A method of operating a memory cell comprises applying a first procedure (typically erase) to establish a low threshold state including a first bias arrangement causing reduction in negative charge in the charge trapping structure, and a second bias arrangement tending to the induce balanced charge tunneling between the gate and the charge trapping structure and between the charge trapping structure in the channel. A second procedure (typically program) is used to establish a high threshold state in the memory cell, including a third bias arrangement that causes an increase in negative charge in the charge trapping structure.