Superconducting field effect transistor

A superconducting field effect transistor, comprising:

• a semiconductor substrate;
• first and second impurity-doped regions formed in the semiconductor substrate;
• first and second superconducting electrodes formed on the semiconductor substrate;
• a gate electrode formed over a region of the semiconductor substrate, with an insulating film therebetween, said gate electrode being interposed between said first and second superconducting electrodes, the gate electrode being formed of a first layer of a first material, and a second layer, different in material from the first layer formed on top of said first layer, wherein side surfaces of said second layer which oppose said first and second superconducting electrodes extend further along a distance between said first and second superconducting electrodes than side surfaces of said first layer which oppose said first and second superconducting electrodes;
• wherein said first material is poly-silicon, and said second material is silicon nitride.

A superconducting field effect transistor, comprising

• a semiconductor substrate;
• first and second impurity-doped regions formed in the semiconductor substrate;
• first and second superconducting electrodes formed on the semiconductor substrate;
• a gate electrode formed over a region of the semiconductor substrate, with an insulating film therebetween, said gate electrode being interposed between said first and second superconducting electrodes, the gate electrode being formed of a first layer of a first material, and a second layer, different in material from the first layer formed on top of said first layer, wherein said surfaces of said second layer which oppose said first and second superconducting electrodes extend further along a distance between said first and second superconducting electrodes than side surfaces of said first layer which oppose said first and second superconducting electrodes;
• wherein a region of said semiconductor substrate between said first and second impurity-doped regions projects above a top surface of said first and second impurity-doped regions, and wherein said first and second impurity-doped regions, the first and second superconducting electrodes and the gate electrode are formed so that the projecting region of said semiconductor substrate acts as a channel region.

A superconducting field effect transistor comprising;

• a semiconductor substrate;
• first and second impurity-doped regions formed in the semiconductor substrate;
• first and second superconducting electrodes formed on the semiconductor substrate;
• and
• a gate electrode formed over the semiconductor substrate with an insulating film therebetween and interposed between the first and second superconducting electrodes, the gate electrode being formed of a poly-silicon layer and a silicon nitride layer formed on the top of the poly-silicon layer, wherein a width of the silicon nitride layer extending in directions opposing said first and second superconducting electrodes, is greater than a width of the poly-silicon layer.

A superconducting field effect transistor comprising;

• a semiconductor substrate;
• first and second impurity-doped regions formed in the semiconductor substrate;
• first and second superconducting electrodes formed on the semiconductor substrate;
• and
• a gate electrode formed over the semiconductor substrate with a first insulating film therebetween, said gate electrode being interposed between the first and second superconducting electrodes, side surfaces of said gate electrode opposing said first and second superconducting film being coated with a second insulating film.