The number has some connection to transistor density, in the sense that a lower number means generally higher density. However there is not any physical feature on the chip that is actually 3nm in length.
This has been true since the late 90s probably.
avidamoeba@lemmy.ca 3 weeks ago
It is marketing and it does have meaningful connection to the litho features, but the connection is not absolute. For example Samsung’s 5nm is noticeably more power hungry than TSMC’s 5nm.