Rounded modal bottom sheet as seen in new Google products(Tasks, News, etc.), described in this article: https://medium.com/halcyon-mobile/implementing-googles-refreshed-modal-bottom-sheet-4e76cb5de65b

bg_bottom_sheet_dialog_fragment.xml

<!-- Drawable used for the bottom sheet dialog background -->
<?xml version="1.0" encoding="utf-8"?>
<shape xmlns:android="http://schemas.android.com/apk/res/android"
    android:shape="rectangle">
    <corners
        android:topLeftRadius="@dimen/bottom_sheet_corner_radius"
        android:topRightRadius="@dimen/bottom_sheet_corner_radius" />
    <padding android:top="@dimen/bottom_sheet_top_padding" />
    <solid android:color="@color/primary" />
</shape>

dimens.xml

<dimen name="bottom_sheet_corner_radius">16dp</dimen>
<dimen name="bottom_sheet_top_padding">8dp</dimen>

RoundedBottomSheetDialogFragment.kt

package com.your.package

import android.app.Dialog
import android.os.Bundle
import com.your.package.R
import com.google.android.material.bottomsheet.BottomSheetDialog
import com.google.android.material.bottomsheet.BottomSheetDialogFragment

/**
 * BottomSheetDialog fragment that uses a custom 
 * theme which sets a rounded background to the dialog 
 * and doesn't dim the navigation bar
 */
open class RoundedBottomSheetDialogFragment : BottomSheetDialogFragment() {

    override fun getTheme(): Int = R.style.BottomSheetDialogTheme

    override fun onCreateDialog(savedInstanceState: Bundle?): Dialog = BottomSheetDialog(requireContext(), theme)

}

styles-v21.xml

<!-- v21 styles, you can merge these two if your minSdkVersion is >= 21 -->
<resources>
  
    <style name="BottomSheetDialogTheme" parent="BaseBottomSheetDialog">
        <item name="android:statusBarColor">@android:color/transparent</item>
        <item name="android:navigationBarColor">@color/white</item>
    </style>
  
</resources>

styles.xml

<resources>
    
  <!-- set the rounded drawable as background to your bottom sheet -->
    <style name="BottomSheet" parent="@style/Widget.Design.BottomSheet.Modal">
        <item name="android:background">@drawable/bg_bottom_sheet_dialog_fragment</item>
    </style>

    <style name="BaseBottomSheetDialog" parent="@style/Theme.Design.Light.BottomSheetDialog">
        <item name="android:windowIsFloating">false</item>
        <item name="bottomSheetStyle">@style/BottomSheet</item>
    </style>

    <style name="BottomSheetDialogTheme" parent="BaseBottomSheetDialog" />
  
</resources>