3d semiconductor device and structure

A method to form a 3D semiconductor device, the method comprising:

• providing a first level comprising a first single crystal layer and first single crystal transistors;
• forming a first metal layer, said first metal layer interconnecting said first single crystal transistors;
• forming second transistors atop of said first single crystal transistors;
• forming third transistors atop of said second transistors;
• forming fourth transistors atop of said third transistors;
• and then processing said device to at least replace said fourth transistor gates,
• wherein said replace said fourth transistor gates comprises processing to replace a non-metal gate material with a metal based gate material.

A 3D semiconductor device, the device comprising:

• a first level comprising a first single crystal layer and first single crystal transistors;
• a first metal layer interconnecting said first single crystal transistors;
• second transistors disposed atop of said first single crystal transistors;
• third transistors disposed atop of said second transistors;
• and
• fourth transistors disposed atop of said third transistors,
• wherein said second transistors and said third transistors are self-aligned, being processed following the same lithography step,
• wherein said fourth transistors comprise replacement gates,
• wherein said replacement gates comprise being processed to replace a non-metal gate material with a metal based gate material.