The qualifying widow(er) filing status allows you to use joint return tax rates and the highest standard deduction amount (if you do not itemize deductions). However, you are not able to file a joint return.
You may be eligible to use qualifying widow(er) with dependent child as your filing status for 2 years following the year your spouse died. For example, if your spouse died in 2014, and you haven't remarried, you may be able to use this filing status for 2015 and 2016.
Please see the IRS
Filing Status Publication for more information.