How to 'fill' the space between two parametric curves.

Good morning,


I'm trying to make an S shape drawing to my model that consists in two rectangles and 4 parametric curves ( forming 2 semi-circles).
But when I make the extrusion the parametric part of the drawing doesn't come out as a solid, but rather as a line.

How can I make my extrusion for the S shape part.


I'm uploading a copy of my model so may take a look .


Thank you very much.