It is common when the curved surface is connected with a planar surface, as the corner needs much finer triangles to mesh it.
The property “max refine steps” in "mesh" tab determines how many iterations are allowed during the mesh refinement process. Sometimes, the default number is not large enough for the refinement to finish within the allowed number of iterations. In such a case, the refining will stop before the mesh becomes fine enough to capture the variation in the doping or optical generation profile. The solver then generates a warning message saying that the mesh is not refined enough.
The easiest way to solve this problem is to increase the value of “max refine steps” so that the solver gets the opportunity to properly refine the mesh and the warning should go away. You can learn about the different parameters that CHARGE uses in calculating the mesh from https://optics.ansys.com/hc/en-us/articles/360034918633-CHARGE-solver-Simulation-object
Since 2D has this issue, 3D will be more challenge. You could try to ass small edged ring around this interface to replease the strict meshing requirement.
you can imaging in real device it will not be the perfect geometry. You may simulate half of the structure depending on where the contacts are located.