Split gate non-volatile memory cell having a floating gate, word line, erase gate, and method of manufacturing
A memory device including a silicon semiconductor substrate, spaced apart source and drain regions formed in the substrate with a channel region there between, and a conductive floating gate disposed over a first portion of the channel region and a first portion of the source region. An erase gate includes a first portion that is laterally adjacent to the floating gate and over the source region, and a second portion that extends up and over the floating gate. A conductive word line gate is disposed over a second portion of the channel region. The word line gate is disposed laterally adjacent to the floating gate and includes no portion disposed over the floating gate. The thickness of insulation separating the word line gate from the second portion of the channel region is less than that of insulation separating the floating gate from the erase gate.
1. A memory device, comprising:
a silicon semiconductor substrate;
spaced apart source and drain regions formed in the silicon semiconductor substrate with a channel region there between;
a conductive floating gate disposed over and insulated from a first portion of the channel region and a first portion of the source region;
a conductive erase gate that includes:
a first portion that is laterally adjacent to and insulated from the floating gate, and is over and insulated from the source region, and
a second portion that extends up and over, and is insulated from, the floating gate;
a conductive word line gate disposed over and insulated from a second portion of the channel region, wherein the word line gate is disposed laterally adjacent to the floating gate and includes no portion disposed over the floating gate;
wherein a thickness of insulation separating the word line gate from the second portion of the channel region is less than a thickness of insulation separating the floating gate from the erase gate, and wherein the erase gate second portion is the only conductive gate or conductive gate portion disposed over the floating gate.
2. The memory device of claim 1 , wherein the word line gate comprises:
a bottom surface facing the second portion of the channel region, wherein the bottom surface is planar; and
a top surface opposite the bottom surface, wherein the top surface is planar.
3. The memory device of claim 2 , wherein the erase gate comprises:
a bottom surface facing the source region; and
a top surface opposite the bottom surface that is planar.
4. The memory device of claim 1 , wherein the word line gate comprises:
metal material; and
a layer of high K dielectric material disposed between the metal material and the second portion of the channel region.
5. The memory device of claim 1 , wherein the word line gate comprises:
polysilicon; and
a layer of nitride oxide disposed between the polysilicon and the second portion of the channel region.