If this just for constructibility, and if the fill is relatively stable and workable, e.g. compact or dense condition, groundwater controllable,etc., and your construction equipment is able to reach the bottom of fill, you may have options as:
1. Engineered fill: dig it out and relay it with engineered fill (check with a geotech engr for local specs).
2. Extended footing: construct a steepsided trench down to contact competent native soil, fill up with flowable, lean mix concrete (unshrinkable fill) to the underside of the footing. Due to the different supporting characteristics undercross the footing, transitions in subgrade or structure strengthening should be provided in the footing unit.
3. Piers or short piles.
Again, as others indicated, if data shows the fill is engineered, you do not have to remove it, get a geotechnical firm assess the condition (compactness) and if it is considered competent, you may revise you footing design based on a different soil condition and just leave it there and build your foundation over it, provided that no utilities buried within it and surface improvement carried.
Anyway, a geotechnical engineer should be involved for the site condition.