There are provided a gate electrode formed on a semiconductor substrate of one conductivity type via a gate insulating film, ion-implantation controlling films formed on both side surfaces of the gate electrode and having a space between the gate electrode and an upper surface of the semiconductor substrate, first and second impurity diffusion regions of opposite conductivity type formed in the semiconductor substrate on both sides of the gate electrode and serving as source/drain, a channel region of one conductivity type formed below the gate electrode between the first and second impurity diffusion regions of opposite conductivity type, and pocket regions of one conductivity type connected to end portions of the impurity diffusion regions of opposite conductivity type in the semiconductor substrate below the gate electrode and having an impurity concentration of one conductivity type higher than the channel region.