Three-dimensional semiconductor device and method of fabrication

A semiconductor device comprising:

• a first layer of nanowires;
• a second layer of nanowires positioned above the first layer of nanowires;
• a third layer of nanowires positioned above the second layer of nanowires, wherein the first layer of nanowires, the second layer of nanowires, and the third layer of nanowires include nanowire portions positioned within a source-drain region of a semiconductor device;
• a first electrode that connects the first layer of nanowires and is routed through the source-drain region to a first position above the source-drain region;
• a second electrode that connects the second layer of nanowires and is routed through the source-drain region to a second position above the source-drain region;
• a third electrode that connects the third layer of nanowires and is routed through the source-drain region to a third position above the source-drain region;
• wherein the first contact structure is step-shaped with a portion of the second contact structure positioned above a horizontal surface of the underlying electrode structure.

A method of forming a semiconductor device, the method comprising:

• providing a substrate defining an initial connection area, the substrate having at least three nanowires positioned within the initial connection area, the nanowires being uncovered, the nanowires having a longitudinal axis that extends in a horizontal direction, the nanowires being positioned in a vertical stack and spaced apart from each other, the nanowires including a first nanowire, a second nanowire, and a third nanowire, the second nanowire being positioned above the first nanowire, and the third nanowire being positioned above the second nanowire;
• forming a first electrode that covers the first nanowire and extends vertically to a top of the initial connection area, the first electrode having a step-shaped cross-section;
• forming a second electrode that covers the second nanowire and extends vertically to a top of the initial connection area;
• and
• forming a third electrode that covers the third nanowire and extends vertically to a top of the initial connection area.