Active solid-state devices (e.g. – transistors – solid-state diode – Gate arrays – Having specific type of active device
Reexamination Certificate
2006-08-31
2008-10-21
Lindsay, Jr., Walter L (Department: 2812)
Active solid-state devices (e.g., transistors, solid-state diode
Gate arrays
Having specific type of active device
C257S206000, C257SE29257
Reexamination Certificate
active
07439559
ABSTRACT:
A method of forming a memory cell having a trench capacitor and a vertical transistor in a semiconductor substrate includes a step of providing a bonded semiconductor wafer having a lower substrate with an [010] axis parallel to a first wafer axis and an upper semiconductor layer having an [010] axis oriented at forty-five degrees with respect to the wafer axis, the two being connected by a layer of bonding insulator; etching a trench through the upper layer and lower substrate; enlarging the lower portion of the trench and converting the cross section of the upper portion of the trench from octagonal to rectangular, so that sensitivity to alignment errors between the trench lithography and the active area lithography is reduced. An alternative version employs a bonded semiconductor wafer having a lower substrate formed from a (111) crystal structure and the same upper portion. Applications include a vertical transistor that becomes insensitive to misalignment between the trench and the lithographic pattern for the active area, in particular a DRAM cell with a vertical transistor.
REFERENCES:
patent: 2004/0195622 (2004-10-01), Hwang et al.
Cheng Kangguo
Divakaruni Ramachandra
Radens Carl J.
Capella Steven
International Business Machines - Corporation
Lindsay, Jr. Walter L
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