MEMORY DEVICE AND MANUFACTURING METHOD THEREOF

A method includes sequentially depositing a floating gate layer, a dielectric structure stack, and a control gate layer over a substrate. A first etching process is performed to pattern the control gate layer, the dielectric structure stack, and a top portion of the floating gate layer to form a control gate, a dielectric structure, and a top portion of a floating gate over a bottom portion of the floating gate layer. A sidewall of the top portion of the floating gate is concave. A first spacer structure is formed on the sidewall of the top portion of the floating gate, a sidewall of the dielectric structure, and a sidewall of the control gate. A second etching process is performed to pattern the bottom portion of the floating gate layer to form a bottom portion of the floating gate after forming the first spacer structure.