BottomSheet DialogFragment opens up in STATE_COLLAPSED by default. Which can be forced to open to STATE_EXPANDEDand take up the full device screen with help of the following code template.

@NonNull @Override

public Dialog onCreateDialog(Bundle savedInstanceState) {

    BottomSheetDialog dialog = (BottomSheetDialog) super.onCreateDialog(savedInstanceState);

    dialog.setOnShowListener(new DialogInterface.OnShowListener() {
        @Override
        public void onShow(DialogInterface dialog) {
            BottomSheetDialog d = (BottomSheetDialog) dialog;

            FrameLayout bottomSheet = (FrameLayout) d.findViewById(android.support.design.R.id.design_bottom_sheet);
            BottomSheetBehavior.from(bottomSheet).setState(BottomSheetBehavior.STATE_EXPANDED);
        }
    });

    // Do something with your dialog like setContentView() or whatever
    return dialog;
}

Although dialog animation is slightly noticeable but does the task of opening the DialogFragment in full screen very well.