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From: cjp@megatek.UUCP (Chris Pikus)
Newsgroups: comp.arch
Subject: Dram Capacitance (was Questions about DRAM's)
Message-ID: <345@winston.megatek.uucp>
Date: 7 Apr 90 22:28:48 GMT
References: <28686@cup.portal.com>
Organization: Megatek Corporation, San Diego, Ca.
Lines: 30

From article <28686@cup.portal.com>, by mmm@cup.portal.com (Mark Robert Thorson):
> 
> Or, will SRAM's eventually surpass DRAM's in density?  I've heard this 
> comparison:  how small can you make a capacitor / how small can you make
> six transistors.  Will transistors eventually become so small that six
> interconnected transistors together are smaller than a minimum-size
> capacitor.  Or will the capacitors scale down as far as transistors
> can go?
>
	A physicist freind explained it to me once. He says that in 
order to make a memory cell, you need capacitance. (Whether in a capa-
citor or in the junction capacitance of a transistor.) A laymans 
interpretation is that capacitive delays are needed in the static
memory cell since the stability of the "D flip-flop" (static memory
cell) depends on the feedback elements from the output. 

	Granted this minimum capacitance is much smaller than what
is in a current capacitor today, but there is a quantum limit.

	A VLSI expert may want to correct me if I am wrong but I 
was under the impression that the "capacitor" in a DRAM was merely
a degenerate form of a standard VLSI transistor (i.e. using the 
junction capacitance of the FET as the cap.) Thus, capacitors should
scale as far as transistors.

-- 
Regards,
Christopher J. Pikus,          Megatek Corp.
INTERNET:     cjp@megatek      San Diego, CA
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