| 摘要 |
A MOSFET device is formed on a lightly doped semiconductor substrate, starting by forming a first dielectric layer on the substrate; forming a mask with an array of openings therein over the dielectric layer, and forming thick silicon dioxide regions through openings in the mask. Dopant is ion implanted into the substrate through the mask between the thick silicon dioxide regions to form an array of buried bitline conductors. Perform an etch back through the mask of the thick silicon dioxide regions removing material to form channel openings in the thick silicon dioxide regions down to the substrate. Then deposit a gate oxide layer over the exposed substrate, forming a conformal array of conductors over the device extending down into the channel openings forming sidewalls therein narrowing the channel openings. Then, form a ROM code mask over the device with a ROM code opening over one of the channel openings; and ion implant dopant into the ROM code opening.
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