Semiconductor integrated circuit device and method for manufacturing semiconductor integrated circuit device

A method for manufacturing a semiconductor integrated circuit device, comprising the steps of:

• (a) forming an element isolation region in the surface of a first main surface of a semiconductor wafer to define an N channel active region and an adjacent P channel active region in the surface of the first main surface of the semiconductor substrate;
• (b) forming, over the first main surface of the semiconductor substrate, an N channel gate stack that traverses the N channel active region and constitutes an N channel MISFET;
• (c) forming, over the first main surface of the semiconductor substrate, a P channel gate stack that traverses the P channel active region and constitutes a P channel MISFET;
• and
• (d) prior to the steps (b) and (c) but after the step (a), forming an N channel threshold voltage adjusting element outward diffusion preventing region in the surface region of the element isolation region below and at the periphery of the N channel gate stack,
• wherein the N channel threshold voltage adjusting element outward diffusion preventing region is formed by depositing an N channel threshold voltage adjusting element or oxide thereof over a portion of the surface of the element isolation region which is to be the N channel threshold voltage adjusting element outward diffusion preventing region, and heat treating a resulting film,
• wherein the N channel threshold voltage adjusting element outward diffusion preventing region is formed without forming the N channel threshold voltage adjusting element outward diffusion preventing region in the surface region of the element isolation region below and at the periphery of the P channel gate stack,
• wherein the N channel threshold voltage adjusting element or oxide thereof is any of La, Y, Mg, Sc, or oxides thereof,
• and wherein step (d) is performed without introducing the N channel threshold voltage adjusting element into the N channel active region.