What is VLSI design

VLSI stands for Very Large Scale Integration. When you ask the question, we need to see from what standpoint you are asking this question. If you are asking to find out what all is within the scope of VLSI, one would have to say:
a. Specifications of architecture, protocols etc.
b. Logical expression of the architecture
c. Physical representation of the circuit
Each of these encompass some functions in the VLSI flow. If now you ask from the standpoint of an engineer working in the industry trying to find out what all is part of VLSI design, one will have to take one of the above three scopes and mention the areas of work functions:
a. Specifications – RTL coding, architecture design, Verification, DFT specifications and scan chain specifications etc.
b. Logical representation – Physical synthesis, P&R database, timing analysis, logical gate-level simulations for functional test vectors, DFT test-coverage statistics etc.
c. Physical representation – circuit design, layout design, DRC/LVS/DFM/ERC, electrical simulation/analysis results, local heating results, EMIR analysis results, ESD protection etc, packaging technology, ringing analysis of power in pad rings.
Things that are often incorrectly attributed to VLSI are:
a. MEMS – this is an aspect of technology that has not advanced enough to be used extensively across the chip. For example a NAND gate in the circuit is used so often that we don’t care how it functions anymore. MEMS technology is not at that stage as of today.
b. Device engineering, device physics, etc. – This is hard-core R&D. I would not consider work in VLSI as R&D, but as only development using existing tools and principles. Device physics is an area that is very far ahead of VLSI technology. Its results are used sometimes in VLSI, but more often than not, it involves experimental and theoretical physics – an area far removed from VLSI.
In summary, VLSI is the art of putting together many things to get an engineering solution to a problem in application. It does not necessarily involve inventing something new, but involves a lot of replication of circuits and functionality and sometimes some innovative implementation of the functionality.
VLSI stands for Very Large Scale Integration and if I’d describe it in simple words, I’d say it’s the gathering up of a very large number of transistors making up circuits for a certain functionality, that’s implemented on a chip.