Hands-on: your first transistor

Reading is over. You are now a chip designer. Open the Chip Builder in a second tab and follow the six steps below. We'll build a silicon MOSFET — the same device pattern Intel and TSMC have shipped trillions of.

Try It Yourself

Open the Chip Builder

Pop the builder open in a new tab so you can switch back and forth.

Open Chip Builder

Transistor = water valve

Source pipe in. Drain pipe out. A valve handle (the gate) decides whether water flows. Build the pipes first, then the valve, then wire up the controls.

Step 1 — Place the substrate (Layer 1)

The substrate is the foundation. It holds every other layer and provides electrical isolation. Drag a Silicon Substrate from the library onto Layer 1 of the canvas. (We're starting with silicon on purpose — that's our baseline to beat.)

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Do it now: place Silicon Substrate

Switch to the Chip Builder, click 'Guided Build' if you want step-by-step help, and drop a Silicon Substrate on Layer 1.

Place substrate

Checkpoint · +5 XP

Why does every chip start with a substrate?

Step 2 — Place the silicon channel (Layer 2)

The channel is the highway electrons travel down. For our baseline we use silicon — mobility ~1400 cm²/Vs, well understood, the entire industry standard. Drop a Silicon Channel on Layer 2, directly on top of the substrate.

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Do it now: place Silicon Channel

Layer 2 sits on top of Layer 1. Center the channel over your substrate.

Place channel

Step 3 — Gate oxide + metal gate (Layer 3)

The gate is the valve handle. Two pieces: a thin SiO₂ gate oxide (the insulator that lets the gate's electric field reach into the channel without leaking current) and a Metal Gate on top. Place both on Layer 3, centered over the channel.

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Do it now: place gate stack

Place the SiO₂ Gate Oxide first, then a Metal Gate directly on top.

Place gate

Checkpoint · +5 XP

Why does the gate need an *insulator* (SiO₂) under the metal?

Step 4 — Source and drain contacts (Layer 4)

Source is where electrons enter. Drain is where they exit. Place a Source Contact at the left end of the channel and a Drain Contact at the right end. They should bracket your gate.

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Do it now: place source + drain

Source on the left, drain on the right — both touching the channel.

Place contacts

Step 5 — Wire it up

Switch to the Wire tool in the toolbar. Connect: Source → Channel (left edge), Channel (right edge) → Drain, and Gate → top of Channel. Connection order matters: the wires define which terminal does what.

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Do it now: wire the device

Three wires, in this order: Source→Channel, Channel→Drain, Gate→Channel.

Wire it

Step 6 — Power on

Hit the Power button in the toolbar. You should see green dots streaming from source to drain through the channel — that's electron flow under gate control. Congratulations: you just built and powered a working MOSFET.

Diagram · Reference build

animated

Click the gate to toggle the transistor

Your build should look roughly like this cross-section: substrate at the bottom, channel above, gate stack on top, source + drain bracketing the channel.

Try It Yourself

Power it on

Press Power. Watch the electrons flow. If nothing moves, check your wires.

Power on

You just built your first transistor. It's silicon — the industry baseline. In Lesson 2, we'll upgrade every layer to crystal materials and watch the performance jump.

Lesson Summary

Build a working silicon MOSFET from scratch in the Chip Builder.
Learn the six placement steps in the order real fabs use them.
Power it on and watch electrons flow.
Sets the silicon baseline you'll beat in later lessons.

Test Your Knowledge · +70 XP

Which layer holds the substrate?

Why is a thin oxide placed between the metal gate and the channel?

Source and drain are on which layer in this build?

What does the gate control?

Why are we starting with silicon, not crystal materials?