Yes, you will need to get your son's W-2 and file his tax return if his gross income required him to file a tax return for 2020.
A single filer is required to file a tax return if the gross income is at least $12,400, please see Do I need to file a federal return this year? for additional details. Even if your son was not required to file a return this year, you might want to file one anyway to recover any 2020 federal tax withheld from his paychecks.
Please see Can I e-file a tax return for someone who is deceased? and IRS Deceased Persons – Filing the Final Return for additional information.
Please accept my condolences for the loss of your son.
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