Geometric correction in mountain areas


I used SNAP tool to apply terrain correction to a couple of sentinel-1A IW (GRDH), for multi-temporal analysis using intensity.

As you can see from the two images (they refer to the same date, but scenes at both dates have the same problems), I obtain very different results from flat and mountain areas. I used a 10m resolution DEM (result is, of course, even worse using the default SRTM).
Is there a way to improve these results??

I applied this workflow: applied orbit (images of october 2014 and november 2014), calibrated, speckle filtered, terrain corrected and co-registered. Can you tell me if this is a correct way to proceed???
Thank you.

I don’t quite follow your problem. In high terrain areas there is going to be effects of layover, foreshortening and shadow. What you see here is the results of the interpolation over these areas. If you are using your own external dem, you need to make sure it accounts for the Earth’s gravitational model.