If you look for an inverter circuit on Google Images, you'll find something that looks like this:

[![enter image description here](https://i.stack.imgur.com/vKhN6.png)](https://i.stack.imgur.com/vKhN6.png)

This inverter design has a single NPN transistor. However, on Wikipedia's article about transistor count, inverters are listed as having two transistors. Wikipedia states that this number is based off of CMOS technology, and if you search for a CMOS inverter, you get this image instead.
[![enter image description here](https://i.stack.imgur.com/nDBAS.png)](https://i.stack.imgur.com/nDBAS.png)
This design does have two transistors: one PNP and one NPN MOSFET. However, I've always been perplexed as to why people do not use the former method for chip manufacturing. After all, Wikipedia would not have stated that inverters required two transistors if the first method was widely used in making chips. Why is there a difference between the CMOS and the BJT method of creating a circuit as simple as a NOT gate?