to the diffraction effect of the exposure light rounded patterned is resulted for the photoresist layer 230 assuming that the length and pitch in x direction are the same as the width and pitch in y direction for both the photoresist layers 220 and 230 and each block of the photoresist layer 230 overlying the center four neighboring blocks of the photoresist layer 220 openings 240 are formed without rounded comers as shown in fig1 b this is because that the width of the blocks is larger than the pitch and the openings 240 defined by the pitches of the superposing photoresist layers 220 230 have width and length smaller than the blocks the rounded comers of the photoreist layers 220 and 230 overlap with each other can are thus eliminated with each other 0022 fig2 c shows a cross sectional view of the openings 240 along the cutting line ii ii u2032 of fig2 b using the photoresist layers 220 and 230 the insulation layer 210 is etched to form the contact hole via holes 250 as the openings 240 are defined by the straight lines of the sides of four staggering neighboring blocks of the photoresist layers 220 and 230 the openings 240 are thus formed with rectangular shapes without rounded comers in this embodiment two photoresist layers with patterns of blocks are formed though the blocks are.