BIDIRECTIONAL READING OR PROGRAMMING NON-VOLATILE FLOATING GATE MEMORY CELL WITH INDEPENDENTLY CONTROLLABLE GATES, ARRAY THEREOF AND FORMING METHOD THEREOF TO INCREASE STORING DENSITY

摘要

PURPOSE: A bidirectional reading or programming non-volatile floating gate memory cell with independently controllable gates is provided to increase storing density by storing a plurality of bits in a single cell. CONSTITUTION: A substantially single crystalline semiconductor substrate material of the first conductivity type has a substantially flat surface. The first trench in the substrate has a substantially vertical sidewall and a base wall on the flat surface. The second trench in the substrate has a substantially vertical sidewall and a base wall on the flat surface. The first region of the second conductivity type is formed along the base wall of the first trench. The second region of the second conductivity type in the material is formed along the base wall of the second trench. A channel region includes the first portion along the sidewall of the first trench, the second portion along the sidewall of the second trench, and the third portion interconnecting the first and second regions to conduct charges. A dielectric is formed on the channel region. The first floating gate(40a) on the dielectric stores at least one of a plurality of bits. The second floating gate(40b) on the dielectric stores at least another bit. A gate electrode on the dielectric is separated from the third portion between the first and second portions. The first independently controllable gate electrode in the first trench is insulated from the first region. The second independently controllable gate electrode in the second trench is insulated from the second region.