Can't get transparent DialogFragment

I have a dialog Fragment which look like that.

AlertDialog ad = builder.create();
Drawable d = new ColorDrawable(Color.BLACK);
d.setAlpha(130);
ad.getWindow().setBackgroundDrawable(d);

This code get background semi transparent. But I still got a white part on the bottom. I want to get rid of the white to just have semi transparent background

I already tried a lot of stuff that I saw in other posts.

I don't know what is the object that I must change between the DialogFragment, the AlertDialog and the LinearLayout.

It may not be the LinearLayout, because when I increase margin, nothing is moving.

Here is my code :

@Override
public Dialog onCreateDialog(Bundle savedInstanceState) {
//      setStyle(DialogFragment.STYLE_NORMAL, 0);
//      setStyle(STYLE_NO_FRAME, R.style.CustomDialog);
//      setStyle(STYLE_NO_FRAME, 0);
    AlertDialog.Builder builder = new AlertDialog.Builder(getActivity());
    View view = getActivity().getLayoutInflater().inflate(
            R.layout.share_or_die, null);

    AlertDialog ad = builder.create();
    Drawable d = new ColorDrawable(Color.BLACK);
    d.setAlpha(130);
    ad.getWindow().setBackgroundDrawable(d);
    ad.setCanceledOnTouchOutside(true);
    ad.getWindow().requestFeature(Window.FEATURE_NO_TITLE);

    ad.getWindow().setFlags(WindowManager.LayoutParams.FLAG_FULLSCREEN, WindowManager.LayoutParams.FLAG_FULLSCREEN);      

    return ad;

}

I just call it in the mainActivity when user click back button:

@Override
public void onBackPressed() {
        if (isUserConnected && !hasShared) {
        shareOnExitDialog = new ShareOnExitDialog();
            shareOnExitDialog.setCancelable(true);
            shareOnExitDialog.show(getSupportFragmentManager(), "Exit");
        } else {
            finish();
        }


}

Any help would be appreciated !