Abstract: An improved method of constructing a semiconductor device of the encapsulated type wherein a stack of members including a semiconductor element is encapsulated along with spring means ensuring compressive contact to the element contact areas. Hitherto up to five spring washers were needed to keep total spring deflection to within a value giving a desired compressive force, due to accumulated thickness tolerances of the stack members. In the present invention, a plastically deformable member is included in the stack initially along with a thickness gauge member such that bringing together the encapsulation housing parts round the stack flattens a single included spring washer and deforms the deformable member by a certain extent. This certain extent is such that when the stack is re-assembled without the thickness gauge, the plastically deformable member is now of a thickness to cause the spring to deform by an amount giving a desired compression force in the finished stack.