A new buried-oxide isolation for high-speed high-density MOS integrated circuits

Abstract

The BO-MOS has an extensive oxide-isolated structure which isolates not only the sidewall but also the bottom of the source and drain diffusions, similar to SOS-MOS, and yet it retains high carrier mobility and low-leakage junction properties. A 1024-bit static NMOS RAM is successfully fabricated using photomasks of a redesigned high-density bulk NMOS RAM (Fujitsu MBM8115). The ring oscillator circuit fabricated using existing SOS-CMOS photomasks shows an equivalent speed-power performance to the original SOS device. The fabrication sequence for the BO-MOS requires the same number of photomasks as for the conventional MOS devices.