Method of making self-aligned remote polysilicon contacts

DETAILED DESCRIPTION In accordance with the present invention, shallow source and drain contacts are produced by the steps of (1) depositing a polysilicon layer over the entire surface of a semiconductor device having source and drain regions, a gate, and oxide spacers which may also contain LDD regions, and (2) chemi-mechanically polishing the resulting polysilicon layer, the gate, and the oxide spacers to remove a portion of the polysilicon layer, along with portions of the gate, and the oxide spacers.
By applying a polysilicon layer overall and then using chemi-mechanical polishing to remove polysilicon from areas on the surface of the transistor where it is undesired, such as from the gate and oxide spacers, the polysilicon layer is converted into two or more remote contacts.
Chemi-mechanical polishing also reduces the thickness of the polysilicon remaining on the surface of the transistor.
The net result is the provision of ultra-shallow polysilicon contacts electrically isolated from one another.
Since the polysilicon can be removed with any desired degree of precision by chemi-mechanical polishing, the problems associated with photolithographic processes are no longer present.
As noted above photolithographic processing does not provide a sufficiently high degree of precision to provide the structures having sufficiently small dimensions.
The present invention in effect achieves automatic alignment of ultra-shallow electrical contact regions with source and drain regions without adversely affecting the electrical isolation achieved by use of oxide spacers.