Semiconductor device

A semiconductor device having at least first and second field effect transistors:

• said first field effect transistor having:
• a p-type semiconductor region;
• an n-type source region and an n-type drain region, having a maximum surface impurity concentration of 10.sup.18 but lower than 10.sup.20 cm.sup.-3, formed spaced apart from each other in said p-type semiconductor region, the source and drain regions being spaced from the surface of the p-type semiconductor region;
• first and second conductive layers disposed on said n-type source region and said n-type drain region respectively;
• at least one of said first and second conductive layers being of a material selected from the group consisting of a refractory metal and silicide of said refractory metal;
• at least one high impurity concentration semiconductor layer in said p-type semiconductor region and extending to the surface thereof, respectively extending between at least one of the source and drain regions and said at least one of the first and second conductive layers, and ensuring ohmic contact between said at least one of the n-type source and n-type drain regions and said at least one of the first and second conductive layers, the at least one high impurity concentration semiconductor layer being of n-type conductivity and having a higher impurity concentration than that of the respective n-type source region or n-type drain region, the at least one high impurity concentration semiconductor layer having a thickness not exceeding 50 nm;
• and
• first gate means on a first channel region defined between said n-type source region and said n-type drain region;
• said second field effect transistor having;
• an n-type semiconductor region;
• a p-type source region and a p-type drain region, having a maximum surface impurity concentration of 10.sup.17 to 10.sup.19 cm.sup.-3, formed spaced from each other in said n-type semiconductor region;
• third and fourth conductive layers disposed on said p-type source region and said p-type drain region, respectively;
• and
• second gate means on a second channel region defined between said p-type source region and said p-type drain region.

A semiconductor device comprising:

• a semiconductor region of a first conductivity type;
• a source region and a drain region, each of a second conductivity type which is opposite to said first conductivity type, separately disposed in said semiconductor region of the first conductivity type and spaced from the surface thereof, the maximum surface impurity concentration in at least one of said source region and said drain region being equal to or higher than 10.sup.18 cm.sup.-3 but lower than 10.sup.20 cm.sup.-3 ;
• first and second conductive layers of a material selected from a group consisting of a refractory metal and a silicide of said refractory metal, disposed respectively on the source and drain regions;
• first and second segregated layers, of said second conductivity type, having a higher impurity concentration than that of the respective source region or drain region and having a thickness not exceeding 50 nm, extending in said semiconductor region of a first conductivity type to the surface thereof, respectively between the source and drain regions and the first and second conductive layers;
• and
• a gate means on a region of said semiconductor region of a first conductivity type between said source region and said drain region.