The SplineArea chart is just like the area chart with the only difference in the manner in which data points are connected.  The SplineArea chart connects data points by using splines instead of straight lines, and fills the area enclosed by the splines.

You can set the ChartType property to SplineArea to create the SplineArea Chart.

To create the stacking SplineArea Chart, set the Stacking property to Stacked or Stacked100pc.