The present application discloses a semi-floating gate device. A floating gate structure covers a selected area of a first well region and is used to form a conductive channel. The floating gate structure further covers a surface of a lightly doped drain region, and a floating gate material layer and the lightly doped drain region contact at a dielectric layer window to form a PN structure. A source region is self-aligned with a first side surface of the floating gate structure. A first control gate is superposed on a top of the floating gate structure. A second control gate is disposed on a surface of the lightly doped drain region between the drain region and a second side surface of the floating gate structure. The first control gate and the second control gate are isolated by an inter-gate dielectric layer.