Non-volatile memory integrated circuit
View Patent ↗A nonvolatile memory integrated circuit arrayed in rows and columns is disclosed. Parallel lines of implant N-type regions are formed in a P-well of a semiconductor substrate, with lines of oxide material isolating each pair of the lines. Columns of memory cells straddle respective pairs of the implant region lines, with one line of the pair forming the source region and one line of the pair forming the drain region of each memory cell of the column. Each memory cell has a floating polysilicon storage gate. One of plural wordlines overlies each row of the memory cells. The portion of the wordline overlying each memory cells forms the control gate of the memory cell. Programming and erase operations occur by Fowler-Nordheim tunneling of electrons through a tunnel oxide layer between the floating gate and the source of the cell.
1. A semiconductor device comprising:
a first region of a first conductivity type in a semiconductor substrate;
at least one pair of parallel implant region lines of a second conductivity type in said first region; and
for each pair of parallel implant region lines, a column of plural non-volatile memory cells overlapping the respective pair of implant region lines, wherein one of the implant region lines of the pair includes a respective source region for each of the memory cells of the column, and the other implant region line of the pair includes a respective drain region for each of the memory cells of the column, with a respective subportion of the first region between the source and drain region of each of the memory cells comprising a channel region for the respective memory cell, wherein each of the non-volatile memory cells comprises:
a tunnel dielectric layer in contact with one of the implant region lines of the pair of implant region lines;
an electrically isolated floating gate over and in contact with the tunnel dielectric layer and extending only part of a distance between the source and drain regions;
a dielectric structure over and in contact with the floating gate and extending only part of the distance between the source and drain regions;
a control gate over and in contact with the dielectric structure and extending the entire distance between the source and drain regions; and
a gate dielectric layer between the control gate and a surface of the first region.
2. The semiconductor device of claim 1 , wherein the tunnel dielectric layer is in contact with the implant region line that includes the source regions for the memory cells of the column.
3. The semiconductor device of claim 1 , wherein there are a plurality of said pairs of parallel implant region lines in the first region, a plurality of the columns of the non-volatile memory cells, and a plurality of rows of the non-volatile memory cells across said columns, and further comprising:
a plurality of parallel dielectric isolation region lines parallel to the implant region lines, wherein one of the dielectric isolation region lines is between adjacent said columns of the memory cells; and
a plurality of parallel conductive wordlines extending perpendicularly across the implant region lines, wherein each said wordline integrally overlies the memory cells of one of the rows of the memory cells and the dielectric isolation region line between adjacent memory cells of the row, and a respective subportion of the wordline is the control gate for each of the respective memory cells of the row.
4. The semiconductor device of claim 3 , further comprising a row decoder circuit coupled to each of the plurality of wordlines.
5. The semiconductor device of claim 3 , further comprising a plurality of main bitlines, a plurality of first pass transistors, and a plurality of second pass transistors, and a main bitline decoder circuit coupled to the main bitlines,
wherein for each column of non-volatile memory cells, the implant region line including the drain regions is coupled to a respective one of the main bitlines of though one of the first pass transistors, and the implant region line including the source regions is coupled to a reference voltage source through one of the second pass transistors.
6. The semiconductor device of claim 1 , wherein there are a plurality of the pairs of implant region lines and a plurality of the columns of non-volatile memory cells; and
further comprising a plurality of wordlines each extending transversely to the pairs of implant region lines, with each said wordline integrally overlying an entire row of the non-volatile memory cells,
wherein a respective subportion of the wordline is the control gate for each of the respective memory cells of the row.
7. The semiconductor device of claim 6 , further comprising a plurality of main bit lines, wherein each of said implant region line comprising the drain regions of each said column is coupled to the one of the main bitlines through a pass transistor.
8. The semiconductor device of claim 7 , wherein the implant region line comprising the drain regions of each respective said column includes only a single contact, and the associated implant region line comprising the source regions of the column includes only a single contact.
9. The semiconductor device of claim 7 , wherein the implant region line comprising the drain regions of each respective said column includes only a single coupling to a main bit line, and the associated implant region line comprising the source regions of the column includes only a single coupling to a reference voltage source.