Now just to expand our thinking a bit, there are other ways that preservation may take place. Shown here is an insect trapped in amber (a tree sap substance), petrifaction, embalming, freezing and mummification. But this are much less frequent than permineralization fossils.
Photo Credits:
Montage adapted from C. Walker and D. Ward, Eyewitness Handbook of Fossils, Dorling Kindersley, Inc, New York, 1992, pgs.12-13
Petrified Wood: https://www.juniorgeo.co.uk/images/Petrified-Wood.jpg