Create 3d mesh from STL files

Hi,

I would like to know if it's possible to create a clean 3d mesh from an STL file as shown in the image below. I tried the mesh wrap option in 2D and checked the create solid (all tetra) option. But I encountered several problems. The mesh most of the times can jump of the boundaries of the STL file, some elements with very poor quality for FEM analysis are generated (even though I'm using a reasonable size for the elements).
Is there a way to do this?