Abstract: A method of fabricating a lightly doped drain MOSFET device with a built in etch stop is disclosed. After forming a gate electrode on a substrate through conventional methods, a conformal doped layer is deposited on the gate electrode. A conformal layer of nitride is then deposited on the conformal doped layer. The nitride layer is etched, with the etch stopping on the conformal doped layer, thereby forming nitride spacers. Deep source and drain regions are formed by either ion implantation or diffusion. The device is then heat treated so that light diffusion occurs under the nitride spacers and heavy diffusion occurs outside the spacer region. The method is applicable to N-substrate (P-channel), P-substrate (N-channel), and complementary metal oxide semiconductor (CMOS) devices.