A transistor includes a source region, a drain region, a channel region, a gate electrode and a layer of a stress-creating material. The stress-creating material provides a stress that is variable in response to a signal acting on the stress-creating material. The layer of stress-creating material is arranged to provide a stress in at least the channel region. The stress provided in at least the channel region is variable in response to the signal acting on the stress-creating material. Layers of stress-creating material providing a stress that is variable in response to a signal acting on the stress-creating material may also be used in circuit elements other than transistors, for example, resistors.