shaded up and down of a TF1

Hello,

i was wondering how to make a TF1 function that would have filled area but : -only to a certain given extension (not till y=0) -with a filled ared up and down to a given extension

here is attached a typical example that i copied/pasted from a talk of a meeting (which most probably is using a TGraph)

-->i would like to do this with a TF1. Most probably an "erf" function would
modelize the function, but the main problematic point is the shaded area. And the SetLineWidth has a limitation for the width

thanks for any advice

thougthfully