EXHIBIT 12.1

                   CERTIFICATION OF CHIEF EXECUTIVE OFFICER


I, Dr. Wolfgang Ziebart, certify that:

1.    I have reviewed this annual report on Form 20-F of Infineon Technologies
      AG (the "Company");

2.    Based on my knowledge, this annual report does not contain any untrue
      statement of a material fact or omit to state a material fact necessary
      to make the statements made, in light of the circumstances under which
      such statements were made, not misleading with respect to the period
      covered by this annual report;

3.    Based on my knowledge, the financial statements, and other financial
      information included in this annual report, fairly present in all
      material respects the financial condition, results of operations and cash
      flows of the Company as of, and for, the periods presented in this annual
      report;

4.    The Company's other certifying officer and I are responsible for
      establishing and maintaining disclosure controls and procedures (as
      defined in Exchange Act Rules 13a-15(e) and 15d-15(e)) for the Company
      and have:

      (a)   designed such disclosure controls and procedures, or caused such
            disclosure controls and procedures to be designed under our
            supervision, to ensure that material information relating to the
            Company, including its consolidated subsidiaries, is made known to
            us by others within those entities, particularly during the period
            in which this report is being prepared;

      (b)   [omitted pursuant to the guidance of Release No. 33-8238 (June 5,
            2003)];

      (c)   evaluated the effectiveness of the Company's disclosure controls
            and procedures and presented in this report our conclusions about
            the effectiveness of the disclosure controls and procedures, as of
            the end of the period covered by this report based on such
            evaluation; and

      (d)   disclosed in this report any change in the Company's internal
            control over financial reporting that occurred during the Company's
            most recent fiscal quarter that has materially affected, or is
            reasonably likely to materially affect, the Company's internal
            control over financial reporting;

5.    The Company's other certifying officer and I have disclosed, based on our
      most recent evaluation of internal control over financial reporting, to
      the Company's auditors and the audit committee of Company's board of
      directors (or persons performing the equivalent functions):

      (a)   all significant deficiencies and material weaknesses in the design
            or operation of internal control over financial reporting which are
            reasonably likely to adversely affect the Company's ability to
            record, process, summarize and report financial information; and

      (b)   any fraud, whether or not material, that involves management or
            other employees who have a significant role in the Company's
            internal controls over financial reporting.

Date:  November 26, 2004

                                      /s/ Wolfgang Ziebart
                                      ----------------------------------
                                      Dr. Wolfgang Ziebart
                                      Member of the Management Board and
                                      Chief Executive Officer