insulating film, the first fine particle layer comprising a plurality of first conductive fine particles that meet a Coulomb blockade condition;
• a second tunnel insulating film formed on the first fine particle layer;
• a second fine particle layer formed on the second tunnel insulating film, the second fine particle layer comprising a plurality of second conductive fine particles that meet the Coulomb blockade condition, wherein a mean particle diameter of the second conductive fine particles is larger than that of the first conductive fine particles;
• a third tunnel insulating film formed on the second fine particle layer;
• a third fine particle layer formed on the third tunnel insulating film, the third fine particle layer comprising a plurality of third conductive fine particles that meet the Coulomb blockade condition, wherein a mean particle diameter of the third conductive fine particles is smaller than that of the second conductive fine particles;
• a fourth tunnel insulating film formed on the third fine particle layer;
• a charge storage film formed on the fourth tunnel insulating film;
• a block insulating film formed on the charge storage film;
• and
• a gate electrode formed on the block insulating film.