Buried-oxide isolation with etch-stop (BOXES)

A buried-oxide (BOX) isolation process which has greatly improved submicrometer MOS manufacturability has been developed. The process, BOXES (BOX with etch-stop) isolation, incorporates an etch-stop layer over active area down to which the field oxide is etched, rather than to the active-area surface as in BOX. Nonuniformities inherent to the BOX process do not then cause the field oxide to be recessed below the active area surface. Furthermore, by a brief overetch of etch-stop during its patterning, the field oxide is made to controllably encroach laterally over the active-area edges. Measurements of NMOS devices demonstrate that BOXES isolation with lateral encroachment has greatly reduced sidewall and edge parasitic conduction.<>