Dual channel/gate vertical field-effect transistor (FET) for use with a perpendicular magnetic tunnel junction (PMTJ)

A method, comprising:

• forming a drain material above a substrate in a film thickness direction;
• forming and patterning a first masking layer above the drain material in the film thickness direction, the first masking layer being patterned to expose a portion of the drain material having a circular cross-section along a plane perpendicular to the film thickness direction;
• removing all portions of the drain material except for the exposed portion of the drain material and portions positioned directly therebelow in the film thickness direction using the first masking layer;
• removing the first masking layer during or after removal of the portions of the drain material;
• forming a first insulative layer above portions of the substrate not covered by the drain material to a thickness consistent with an upper surface of the drain material;
• forming a second insulative layer above the first insulative layer and the drain material in the film thickness direction to a desired thickness;
• placing the first masking layer above the second insulative layer aligned with previous placement of the first masking layer above the substrate to expose a portion of the second insulative layer having the circular cross-section along the plane perpendicular to the film thickness direction;
• removing the exposed portion of the second insulative layer to expose the upper surface of the drain material;
• removing the first masking layer during or after removal of the exposed portion of the second insulative layer;
• growing the second insulative layer along the plane perpendicular to the film thickness direction to shrink a diameter of a hole through the second insulative layer having the circular cross-section along the plane perpendicular to the film thickness direction;
• removing exposed portions of the drain material through the hole of the second insulative layer to form a drain contact having a circular cross-sectional hole in a center thereof along the plane perpendicular to the film thickness direction;
• removing the first insulative layer and the second insulative layer;
• removing portions of the substrate positioned directly below the drain contact to a desired level in the film thickness direction to form a channel having the circular cross-section with a hole in a center thereof along the plane perpendicular to the film thickness direction;
• forming gate dielectric layers above the drain contact and on sides of the drain contact and the channel, the gate dielectric layers having concentric circular cross-sections along the plane perpendicular to the film thickness direction, wherein the circular cross-section of the drain contact has one circular cross-sectional portion of the gate dielectric layers in direct contact on either side thereof;
• forming a source layer below the channel in the film thickness direction, the source layer being electrically coupled to the channel;
• forming and patterning a second masking layer above the gate dielectric layers positioned above the drain contact and above the hole in the center of the drain contact in the film thickness direction, wherein the second masking layer has a rectangular cross-section along the plane perpendicular to the film thickness direction that is positioned above a plurality of drain contacts;
• removing portions of the source layer and substrate not covered by the second masking layer in the film thickness direction to form a source line that is electrically coupled to a plurality of channels along the plane perpendicular to the film thickness direction;
• removing the second masking layer;
• forming a third insulative layer having a thickness in the film thickness direction that corresponds to a desired height of a lower surface of subsequently formed gate layers;
• forming the gate layers above the third insulative layer on sides of the gate dielectric layers to a thickness coincident with a lower surface of the drain contact in the film thickness direction, wherein an inner gate layer fills a hole through a center of a center concentric circular cross-section of the gate dielectric layers along the plane perpendicular to the film thickness direction, and wherein an outer gate layer surrounds an outside concentric circular cross-section of the gate dielectric layers along the plane perpendicular to the film thickness direction;
• removing an upper portion of the gate dielectric layers above the drain contact to expose an upper surface of the drain contact;
• forming an electrode above the upper surface of the drain contact;
• and
• forming a fourth insulative layer above the third insulative layer and the gate layers in the film thickness direction, and along sides of the electrode along the plane perpendicular to the film thickness direction.