Method for forming isolation in flash memory wafer

The present invention relates generally to computer flash memory systems, and more particularly to systems and methods for isolating flash memory elements. A method for making a self-aligned isolated memory core for a flash memory wafer includes the steps of establishing control gates for memory cells in the core by depositing a first polysilicon layer on a silicon substrate, etching the first layer, and depositing a second polysilicon layer on the substrate, with the polysilicon layers being separated by an interpoly dielectric layer. Then, after the control gates have been established, isolation trenches are formed in the silicon substrate between regions by self-aligned etching processes.