High density dual-active-device-layer (DUAL)-CMOS structure with vertical tungsten plug-in wirings

A dual-active-device-layer (DUAL)-CMOS structure has been developed for achieving high-density LSIs. It consists of NMOSFETs in a lower bulk-Si and PMOSFETs in an upper SOI film. The most important structural feature is that upper PMOSFET electrodes are directly interconnected to lower NMOSFET electrodes using a vertical tungsten plug-in wiring technique. The plug-in wirings allow the device area to be reduced to approximately 50% that of a conventional bulk-Si CMOS. The contact resistance of the plug-in wiring for the upper and lower MOSFETs did not affect the MOSFET characteristics. It was confirmed that the propagation delay time of a 43-stage ring oscillator was about 10% faster than that for a conventional bulk-Si CMOS.<>