A semiconductor memory device and method of erasing data are disclosed. In one example, a semiconductor memory device includes a block including a plurality of pages and a controller that controls writing, erasing, and reading of data. Each of the pages includes a plurality of memory cells each being changeable to a number of states. In a case of erasing only a partial page of the plurality of pages, the controller overwrites the partial page with predetermined data that causes state change only by one stage.