I've been studying some vlsi lately and came across instances where the author mentioned that it is easier to use MOSFETs at the micron level than it is to use a resistor. Therefore at many instances(such as load inverters) MOSFETs are used in place of resistors.
MOSFETs are complicated silicon devices with various n and p regions whose operation is much more complex than resistors. Reducing their size to micrometers/nano would make the task of creating a MOSFET very complicated and the operation difficult to sustain given the small size of the various regions in a MOSFET. Consdering all this how is it easier to fabricate and use MOSFETs than resistors in IC chips ?