Abstract: The present invention is directed to a unique method for fabricating a silicon based MOS transistor having an inverse-T refractory metal gate structure. The gate fabricated according to this invention comprises a main CVD tungsten portion and a lower sputtered tungsten portion outwardly extending from the bottom of the CVD portion such that a cross section of the gate appears as an inverted "T". A Cl.sub.2 /O.sub.2 plasma etch is used to etch the CVD tungsten layer and a chemical etch is used to etch the sputtered tungsten layer to form the gate electrode. It has been discovered that sputtered tungsten is more resistant to Cl.sub.2 /O.sub.2 reactive ion etch than is CVD tungsten. The sputtered tungsten layer acts as a shield to protect the underlying gate oxide layer from ion damage throughout the fabrication process.

Abstract: A high density, DRAM cell array with a very short channel, vertical gate transfer transistor that can be manufactured using conventional photolithography process steps. The conventional four-by-four DRAM array shown schematically in FIG. 1a is rearranged to the shared-gate, double-bit array shown schematically in FIG. 1b. Trench storage capacitors and vertical FET transistors are arranged in pairs with a common vertical gate and a common substrate, allowing both bit and substrate contacts to be shared by adjacent cells.

Abstract: A bonded, SOI wafer which has stepped isolation trenches and sublayer interconnections first formed in a bulk silicon wafer. After these process steps are complete, a thin polysilicon layer is formed on the planarized upper surface of the bulk silicon wafer. This thin polysilicon layer is then bound to an oxide layer on the surface of a separate wafer to form a bonded silicon-on-oxide structure. The entire assembly is, in effect inverted, and what had been the lower surface of the bulk silicon wafer, is removed to the bottom of the deepest trench step. In this bonded SOI structure, regions between the trenches are deep and suitable for bipolar device fabrication, while the trench steps form shallow regions suitable for fabrication of CMOS devices.

Abstract: A bonded, SOI wafer which has stepped isolation trenches and sublayer interconnections first formed in a bulk silicon wafer. After these process steps are complete, a thin polysilicon layer is formed on the planarized upper surface of the bulk silicon wafer. This thin polysilicon layer is then bound to an oxide layer on the surface of a separate wafer to form a bonded silicon-on-oxide structure. The entire assembly is, in effect inverted, and what had been the lower surface of the bulk silicon wafer, is removed to the bottom of the deepest trench step. In this bonded SOI structure, regions between the trenches are deep and suitable for bipolar device fabrication, while the trench steps form shallow regions suitable for fabrication of CMOS devices.

Abstract: A high density, DRAM cell array with a very short channel, vertical gate transfer transistor that can be manufactured using conventional photolithography process steps. The conventional four-by-four DRAM array shown schematically in FIG. 1a is rearranged to the shared-gate, double-bit array shown schematically in FIG. 1b. Trench storage capacitors and vertical FET transistors are arranged in pairs with a common vertical gate and a common substrate, allowing both bit and substrate contacts to be shared by adjacent cells.

Abstract: A subtractive method for making a Levenson type lithographic phase shift mask using a sacrificial etch monitor film in which some of the monitor film is left standing on the opaque portions of the mask. The monitor film otherwise is consumed when it is simultaneously etched with selected portions of the mask substrate to produce recesses of desired depth in the substrate. The etching is stopped upon detecting that the etched monitor film is completely consumed. The technique also is adapted for the fabrication of a RIM type lithographic phase shift mask combined with the Levenson type phase shift mask in the same mask. The technique further is adapted to include 90 degree shift transitions at the end of the Levenson line-space pairs of the mask. The monitor film left standing on the opaque portions of the mask provides self-aligned phase error correction to offset sidewall scattering in the Levenson type mask.

Abstract: A lateral bipolar transistor has an extrinsic base layer on either side of a centrally disposed emitter layer and an intrinsic base and a collector oriented perpendicularly to the extrinsic base and collector layers.

Abstract: A field effect transistor (FET) with a vertical gate and a very thin channel sandwiched between source and drain layers. In a preferred embodiment of the invention, the FET is formed on a silicon on insulator (SOI) substrate with the silicon layer serving as the first layer (e.g., the source layer). A low temperature epitaxial (LTE) process is used to form a very thin (e.g., 0.1 .mu.m) channel, and a chemically vapor deposited polysilicon layer forms the top layer (e.g., the drain layer). An opening is etched through the three layers to the insulator substrate and its wall is oxidized, forming a gate oxide. Polysilicon is deposited to fill the opening and form the vertical gate.

Abstract: A field effect transistor (FET) with a vertical gate and a very thin channel sandwiched between source and drain layers. In a preferred embodiment of the invention, the FET is formed on a silicon on insulator (SOI) substrate with the silicon layer serving as the first layer (e.g., the source layer). A low temperature epitaxial (LTE) process is used to form a very thin (e.g., 0.1 .mu.m) channel, and a chemically vapor deposited polysilicon layer forms the top layer (e.g., the drain layer). An opening is etched through the three layers to the insulator substrate and its wall is oxidized, forming a gate oxide. Polysilicon is deposited to fill the opening and form the vertical gate.

Abstract: A wafer structure suitable for the formation of semiconductor devices thereon and having a buried interconnect structure for interconnection of desired ones of the semiconductor devices according to a predetermined interconnection pattern and a method of making the same is disclosed. The wafer structure comprises a primary substrate having a first thickness appropriate for the formation of the desired semiconductor devices.