how to close excel application open by vb.net code.

how to close excel application open by vb.net code. When I quit application in my code.. It still running in task manager.. this is my code

Dim xlApp As Excel.Application
Dim xlWorkBook As Excel.Workbook
Dim xlWorkSheet As Excel.Worksheet

xlApp = New Excel.ApplicationClass
xlWorkBook = xlApp.Workbooks.Add(misValue)
xlWorkSheet = xlWorkBook.Sheets("sheet1")

.......................write in excel sheet..........

xlWorkBook.SaveAs(filepath, Excel.XlFileFormat.xlWorkbookNormal, misValue, misValue, misValue, misValue, Excel.XlSaveAsAccessMode.xlExclusive, misValue, misValue, misValue, misValue, misValue)
xlWorkBook.Close(True, misValue, misValue)
xlApp.Quit()