Epitaxial 50 nm and 200 nm thick films of Pb(Zr0.40Ti0.60)O-3 (PZT) have been deposited by reactive rf magnetron sputtering on conductive Nb-doped SrTiO3(100) (STO). The patterning process involved electron beam lithography of polymethylmethacrylate (PMMA), fabrication of a 75 nm thick Cr hard mask layer by means of a lift off process, and dry etching of PZT. The smallest PZT features obtained by means of this process were 50 nm in lateral dimensions. Piezoelectric sensitive scanning force microscopy in the contact mode revealed a strong increase of the piezoelectric response for feature sizes with lateral dimensions below 300 nm (200 nm film). It is proposed that this behavior is mainly due to vanishing a-domains.