Reference cell for high speed sensing in non-volatile memories

摘要

A reference cell for use in a high speed sensing circuit includes a first sub-circuit and a second sub-circuit. The first sub-circuit has a structure similar to memory cells within odd number rows of a main memory array. The second sub-circuit has a structure similar to memory cells within even numbered rows of the main memory array. If a target cell within the main memory array lies within an odd numbered row, then the first sub-circuit is selected, and if the target cell lies within an even numbered row, then second sub-circuit is selected. Both of the first and second sub-circuits include a reference transistors having its control gate broken into two parts. A first part is a poly 1 layer and is separated from the channel region by a tunneling oxide. A second part is a metal or poly 2 layer over the first part and separated from the first part by a gate oxide. A via is used to connect the first part to the second part.