A flash memory using hot carrier injection and a method of operating the same are provided. A plurality of strings constituting a page are formed on a single p-well and share the p-well. During a program operation, a string selection transistor is turned off, and electrons are accumulated in a source or drain region in response to a bias voltage applied to the p-well. Thereafter, the accumulated electrons are trapped in a charge trap layer of a memory cell in response to a program voltage applied through a word line. Also, during an erase operation, holes accumulated in response to a bias voltage applied to the p-well are trapped in the charge trap layer in response to an erase voltage. The flash memory performs NAND-type program and erase operations using hot carrier injection.