PURPOSE: To form a short gate length of an FET by forming a window opening of a predetermined diameter in a position where a gate of a semiconductor substrate coated with photoresists of two layers having different sensitivities is formed, and forming a gate of a predetermined length on the substrate by using a metal mask in the window opening formed by obliquely depositing the metal from above the photoresist.

CONSTITUTION: A low sensitivity photoresist 5b and a high sensitivity photoresist 5c are build up on a substrate 1 through an insulating film 4. A window opening 5d of a predetermined diameter is formed in a position where a gate of the substrate 1 is formed, and a lift-off step 5e is further formed near the opening 5d of the upper photoresist 5c. Then, a mask metal is deposited obliquely in direction A from above the photoresist 5c, and the continuous surface from one side inner wall 5d1 to become a deposited surface in the opening 5d to a predetermined position P on the film 4 is covered with a metal mask 7. Thereafter, after the film 4 in the opening 5d is opened, a gate metal 6 is deposited, and a gate G0 of a predetermined length L0 is formed in a predetermined position on the substrate 1.