Memory devices with diodes and methods for manufacturing the same

A memory device, comprising:

• a well formed in a substrate and extending along a first lateral direction, wherein the well has a first conductive type;
• a plurality of epitaxial structures disposed over the well, wherein the plurality of epitaxial structures have a second conductive type opposite to the first conductive type;
• a plurality of gate structures extending along a second lateral direction perpendicular to the first lateral direction, wherein each of the plurality of epitaxial structures is disposed next to a corresponding one of the plurality of gate structures along the first lateral direction;
• and
• a common epitaxial structure disposed over the well, wherein the common epitaxial structure has the first conductive type and is in contact with the well;
• wherein a first group of the plurality of epitaxial structures are each in contact with the well, and a second group of the plurality of epitaxial structures each have a bottom surface separated from the well with a corresponding dielectric layer.

A method for forming memory devices, comprising:

• forming a well in a substrate, wherein the well extends along a first lateral direction and has a first conductive type;
• forming an active region over the well, wherein the active region extends along the first lateral direction;
• forming a plurality of gate structures over the active region, wherein the plurality of gate structures extend along a second lateral direction perpendicular to the first lateral direction;
• forming a dielectric layer in a first portion of the well, with a second portion and a third portion of the well exposed;
• forming a common epitaxial structure to contact the second portion of the well, wherein the common epitaxial structure has the first conductive type;
• forming a first epitaxial structure separated apart from the well with the dielectric layer, wherein the first epitaxial structure has a second conductive type;
• and
• forming a second epitaxial structure to contact the third portion of the well, wherein the second epitaxial structure has the second conductive type.