---
title: "Full custom VLSI technology"
subject: "Embedded System"
chapter: 8
key: "semester_6/embedded_system:full-custom-vlsi-brief"
source: https://www.bctengineer.com/q/semester_6/embedded_system/full-custom-vlsi-brief
site: BCT Engineering
---

# Full custom VLSI technology

Embedded System · Chapter 8: IC Technology

- Asked in: 2075 Baisakh, 4 marks
- Video: [Module-4, Lecture-8, Microcontroller & Embedded System: Full Custom / VLSI, Semi Custom ASIC](https://www.youtube.com/watch?v=Z1CqrvEl0pE) — Dr. SANGITA ROY
- Answer checked by Claude Opus 5.5 (high effort) on 2026-10-14
- Page: https://www.bctengineer.com/q/semester_6/embedded_system/full-custom-vlsi-brief
- Whole chapter: https://www.bctengineer.com/md/semester_6/embedded_system/chapter-8

## Question

Describe briefly about Full custom VLSI technology.

## Short answer

Full-custom VLsI designs every transistor and interconnnect; all mask layers are custom. It delivers highest speed, lowest power and smallest area, but has very high NRE cost and long design time, used in high-volume chips like microprocessors.

## Answer

**Full-custom VLSI** is an IC technology in which the designer controls the layout of every transistor and interconnect, and all mask layers are made specifically for that chip.

- **Design flow:** specification, logic and circuit design, transistor sizing, manual layout (polygons for diffusion, poly, metal), design-rule check, extraction and simulation, mask generation, fabrication and test.
- **Advantages:** highest speed, lowest power, smallest area, lowest unit cost at very high volume, analog/digital mix possible.
- **Disadvantages:** very high NRE cost, long design time, needs expert layout engineers, errors require new masks, no change after fabrication.
- **Applications:** microprocessors, memories, high-volume consumer chips.

## Check yourself

The answer's key points as multiple-choice questions, with the correct option and why.

1. What is full-custom VLSI?
   A. A design using pre-made standard cells only
   B. A design where the layout of every transistor and interconnect is controlled and all masks are specific to the chip
   C. A chip programmed after fabrication
   D. A design with only metal layers custom
   Answer: B. The designer controls the layout of everything and all masks are made specifically for that chip. (Key point: Definition)

2. Which is an advantage of full-custom design?
   A. Low NRE cost
   B. Short design time
   C. Highest speed, lowest power and smallest area
   D. Easy changes after fabrication
   Answer: C. It gives the best speed, power and area, and low unit cost at very high volume. (Key point: Advantages)

3. Why is full-custom unsuitable for small volumes?
   A. It has very high NRE cost and long design time, and errors need new masks
   B. It is slow
   C. It uses too little area
   D. It cannot make memories
   Answer: A. The high NRE and long design time are spread only over high volume production. (Key point: Disadvantages)

4. Which step checks the manually drawn layout for rule violations?
   A. Mask generation
   B. Specification
   C. Packaging
   D. Design-rule check
   Answer: D. Design-rule check verifies the layout polygons before extraction, simulation and mask generation. (Key point: Design flow)

## Related in Embedded System

- [Full-custom IC advantages and disadvantages](https://www.bctengineer.com/question.md?key=semester_6%2Fembedded_system%3Afull-custom-pros-cons) — Embedded System, chapter 8, asked 2×
- [Full-custom, semi-custom and PLD design steps](https://www.bctengineer.com/question.md?key=semester_6%2Fembedded_system%3Afull-semi-custom-pld-steps) — Embedded System, chapter 8, asked 2×
- [Two categories of semi-custom IC](https://www.bctengineer.com/question.md?key=semester_6%2Fembedded_system%3Asemi-custom-two-categories) — Embedded System, chapter 8, asked 2×
- [Semi-custom ASIC and manufacturing steps](https://www.bctengineer.com/question.md?key=semester_6%2Fembedded_system%3Asemi-custom-asic-types-manufacturing) — Embedded System, chapter 8