Per IRS Publication 17 Your Federal Income Tax (For Individuals), page 25:
Qualifying Widow(er) With Dependent Child
If your spouse died in 2015, you can use married filing jointly as your filing status for 2015 if you otherwise qualify to use that status. The year of death is the last year for which you can file jointly with your deceased spouse.
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 have not remarried, you may be able to use this filing status for 2015 and 2016.
This filing status entitles you to use joint return tax rates and the highest standard deduction amount (if you do not itemize deductions). It doesn't entitle you to file a joint return.
Eligibility rules. You are eligible to file your 2015 return as a qualifying widow(er) with dependent child if you meet all of the following tests.