Flash memory device including a buried floating gate and a buried erase gate and methods of forming the same

A method of forming a flash memory device, comprising:

• forming a first opening in a substrate semiconductor layer having a doping of a first conductivity type;
• forming a tunneling dielectric and a floating gate electrode in the first opening;
• forming a second opening in the substrate semiconductor layer adjacent to the first opening such that a sidewall of the tunneling dielectric is physically exposed;
• forming an erase gate dielectric and an erase gate electrode in the second opening;
• forming a control gate dielectric and a control gate electrode above a horizontal plane including a top surface of the substrate semiconductor layer;
• and
• forming at least two active regions within the substrate semiconductor layer by implanting dopants having a doping of a second conductivity type.

A method of forming a flash memory device, comprising:

• forming a first opening in a substrate semiconductor layer having a doping of a first conductivity type;
• forming a tunneling dielectric and a floating gate electrode in the first opening;
• forming a second opening in the substrate semiconductor layer adjacent to the first opening, wherein the second opening is laterally offset from the first opening along an axial direction;
• forming an erase gate dielectric and an erase gate electrode in the second opening;
• forming a control gate dielectric and a control gate electrode above a horizontal plane including a top surface of the substrate semiconductor layer;
• and
• forming at least two active regions within the substrate semiconductor layer by implanting dopants having a doping of a second conductivity type, wherein the at least two active regions comprises an axial active region that is laterally offset from the floating gate electrode along the axial direction, and a lateral active region that is laterally offset from the floating gate electrode along a lateral direction that is different from the axial direction.