Unable to fully close Excel - window is closed, but it remains in process manager

[amalanov]

In order to close Excel I do the following

    if (this.excel && this.excel.Workbooks.Count !== undefined && this.excel.Workbooks.Count === 0){
        this.logger("All workbooks are closed. Close Excel also.");
        this.getExcel().DisplayAlerts = false;
        this.getExcel().Quit();
        this.excel = undefined;
    }

but it remains in system monitor.