Need an inverted semicircle as an accent mark over a character

I need to write a macro (something like semicircle{{#1}} )
to place an inverted semicircle symbol as an accent mark to be placed over a character, using a stackrel comand.
The frown symbol is too flat, and the cap symbol is too tight, so the choice is a down facing side semicircle sitting
opve rthe character(s).
The semicircle should spreard over all the characters (one or two) that are placed for #1 in the macro – something like semicircle{X} or semicircle (XY} etc.
Is TikZ a good choice?
Any help in building such a macrio will be apprecieated.