Connections from buried interconnects to device terminals in multiple stacked devices structures

Abstract

In vertically stacked device structures, a buried interconnect and bottom contacts can be formed, thereby allowing connections to be made to device terminals from both below and above the stacked device structures. Techniques herein include a structure that enables electrical access to each independent device terminal of multiple devices, stacked on top of each other, without interfering with other devices and the local connections that are needed.

1 . A method of forming a semiconductor device, the method comprising:
 forming a stack of nano-channels spaced vertically from each other;   forming a first interconnect line positioned below the stack of nano-channels;   creating a bottom contact that connects to the first interconnect line;   forming gate-all-around channels from the stack of nano-channels, wherein the gate-all-around channels form a stack of device tiers having at least three device tiers including a lower device tier, one or more intermediate device tiers stacked vertically over the lower device tier, and an upper device tier stacked vertically over the one or more intermediate device tiers;   connecting the first interconnect line to one or more first device terminals from the stack of device tiers using the bottom contact; and   connecting a second interconnect line to one or more second device terminals from the stack of device tiers using a top contact, the second interconnect line formed above the stack of device tiers.   
     
     
         2 . The method of  claim 1 , wherein the one or more first device terminals is a lower device terminal in the lower device tier. 
     
     
         3 . The method of  claim 1 , wherein the one or more first device terminals and the one or more second device terminals is a gate. 
     
     
         4 . The method of  claim 1 , wherein the one or more second device terminals is at least one of an upper device terminal in the upper device tier and an intermediate device terminal in the one or more intermediate device tiers. 
     
     
         5 . The method of  claim 4 , further comprising, in a case that the one or more second device terminals includes the intermediate device terminal, laterally extending the intermediate device terminal beyond a length of (1) the upper device terminal and (2) any additional intermediate device terminals from the one or more intermediate device tiers located above the intermediate