What it takes to Fabricate an IC

What it takes to fabricate an IC of a very basic electronics circuit? The input is a signal (signals) from a remote controller and the output is a sound. If it is feasable how small the whole thing can be? (without the remote). I need it to be as tiny as possible. Thanx for the help.

An iC with one input and one audio out is possible, but what function is needed defines if it is technical visibale and how big it is in chip size, which defines the package. Small packages these days are 2mm x 2mm (like iC-DX).

Enjoy your design work!

As tiny as possible would be a bumped die with 4 pads
in "chip scale packaging" (i.e. just some sort of coating)
and that would come in about 0.5mm on a side at the
more aggressive end (200um bump pitch). That will be
quite the challenge to handle for your PCB assembler,
liable to get sucked right up the vacuum wand.

So call the chip itself a probable don't-care, smaller
most likely than the passives which will surround it.
Presuming your circuitry fits in the minimal frame.
Which wants you to think more about what can be
handled by the manufacturing flow downstream; you
may in fact want packaged (say hello to more tooling
charges for anything aggressive, though there are
outfits selling open-tooled small outline prototyping
packages, and hiring some assembly house to bond
it up after hitting you for NRE charges).

Mainly what it takes is a pile of cash. You will not be
doing any of they physical work yourself, and vendors
are all about the paycheck.