Transistor structures and methods for forming the same

A transistor structure, comprising:

• a gate electrode layer;
• an active layer comprising a semiconductor material;
• a gate insulator layer between the gate electrode layer and the active layer;
• a dielectric material layer over the active layer;
• a first electrode extending through the dielectric material layer and at least partially into the active layer;
• a first carrier injection layer laterally surrounding the first electrode and contacting side surfaces of the dielectric material layer and the active layer;
• and
• a second carrier injection layer laterally surrounding the first electrode, wherein the second carrier injection layer is located between the first carrier injection layer and the first electrode, the first carrier injection layer comprises a metal oxide material comprising indium and at least one additional metal, and the first carrier injection layer has an amorphous structure, and the second carrier injection layer has a composition that is different than the first carrier injection layer.

A method of fabricating a transistor structure, comprising:

• forming an active layer comprising a semiconductor material;
• forming a dielectric material layer over the active layer;
• forming a pair of openings through the dielectric material layer and at least a portion of the active layer;
• forming a carrier injection layer over sidewalls and a bottom surface of each opening of the pair of openings;
• and
• depositing a conductive material over the carrier injection layer within each of the openings to form a source electrode and a drain electrodes, wherein a bottom surface of the carrier injection layer within each of the openings is recessed relative to an upper surface of the active layer by a recess distance that is at least 30% of a total thickness of the active layer, and a work function of the carrier injection layer is between a work function of the active layer and a work function of the source electrode and drain electrode.