Semiconductor memory array of floating gate memory cells with program/erase and select gates
View Patent ↗A memory device, and method of making and operating the same, including a substrate of semiconductor material of a first conductivity type, first and second spaced apart regions in the substrate of a second conductivity type with a channel region therebetween, an electrically conductive floating gate having a first portion disposed over and insulated from the channel region and a second portion disposed over and insulated from the first region and including a sharpened edge, an electrically conductive P/E gate having a first portion disposed over and insulated from the first region and a second portion extending up and over the floating gate second portion and insulated therefrom by a first layer of insulation material, and an electrically conductive select gate having a first portion disposed laterally adjacent to the floating gate and disposed over and insulated from the channel region.
1. An electrically programmable and erasable memory device, comprising:
a substrate of semiconductor material of a first conductivity type;
first and second spaced-apart regions in the substrate of a second conductivity type, with a channel region therebetween;
an electrically conductive floating gate having a first portion disposed over and insulated from the channel region, and a second portion disposed over and insulated from the first region and including a sharpened edge;
an electrically conductive P/E gate having a first portion disposed over and insulated from the first region, and a second portion extending up and over the floating gate second portion and insulated therefrom by a first layer of insulation material; and
an electrically conductive select gate disposed laterally adjacent to and insulated from the floating gate and disposed over and insulated from the channel region;
wherein the sharpened edge is formed at an intersection of a sloping upper surface of the floating gate and a side surface of the floating gate;
wherein:
the select gate is insulated from the channel region by a second layer of insulation material;
the floating gate is insulated from the channel region and the first region by a third layer of insulation material; and
the P/E gate first portion is insulated from the first region by the first and third layers of insulation material.
2. The device of claim 1 , wherein each of the first, second and third layers of insulation material have a thickness that is different from a thickness of the others of the first, second and third layers of insulation material.
3. An array of electrically programmable and erasable memory devices comprising:
a substrate of semiconductor material of a first conductivity type;
spaced apart isolation regions formed on the substrate which are substantially parallel to one another and extend in a first direction, with an active region between pair of adjacent isolation regions;
each of the active regions including pairs of memory cells, each of the memory cell pairs including:
a first region and a pair of second regions spaced apart in the substrate having a second conductivity type, with channel regions formed in the substrate between the first region and the second regions,
a pair of electrically conductive floating gates each having a first portion disposed over and insulated from one of the channel regions,and a second portion disposed over and insulated from the first region and including a sharpened edge, wherein for each of the floating gates, the sharpened edge is formed at an intersection of a sloping upper surface of the floating gate and a side surface of the floating gate.
an electrically conductive P/E gate having a first portion disposed over and insulated from the first region, and a pair of second portions each extending up and over one of the floating gate second portions and insulated therefrom by a first layer of insulation material, and
a pair of electrically conductive select gates each disposed laterally adjacent to and insulated from one of the floating gates and disposed over and insulated from the channel region;
wherein for each of the memory cells:
the select gate is insulated from the channel region by a second layer of insulation material;
the floating gate is insulated from the channel region and the first region by a third layer of insulation material; and
the P/E gate first portion is insulated from the first region by the first and third layers of insulation material.
4. The array of claim 3 , wherein for each of the memory cells, each of the first, second and third layers of insulation material have a thickness that is different from a thickness of the others of the first, second and third layers of insulation material.
5. The array of claim 3 wherein each of the P/E gates is formed as part of a conductive P/E gate line that extends across the active regions and isolation regions in a second direction substantially perpendicular to the first direction, and wherein each of the P/E gate lines intercepts one of the PIE gates in each of the active regions.
6. The array of claim 5 , wherein each of the select gates is formed as part of a conductive word line that extends across the active regions and isolation regions in the second direction, and wherein each of the word lines intercepts one of the select gates in each of the active regions.
7. The array of claim 6 , wherein each of the active regions further comprises;
a conductive bit line electrically connected to each of the second regions in the active region.