semiconductor devices

What is it?

Semiconductor devices are the individual electrical structures built from the materials above: diodes, transistors (MOSFET, FinFET, and the emerging gate-all-around GAAFET), CMOS logic pairs, power devices, sensors, and memory cells.

How does it work?

A MOSFET controls current flow between source and drain by applying voltage to a gate separated from the channel by a thin dielectric — turning the channel "on" or "off" (or somewhere between, for analog use). As process nodes shrank, the planar MOSFET's gate lost effective control over a channel that was becoming too short and too thin; FinFETs respond by wrapping the gate around three sides of a raised silicon fin, and GAAFETs go further, wrapping the gate on all sides of one or more stacked nanosheets, both aimed at maintaining electrostatic control as devices scale down. CMOS pairs an n-type and p-type transistor so that, in steady state, one is always off — the basis of low-static-power digital logic. Power devices trade switching speed for the ability to block high voltage and carry high current; memory cells (SRAM, DRAM, and non-volatile variants) trade speed and density against each other depending on whether a bit is held by a latch, a capacitor, or a physical state change.

Why does it matter?

The device is where materials science becomes a controllable electrical switch or storage element — the smallest unit every larger digital or analog function is ultimately built from.

How does it connect to the next layer?

A single device does nothing on its own. Chip design is the discipline of arranging billions of these devices into architectures that compute, store, and communicate.