Abstract: A semiconductor device is provided, which is capable of high-speed operation of MOSFETs in a device section while suppressing the current leakage of MOSFETs in another device section even if the device is further miniaturized. This device is comprised of a semiconductor substrate, a first section defined on the substrate, a second section defined on the substrate, and a dielectric masking layer covering the first section while uncovering the second section. The first section includes a first MOSFET with a first pair of source/drain regions, a first gate insulating layer formed on the substrate, and a first gate electrode formed on the first gate insulating layer. No silicide layer is incorporated in each of the first pair of source/drain regions. The first MOSFET is covered with the masking layer in such a way that the first pair of source/drain regions of the first MOSFET are contacted with the masking layer.