A tax return is likely required for your deceased spouse. Married filing jointly would, in most cases, be the filing status you would want to use if you did not remarry before December 31st.
Spouse died during the year. If your
spouse died during the year, you are considered
married for the whole year for filing status
purposes.
If you didn't remarry before the end of the
tax year, you can file a joint return for yourself
and your deceased spouse.
In other words, you would also have to file using the married filing separately status (exception above). You can use the IRS Transcript free online system to obtain your prior filings or you can contact the IRS for your deceased spouse information from a joint tax return from the past years. IRS Get Transcript