I won't go home until I finish my homework.
= I will go home (after finishing) my homework.
1.原句意为“直到我做完作业,我才会回家”,同义句句意为“做完作业后我将回家”,after finishing my homework为介词加上动名词短语形成的介宾短语；
2.一楼答案有误,如果直接用until/till,意思是“我会一直回家,直到做完作业后”,后者句意不通.因为until/till的主句如果是肯定句,则要求谓语动词为延续性动词,而go home为瞬间限动词.