Method of operating multi-level cell

A method of operating a multi-level cell (MLC) that comprises a substrate of a first conductivity type, a control gate, a charge-storing layer between the substrate and the control gate and two source/drain (S/D) regions of a second conductivity type, comprising an erasing step that injects charges of a first type into the charge-storing layer and a programming step that utilizes a double-side bias band-to-band tunneling hot hole (DSB-BTBTHH) effect and comprises:

• applying a first voltage to the substrate, a second voltage to both of the S/D regions and a third voltage to the control gate, wherein
• a difference between the first and second voltages is sufficient to cause band-to-band tunneling hot holes, and the third voltage causes charges of a second type to enter the charge-storing layer and can have 2n−1 (n≧2) different values, for programming the cell to a predetermined state among 2n−1 storage states.