Why is this a component? Couldn't you just make one of these out of PCB traces?

Certainly not at these frequencies and corresponding high capacitance values; getting 22nF out of a PCB even with ECM would require quite a large surface area and at 220GHz you can't have that since your wavelength is so short; you'd just be making a giant resonator instead.

	▲	IndrekR an hour ago \| parent \| next [-]
		Length of this capacitor is close to half-wavelength of 220 GHz (in vacuum). Using siblings of this broadband capacitor (40 GHz, same package) in some designs. In assembly, those require decent process control. This 0201M package is closer to 01005 passives in pad size. Typically no solder paste is used, just flux. Solder mask alignment has to be very tight (thin web used as a dam only). Cost per cap is reasonable where it is actually needed, other parts of the system are often orders of magnitude more expensive at those frequencies where performance matters. Where it gets the very high performance, is pillars/channels etched into silicon quite similar to how DRAM capacitors are made, just a “little bit bigger”. This allows for very low inductance and thus very high resonant frequency.
	▲	Eduard an hour ago \| parent \| prev [-]
		ECM = Embedded Capacitance Material. It is a special PCB laminate designed to create capacitance inside the PCB stack-up, typically between closely spaced power and ground planes.

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matherial 2 hours ago | parent | prev [-]

No, not if you want 22 nF. That's a pretty substantial capacitance. It would need to be quite big on a PCB. That would mean significant inductance, and thus, bad performance at high frequencies.